In order to discover, scientists sometimes have to invent. Consider the devices Faraday had to build in order to explore electricity and magnetism. On a larger scale, consider Ernest O. Lawrence's invention of the cyclotron, which made it possible to explore the universe of elementary particles at new levels of precision and depth (Kevles, 1977).
Edison, the archetypal inventor, said, "in truth, we electricians are discoverers, not inventors" (Baldwin, 1995). If Edison is right, inventors sometimes have to discover. For example, when experiments with a glider in 1901 failed to meet expectations, the Wrights constructed a wind tunnel and disconfirmed the widely-accepted value for the coefficient of lift. In order to invent an airplane, they had to discover new coefficients (Crouch, 1992).
In the last chapter, we spoke of the discoverer as hero. Inventors, especially in America, are often painted in the same mythic colors. In both cases, the focus is on the flash of insight that shows the discoverer the key to nature, or the inventor how to transform the world. Although scientific publications and awards now recognize multiple discoverers, the idea of the solitary inventor lies at the basis of the American patent system, and juries in patent disputes are still impressed by stories of solitary inventors who have a flash of insight (Seabrook, January 11, 1993). "A common perception of the inventor includes terms such as weird, individualistic, wild-eyed, odd, socially inept, and quixotic" (Colangelo, Assouline, Kerr, Huesman, & Johnson, 1993, p. 160). Nikola Tesla is the inventor who comes closest to fitting this portrait, with his Wizard-like abilty to produce surprising electrical effects and his eccentric personal habits (Wise, 1994).
In contrast, the 34 agricultural inventors in Colangelo's study were happy, hard-working people whose only eccentricity was that when a problem captured them, they had to put off everything else and work on it. This kind of obsession also characterized Edison, who both tried to cultivate the notion that he was a Wizard and dispel it with remarks like 'invention is 1% inspiration and 99% perspiration'. As he said, "No experiments are useless." (Baldwin, 1995, p. 51).
While scientists may have to invent and inventors discover, one could argue that each is pursuing a different goal. The scientist wants to be able to explain a phenomenon, the inventor simply to produce it, reliably. Children may focus on getting positive results on tasks that simulate scientific reasoning because they adopt an engineering goal, rather than a scientific one: they become more concerned with producing an effect than understanding the mechanisms behind it (Schauble, Klopfer, & Raghavan, 1991).
The same kinds of battles over priority that characterize science also characterize invention, but whereas in the former, disputes are mediated by organizations like the Nobel Prize Committee, in the latter, they are settled by the legal system.
To get a better understanding of the similarities and differences between discovery an invention, we will adopt a case-based approach to understanding invention, spending much of the chapter considering the invention of the telephone in fine-grained detail, then seeing if our conclusions generalize to other inventions and to the discoveries we discussed in the first chapter. Recent research on case-based reasoning and situated and distributed cognition suggests that experts learn from examples (Kolodner, 1993). Instead of treating this cognitive research in a separate chapter, as we did with the cognitive psychology of science, we will review relevant portions of this new work as we consider cases. This is a reflexive application of the case-based approach to a discussion of the case-based approach, and carries with it the dangers we referred to at the beginning of the last chapter. Let us keep that in mind as we go forward.
In a press conference on the 23rd of March, 1989, Stanley Pons and Martin Fleischmann, two scientists working in relative isolation with comparatively simple equipment, announced the discovery of the holy grail of energy researchers: an apparently limitless, pollution free source of power. This was the beginning of the most recent and spectacular controversy over the possible existence of cold fusion, though it was by no means the first (Close, 1991). Initially, it looked like a classic Campbellian hero's tale, a paradigm-busting experiment that signaled a new scientific revolution.
The reigning paradigm in fusion research involved multi-million dollar technologies like tokamaks, or toroidal magnetic chambers, that achieve temperatures higher than the center of the sun in an effort to fuse hydrogen into helium. The problem is that more energy is used in creating these conditions than results from the fusion. Pons and Fleischmann's experiments at the University of Utah gave hope that fusion could be created and sustained with a few thousand dollars worth of equipment.
Basically, their 'cold fusion tokamak' was an electrolysis cell with a palladium rod down the center, used to separate deuterium from ordinary water. The two researchers knew that palladium has a natural affinity for hydrogen and that the deuterium would therefore migrate into the palladium. They theorized that inside the crystal lattice of the palladium, the hydrogen would be under very high pressure-perhaps enough pressure to produce fusion. Their initial experiments suggested that this palladium cell produced an excess of heat--in one case, enough to cause the cell to explode, fortunately when no one was nearby. Here was a triumph of little science over big science.
Pons and Fleischmann weren't the only researchers to discover cold fusion. Stephen Jones, at rival Brigham Young University, had also conducted experiments that demonstrated cold fusion. Jones found out about Pons and Fleischmann's work when he was asked to referee one of their grant proposals. Initially, both research teams agreed to submit simultaneous papers to Nature. Jones was also about to present his results at a scientific conference, and Pons and Fleischmann felt sure he would be given priority as the discoverer if they did not pre-empt him. Furthermore, they felt that Jones had stolen their idea. Therefore, Pons and Fleischmann decided to announce their discovery at a press conference, rather than in a refereed journal.
These disagreements about priority and credit were intensified by the fact that cold fusion was more than a scientific discovery--it was also an invention that could make the researchers and the universities they worked for wealthy. There were important differences between Jones and Pons and Fleischmann's work that made the former less likely to be an invention than the latter. Jones had detected neutron levels slightly above the background with his cell, suggesting that fusion might be causing the neutron emissions, but at a level too low to be a significant source of power. Indeed, he detected no rise in temperature. Pons and Fleischmann, on the other hand, had detected a significant rise in temperature, but not the concomitant excess of neutrons one would have expected. Nuclear physicists who saw pictures of Pons and Fleischmann standing next to their palladium cell while it was operating said they should have been killed by the radiation. As one scientist noted after seeing a Cable Network News report, "the man explaining the experiment to the reporters was apparently touching the glass bulb containing the active elements and yet none of his bodily parts fell off" (Close, 1991, p. 163).
Scientific teams all over the world set out to replicate Pons and Fleischmann's experiments, but critical details of the procedure were hard to come by, partly because the University was submitting patent applications for the process (Huizenga, 1992). Before Congress, Ronald Ballinger of MIT's Plasma Fusion Center testified that, "The level of detail concerning the experimental procedures, conditions and results necessary for verification of the Fleischmann and Pons results have not been forthcoming. At the same time, almost daily articles in the press, often in conflict with the facts, have raised the public expectations, possibly for naught, that our energy problem has been "solved". We have heard the phrase "too cheap to meter" applied to other forms of electric enery production before. And so the scientific community has been left to attempt to reproduce and verify a potentially major scientific breakthrough while getting the experimental details from The Wall Street Journal and other news publications" (Close, 1991, p. 189). James Brophy of the University of Utah lamented that, "The scientists want us to tell everything but the patent attorneys tell us to say absolutely nothing" (Close, 1991, p. 191). Similarly, Fleischmann argued that "we had written a number of patents by that stage and the view of the university was that we should announce this by a press conference. It was really the patents that were driving this" (Close, 1991).
Withholding information prior to obtaining a patent is standard practice for inventors. Secretiveness prior to annoncement of a discovery is also acceptable for scientists, but once the word is out in a pubic forum, then the details necessary for replication are supposed to be accessible. Promoting 'vaporware' is an acceptable strategy for inventors/entrepreneurs like Thomas Edison or Bill Gates, who make extravagant promises they expect they will be able to fulfill eventually. Perhaps Pons and Fleischmann were doing the scientific equivalent of vaporware.
Of course, the amount of detail required for replication is often the subject of intense negotiation (Collins, 1985; Collins & Pinch, 1993) and this controversy was no exception. Laboratories all over the world tried to get details; in some cases, they ran experiments based on photographs from newspapers and television reports. At first, results from Georgia Tech, Texas A&M and the University of Washington appeared to support cold fusion, but as these researchers searched for alternate explanations, they found serious problems that led them to retract their initial positive findings and other laboratories at MIT, Caltech and other locations weighed in with negative results. Furthermore, Pons and Fleischmann's reluctance to collaborate with other scientists and share data led to attacks on their integrity. Had Pons and Fleischmann stuck with a scientific goal, rather than an inventor's, their reputations might have fared better-- they could then have supplied the details that the scientific community wanted. However, this kind of openness would have made it harder for them to profit from this revolutionary new energy source, if it panned out. To put it in simple terms, failure to replicate a discovery is bad; failure to replicate an invention simply means that the original inventor and her partners have a competitive edge--the longer it takes others to replicate, the better. Pons and Fleischmann' lawyers even threatened to sue over a critical article that appeared in Nature; again, the courts are an appropriate forum for sorting out inventors' disputes, but not scientists'.
Edison made a similar mistake with his first announcement of the 'etheric force' (Gorman, 1989). In 1875, while conducting experiments on multiple telegraphy, Edison noticed that when the current to an electromagnet was interrupted, sparks could be drawn off a variety of metal objects in the laboratory. Not only did these sparks emerge at a greater distance than any he had seen before, they appeared to have neither a positive nor a negative charge. He thought he had discovered a new physical force, which he labeled etheric because it seemed to travel through the invisible ether that was supposed to carry light waves. Edison was used to announcing his new inventions to the newspapers, often long in advance of their reduction to practice. He did the same with his new discovery, and a sympathetic New York Herald reporter announced that:
The cumbersome appliances transmitting ordinary electricity, such as telegraph poles, insulating knobs, cable-sheathings may be left out...and a great saving of time and labor accomplished. Ocean cables [may be] operated by "etheric force"...The existing methods or mechanisms may be completely revolutionized (Josephson, 1959, p. 129).
Note that Edison emphasized the potential inventions to the reporter, not the theoretical implications. The scientific community greeted this new force with skepticism, and the future inventor Elihu Thomson played a crucial role in disconfirming Edison's force when he and Edwin Houston showed that it did carry a charge. Edison dropped his pursuit of the etheric force, and left it to Marconi, Tesla and others to explore the phenomenon of radio waves.
Both Pons & Fleischmann and Edison were more concerned about patent priority than scientific credit, so they risked early announcements of discoveries after a few confirmatory tests. Fleischmann's philosophy was "that if you really don't believe something deeply enough before you do an experiment, you will never get it to work" (Taubes, 1993, p. 118). He might also have added that if the researcher does not believe in a phenomenon, she or he will be unable to persuade funding agencies to back it. Moscovici emphasized that a minority view was most likely to prevail when its advocates adopted a consistent behavioral style, arguing persistently for their point of view (Moscovici, 1974). Rosenwein modified this generalization by pointing out that it is a patterned consistency that is most effective; the minority must be responsive to changes in the situation, including new evidence, without abandoning its central point of view (Rosenwein, 1994). This is akin to Lakatos' observation that scientific research programs rarely modify their hard core ideas, but are willing to alter or abandon corollary assumptions *(Lakatos, 1978).
Pons and Fleischmann did show a kind of patterned consistency, arguing persistently for the existence of cold fusion, but taking account of new evidence by re-interpreting it to fit their view. For example, they did not run a light-water control until they had been challenged at a number of conferences and when they did run it, they found out that both heavy and light water cells produced fusion. They treated this result as a great new discovery. They now had a form of fusion that produced virtually no neutrons and worked with regular water as well as with deuterium, but they were ready to rewrite the laws of nuclear physics rather than abandon their hypothesis. In their case, a confirmation heuristic turned into a bias.
A key element of patterned consistency, according to Rosenwein, is 'playing by the rules': remaining within the community of scientists, rather than splitting-off and joining another community. Pons and Fleischmann acted more like inventors. The point in a patent is to be revolutionary, as different as possible from whatever went before (Myers, 1995). Pons and Fleischnmann were certainly revolutionaries, in the classic Kuhnian sense, but they were never able to produce a working model of a cell that consistently generated power and their anomalies were eventually dismissed as errors.
The historian Thomas Hughes has talked about reverse salients in the development of complex technological systems. "A salient is a protrusion in a geometric figure, a line of battle, or an expanding weather front. As technological systems expand, reverse salients develop. Reverse salients are components in the system that have fallen behind or are out of phase with the others" (Hughes, 1987).
Reverse salients attract inventors--solving such a problem is a sure way to fame and fortune. Therefore, reverse salients create the opportunity for multiple simultaneous inventions. The invention of the microchip serves as an example. The reverse salient, in this case, was the problem of the 'tyranny of numbers'. In the late 1950s, a new aircraft carrier "had 350,000 electronic components, requiring millions of hand-soldered connections; the labor cost--for wiring those connections and testing each one--was greater than the total cost of the components themselves. Production of the first 'second generation' (i.e. completely transistorized) computer--the control data CD 1604, containing 25,000 transistors, 100,000 diodes, and hundreds of thousands of resistors and capacitors--lagged hopelessly behind schedule because of the sheer difficulty of connecting the parts" (Reid, 1984).
A solution was arrived at independently by two inventors--Jack Kilby and Robert Noyce, both of whom filed patents for a 'monolithic circuit', in which all the components could be made out of silicon.
Kilby and Noyce arrived at this idea via different routes. Kilby had just gone to work for Texas Instruments (TI), and was assigned to work on a project called the 'MicroModule', a product he was sure would not work. When he arrived at his new job, everyone else was off on vacation, so he tried to come up with an alternative lest he be forced to work on a bad idea. TI was heavily into silicon, so he studied that material carefully and realized, as he said in his notebook on July 24, 1958, "The following circuit elements could be made on a single slice: resistors, capacitor, distributed capacitor, transistor" (Reid, 1984, p. 65). Integrating all these components on a silicon wafer would avoid the need for soldering. He built a prototype; when it worked, TI embraced the idea, and Kilby filed a patent application on February 6, 1959.
Kilby was a quiet, introverted type who preferred working alone. Noyce, on the other hand, was as good at inventing companies as new technologies; he was at that point working for Fairchild Semiconductor, a company he had founded with seven colleagues. He would soon be involved in the creation of Intel. Noyce was one of the engineers who created the archetype of the Silicon Valley entrepreneur. In 1958, Fairchild was making silicon transistors on a single wafer "and then we cut them apart into tiny pieces and had to hire thousands of women with tweezers to pick them up and try to wire them together again...The answer, of course, was don't cut them apart in the first place--but nobody realized that then" (Reid, 1984).
Noyce was in the process of patenting another idea--putting a silicon oxide layer on top of a chip to protect it from contamination--when the patent lawyer kept pushing him to imagine other applications. Noyce realized one could print circuit components right on the oxide layer; first he thought of using copper wire, then silicon. Eventually, six months after Kilby, he had the monolithic circuit and filed a patent on July 30, 1959.
Even though Noyce's application was second, he was the first to get the patent. It is not unusual for one application to be processed faster than another, so Kilby's lawyers filed for an interference proceeding, in which a special Board of Patent Interference tries to determine who invented first. Kilby's notebook entry was six months prior to Noyce's, so he was granted the patent. Then Fairchild's lawyers developed a new tactic--they attacked an unfortunate picture in Kilby's patent application which showed wires sticking out of the chip--not at all what an integrated circuit really looked like. After ten years of dispute, and several reversals, Noyce won the patent battle.
By this time, it was irrelevant--the two companies had settled years earlier, granting each other licenses for integrated circuit production and sharing royalty fees from other companies. Furthermore, Kilby and Noyce happily shared credit as co-inventors.
Most inventors are not so willing to share credit. Indeed, one of the greatest motives behind patent disputes is getting credit for being the first to invent something--the money that comes along with the credit is often secondary in the minds of the inventors, though not in the minds of their backers and companies who rely on licensing their patents.
The dispute over the invention of the radio is a case in point. There were many contenders, but two inventors emerged with stronger claims than the others. Lee de Forest invented and patented a wireless telegraph receiver he called the audion in 1906. He didn't understand how it worked, but work it did. It was Edwin Howard Armstrong who figured that out in 1912, and greatly amplified the sound by feeding the oscillating current back and forth many thousands of times. Armstrong also saw that this receiver could be turned into a transmitter. Unfortunately, Armstrong lacked the $150 necessary to apply for a patent right away and did not do so until 1914, at which point his application was put into interference with one by de Forest. Armstrong was the initial winner, but he refused an opportunity to settle with de Forest, thereby ending further appeals because Armstrong wanted to be known as the sole inventor of the circuit that made radio possible. Eventually, the Armstrong victories were reversed, on the grounds that a notebook sketch by de Forest's assistant made on August 6, 1912, showed a circuit that could have achieved the feedback effect--even though it was clear from the entry that the experiment had failed (Lewis, 1991). Armstrong ended-up battling the mighty Radoi Corporation of America over patent infringement. Heveered close to bankruptcy, and killed himself on January 31, 1954--the forty-year anniversary of the day he and David Sarnff, the future president of RCA, had spent a happy night using Armstrong's powerful receiver to copy telegraph messages from all over the world. It was Armstrong's widow, Marion, who successfully pursued a long series of court cases that resulted in his posthumously being recognized as the inventor of FM.
No businessman would have invented the telephone. It's got to be a maverick--some guy who's been working with the deaf and gets the crazy idea that you could actually send the human voice over a wire...A businessman would have been out taking a market survey, and since it was a nonexistent product, he would have proven conclusively that the market for a telephone was zero. (Reid, 1984, p. 70).
If Gray had filed an application for a patent and Bell for a caveat, we should in all probability have today the Gray Telephone Company in place of the Bell Telephone Company. *(Lloyd Taylor, IV, p. 6)
Alexander Graham Bell was eventually upheld as the inventor of the telephone, but only after years of litigation with rivals, including Elisha Gray, Daniel Drawbaugh and many others. The controversy with Gray was especially bitter, because on the day Bell submitted a patent application for a device that could, among other things, transmit speech, Gray submitted a caveat for a device that would serve the same function. (A caveat was a statement of intention to perfect and eventually patent an invention--it was filed with the patent office and could be used to establish an inventor's priority). Indeed, Gray practically accused Bell of stealing his idea: "And, notwithstanding there were suspicious circumstances early in the history of the telephone, it was not until eight or ten years--at least, a long time after the telephone was in use--that I became convinced, chiefly through Bell's own testimony in various suits, that I had showed him how to construct the telephone with which he obtained his first results" (Taylor, Unpublished Manuscript, IX, p. 6).
Basically, there are three possibilities:
1) Gray was the original inventor of what we now call the telephone; Bell simply borrowed his ideas.
2) Gray and Bell arrived independently at the idea for what we now call the telephone, in which case Gray deserves equal billing as inventor.
3) It is only hindsight that makes it appear as though Gray and Bell were inventing the same thing. The case of radio is instructive, here. The courts eventually concluded that de Forest had invented the same regenerative circuit as Armstrong, even though de Forest didn't understand how it operated and his only experiment with it failed. Simply put, de Forest and Armstrong's devices were embodiments of different mental models--they were not viewed in the same way by the inventors, and only hindsight has made them appear to be the same.
In the mid 1870s, one of the reverse salients lay in the area of multiple telegraphy. The telegraph had transformed the world. Messages could now be sent over great distances, much faster than any human messenger could have carried them and almost regardless of weather conditions. The importance of the telegraph was illustrated in the American civil war; Lincoln spent much of his time at the telegraph office, communicating with his generals and assessing reports from the field. Both sides tapped and cut each others telegraph lines.
The telegraph transformed commerce as well as war. Stock quotes could be sent from New York to Chicago with great rapidity. The result was that many of America's large cities were festooned with uninsulated wires from telegraphs, utilities and burglar alarms, which could become crisscrossed and tangled, creating dangerous shorts which interrupted communications. The wires were expensive to install and maintain. This created a reverse salient. If a way could be found to send multiple messages over a single wire, it would eliminate the salient. This was the problem that attracted Gray, Bell, Edison and a host of other inventors.
But while several inventors may be working on the same reverse salient, there is no guarantee that they view the problem in the same way--or even identify the salient as the same problem. In order to understand the way each inventor views a problem such as the transmission of multiple messages, we will use the framework outlined in previous chapters. To refresh the reader's memory, we will use Edison's kinetoscope as an example.
(1) Mental models:
In developing his kinetoscope, or motion picture camera, Edison's goal was to do "for the eye what the phonograph does for the ear, which is the recording and reproduction of things in motion, and in such a form as to be both cheap, practical and convenient [by] photographing continuously a series of pictures occurring at intervals... in a continuous spiral on a cylinder or plate in the same manner as sound is recorded on a phonograph." (Josephson, 1959). Indeed, he intended to put his kinetoscope cylinder on the same shaft with a phonograph cylinder, in order to coordinate sound and pictures.
Now in what sense is this rough idea of Edison's a mental model? He could run alternatives for this system in his 'mind's eye', imagining how it might work. To select among alternatives and turn imagination into reality, Edison needed to rely on:
(2) Mechanical Representations:
Robert Fulton, inventor of the steamboat, argued that "the mechanic should sit down among levers, screws, wedges, wheels, etc. like a poet among the letters of the alphabet, considering them as the exhibition of his thoughts; in which a new arrangement transmits a new idea to the world" (Gorman, 1992, p. 47). If we substitute inventor for mechanic, and include the possibility that an inventor can transform the standard 'levers, screws, and wedges' into devices suited to her class of problems, then Fulton's quote contains the idea of a mechanical representation--a familiar component that an inventor can use repeatedly to create new designs. As Reese Jenkins noted, "Any creative technologist possesses a mental set of stock solutions from which he draws in addressing problems" (Jenkins, 1984, p. 153).
The drum cylinder Edison used in both the phonograph and the kinetoscope serves as an example: it became for Edison a standard solution to the problem of creating a smooth, continuous rotation. To interrupt this rotation to allow pictures to be shown in his kinetoscope, he used another mechanical representation: a double-acting pawl he had developed for use in stock tickers (Carlson, 1990).
The difference between a mental model and a mechanical representation is that the former is incomplete and represents a possible path to a solution, whereas the latter is embodied in a completed device that represents a solution to part of a problem. Why refer to this sort of a device as a representation? Because not all aspects of the solution embodied in the device are recoverable simply by studying the device--one also must know how the device is represented by the user (Norman, 1983).
Inventors can plug these mechanical representations into their mental models, thereby using a lower-level representation that is embodied in a device to fill in a higher level model. Several years ago I attended an extraordinary conference on invention organized by Robert Weber and David Perkins (Weber & Perkins, 1992), and I am indebted to them for drawing my attention to the idea of slots.
For Weber and Perkins, the fundamental representation is a frame:
An entity with slots in which particular values, relations, procedures, or even other frames reside; as such, the frame is a framework or skeletal structure with places in which to put things. The slot is a generalization of the idea of a variable. The frame then represents an object, event, or concept in which the slots are the defining characteristics; the values of the slots are the instantiations of the variables, attributes, relations or procedures. (Weber & Perkins, 1989)
The idea of a frame was developed as a way of translating representations into a computational form. A simple example of a frame is a tax form, which has slots like 'name' and 'number of dependents', each of which can contain different values, e.g., 'Sue Smith' and '2'. A more complex example would be a frame for dog. This frame would inherit some characteristics from the overall frame for mammal, including certain slots and values. For example, we might include a slot for 'means of propagation'. Under mammal, that means would be 'live birth'. As an instance of mammal, dog would inherit that slot and value. Dog would also have some unique slots. We might include a slot for 'type of breed', which would include values like spaniel or retriever; within each type of breed, there might be slots for particular breeds like Springer Spaniel or Golden Retriever. This example illustrates the flexibility of the notion of a frame; it gives us lots of room for creating different slots.
A mental model can be viewed as a kind of frame, but one that is more visual and kinesthetic than other more prepositional types of frames. Dog, for example, is more than an abstract concept; most of us have a visual mental model of a dog, perhaps based on our favorite dog. Depending on our individual mental models, certain breeds may look less 'dog-like' to some of us (Rosch, 1973). (A friend of mine was walking his deerhound one day, and a stranger asked if it was a goat or a llama).
Frames can be nested within frames. Similarly, mental models can be nested within mental models. An inventor can have a mental model of an overall system, and also a mental model of how a part of a system might work.
Like frames, one could imagine mental models being divided into slots. For example, Edison's mental model for a kinetoscope included a slot for a mechanism by which the pictures would be advanced continuously. Edison filled this slot with the drum cylinder from the phonograph.
Substituting different mechanical representations can lead to a transformation in the overall mental model. Edison's capable assistant William Dickson substituted a different mechanical representation for the drum cylinder; he used a tachyscope, a rapidly rotating wheel on which pictures could be mounted. Dickson managed to project these moving images on a screen and coordinate them with a phonograph so when Edison returned from a trip in March of 1890, he was greeted by a moving image of Dickson, raising his hat and saying, "Good morning, Mr. Edison, glad to see you back, I hope you are satisfied with the kinetophonograph." (Carlson and Gorman, 1990, p. 107).
Instead of embracing this solution, Edison ordered Dickson to abandon it. Dickson's adoption of a new mechanical representation had forced a change in the overall mental model guiding the development of the system. It was no longer a 'phonograph for the eyes', intended--like the early phonographs--for use in an individual viewing booth.
The Edison/Dickson example illustrates one of the ways in which mental models can become evident--when an inventor resists an alternate design. This kind of 'mental inertia' corresponds to the kind of 'confirmation bias' found in the early experimental simulations of scientific reasoning. In the last chapter, we noted that more recent research has focused on the advantages of confirmation. As Tweney & Chitwood point out, "In contrast to the usual focus on confirmation bias as a reflection of the limits of human cognition, the evidence suggests that a confirmation heuristic is one of the highly functional means by which knowledge is made possible" (Tweney & Chitwood, 1995, p. 235).
(3) Heuristics:
David Perkins (Perkins, 1997) uses the metaphor of wilderness to describe the search for a solution to an invention problem. In Perkins' view, the inventor's goal should be to transform a Klondike space, in which the inventor knows there is gold somewhere in the wilderness but is not sure where, into a homing space, in which the inventor knows the goal is near. Heuristics are rules of thumb for making this transformation. Just as the gold prospector might use some rough rules for deciding where to pan, so the inventor can apply heuristics like 'see if nature has solved a similar problem and if so, imitate nature'. The first inventions were modifications of natural objects (Basalla, 1988); current inventions are more likely to be based on an analogy to nature. Velcro, for example, was based on such an analogy; George de Mestral used a microsope to study the way in which burrs attached to his clothing, and noted the collection of miniature hooks and eyes. It took about ten years to translate this mental model into a product.
The problem with the wilderness metaphor is that it suggests all the inventor's gold is 'out there', waiting to be discovered. In fact, inventors are in the business of creating new kinds of substances and convincing the rest of us that they are precious (Ward, Finke, & Smith, 1995).
However, if not taken too literally, the metaphor is helpful. There are general heuristics that can be used across a wide range of problems, in order to create homing spaces--like looking for an analogy in nature, and following it. There are also domain-specific heuristics that are useful in homing spaces within well-defined domains. Sociologist of science Harry Collins provides several good examples, including "In crystal growing always start the melt cooling from well above the putative melting point", and "The tolerance of TEA-laser electrodes are sufficiently large to make it unlikely that the exact shape of the electrodes is the cause of failure" (Collins, 1990, p. 108) . Hans Krebs learned a set of heuristics like tissue-slicing from his first mentor on laboratory methods, Otto Warburg (Holmes, 1991, p. 295).
These domain-specific heuristics can be transformed by a particular scientist or engineer into individual heuristics. This is particularly likely to happen with inventors and discoverers, whose work frequently takes them beyond the bounds of existing techniques. At one critical point in his researches on ornithine, Hans Krebs had to modify the tissue-slicing heuristic he had learned from Otto Warburg by developing a new heuristic for determining the best medium in which to bathe the slices while they were being tested. Basically, he used a general heuristic--when in doubt, look at nature's solution to a similar problem--and decided to "imitate as closely as possible the actual physiological situation in which tissues normally exist" by duplicating the composition of plasma as closely as possible (Holmes, 1991). Krebs used a weak or general heuristic to develop his own strong heuristic. Alexander Graham Bell used the same weak heuristic, which he called "follow the analogy of nature," to develop a powerful mental model for creating a device that could transmit speech.
Heuristics, like mental models, often become apparent when a kind of resistance is encountered--a resistance that forces the problem-solver to articulate and defend her approach. For example, an expert who solves a certain class of problems automatically, without thinking, may have to struggle to describe her heuristics when queried by a novice. This fact has led Suchman and others to argue that heuristics, like plans, may be post-hoc rationalizations invented by problem-solvers to explain what they do (Suchman, 1987).
I had a calculus professor in college who, in the days before hand-held calculators and desktop computers, would put a long integral on the board and solve it in seconds. He had worked in industry and had developed a powerful set of domain-specific heuristics which he had trouble explaining. I had to get another math professor to work with him and explain his tacit knowledge to me. This example illustrates that heuristics do not always have to be post-hoc rationalizations.
Taken together, heuristics, mental models and mechanical representations allow us to study and compare the cognitive styles of inventors and discoverers, by which I mean the manner in which each individual practitioner finds, transforms and solves problems.
To investigate general heuristics and representations, we need multiple case studies of inventors and discoverers working in different domains. To investigate domain-specific heuristics and the sorts of mental models and mechanical representations that are shared by experts, we need to add multiple case-studies within an area of expertise. Inventors and discoverers, however, are continually stretching beyond recognized domains, reconfiguring the landscape of expertise; to investigate this process of problem transformation, we need to add comparisons of different inventors and discoverers working on what in hindsight came to be regarded as the same problem.
Hence, we will spend a good portion of the rest of the chapter on a fine-grained comparison of two men, each of whom claimed to have been inventor of the telephone. In addition to the three categories above, we will need also to talk about themes, goals and plans (Schank & Abelson, 1977). Themes correspond to the very general goals people adopt, e.g., make tons of money or be creative, and also the roles they adopt to achieve them, e.g., entrepreneur or painter. Unlike generals and entrepreneurs, inventors rarely talk about goals and plans--they simply design, and often one must infer their intentions from their design processes.
Initially, both Bell and Elisha Gray focused on harmonic telegraphy: the idea of using multiple tones, singly or in combination, to send multiple messages down the same wire. For Bell, this goal emerged from one of his themes. Bell's family was very involved with teaching the deaf. His father, Alexander Melville, developed a special 'visual speech' alphabet which deaf people could use to read how to make specific sounds. As a boy, Bell would participate in demonstrations in which he was placed out of earshot; his father would ask a member of the audience to make a sound, then he would write it in visible speech; Bell would enter, read what his father had written, and make the sound. So Bell inherited a family theme, or mission, having to do with teaching the deaf and making speech visible to the deaf.
Gray's themes are harder to reconstruct than Bell's, because Gray left less in the way of written records and the only biography, by Lloyd Taylor, is an unpublished work of uneven quality (Taylor, Unpublished Manuscript). Elisha Gray was born in Barnesville, Ohio in 1835. He magnaged to build a working model of Morse's telegraph before he was ten, but the death of his father and his mother's precarious health made Elisha the primary breadwinner in the family at the age of 12. He took up carpentry until he could enroll as a student at Oberlin College, where he encountered a mentor in the form of his science teacher, Charles Churchill, who inspred Gray's continued interest in electronics and telegraph , (Hounshell, 1975). Here the themes of hard work and telegraph invention seem to join, though we know very little about this period in Gray's life.
Like Bell, Gray often overworked to the point of illness--he managed to put himself through five years of Oberlin but paid with five years of convalescence (Hounshell, 1975). He gained much of his knowledge through his hands: "While studying natural philosophy, it was my custom to make and carry with me into the class such apparatus as could be readily constructed and would serve to illustrate the lesson. My habit of actually constructing everything which I saw or read of so far as my facilities would allow, was the best possible method of fixing the principles of its operation firmly in my mind" (Gray, 1977, p. 6).
His electrical researches paid off in 1867, when he developed a new form of telegraph relay. He formed a partnership with Enos Barton in 1869; they founded the Western Electric Company, which became. the major manufacturer of telegraph equipment for Western Union. Bell's father introduced Alec to the scientific community; Gray's hard struggle for survival inclined him more to the world of business.
Each inventor suspected the other of stealing his ideas at various points. Gray submitted a patent application for a multiple harmonic telegraph on February 23, 1875; two days later Bell submitted one for his. These closely timed submissions foreshadow the competition over the telephone, in which Gray filed a caveat on the same day Bell filed a patent. (A caveat was a document that could be filed with the patent office to signal an inventor's intention to submit a patent at a future date, when her invention was closer to realization).
So the famous controversy between Bell and Gray over the speaking telegraph, or what we now call the telephone , was really one episode in a continuing controversy over multiple telegraphy. In the telegraphy controversy, we will focus on the way in which Gray and Bell evolved similar mechanical representations for receivers; in the telephone, we will show how they evolved similar transmitters. In both cases, however, there were important differences in how each inventor viewed the function of devices that appear similar on the benchtop. An invention that looks the same in hindsight was not always viewed as the same by the inventors at the time.
Gray later claimed he got the first idea for using musical tones to send telegraph messages in 1867, when he was using a vibrating metal reed, or rheotome, in a circuit with an electromagnet and a telegraph key. When he closed the key, he "noticed a singing sound in the electro-magnet, and by working the [telegraph] key as if transmitting a Morse message, the signals were audibly produced on the magnet by long and short sounds, representing the dots and dashes of the Morse alphabet" (Gray, 1977). Gray makes this sound like an entirely serendipitous experimental result, but by this time, he probably had heard of--and even seen demonstrated--the first telephone, constructed by Philip Reis in Germany in 1854. This device was designed to transmit musical tones. The transmitter consisted of a lever with a point, which rested on a membrane; when one sung a note, the membrane would cause the lever bounce, alternately making and breaking contact with a piece of platinum in the middle of the membrane. This intermittent, on-off current would alternately magnetize and de-magnetize a receiving electromagnet, which would reproduce whatever tone had been sung into the membrane. The Reis apparatus was widely known at the time (1880). Gray later referred to his musical telegraph devices as telephones. Unlike Bell, Gray did not document his sources; therefore, it is hard to be sure where his background knowledge came from.
Gray's next mental model for a harmonic telegraph came from observing his nephew touching a zinc-lined bathtub with one hand while in the other he held a coil connected to a vibrating rheotome, an electromagnetic device which produced a tone. When his nephew's hand glided along the zinc, Gray heard the bathtub emit the same tone as the rheotome. When Gray put himself in his nephew's position, he found he could alther the pitch and volume by changing the speed and pressure with which he rubbed the zinc.
It was Pasteur who said that chance favors the prepared mind. In this case, a child's game provided Gray with a mental model for a musical telegraph. A single telegraph receiver could potentially reproduce multiple tones. He was so excited by the potential of this discovery that he resigned as superintendent of Western Electric to pursue his inventions full time.
In April of 1874 Gray attempted to patent a musical telegraph, which consisted of a two-tone transmitter, consisting of two single-pole electromagnets, each with a vibrating armature. Each armature made and broke contact with a platinum point which switched the current on and off to the coil. Because each electromagnet had a different electrical resistance, each electromagnet exerted a different magnetic pull on its armature and thus caused each armature to vibrate at a different frequency. Each coil and armature combination was controlled by its own telegraph key, so that each frequency could be sent separately or simultaneously. These electromagnets were connected to an induction coil which functioned like a modern transformer and stepped up the current before it was sent out onto the telegraph line. For the zinc bathtub, Gray substituted a grounded piece of galvanized tin. The patent drawing shows a man--presumably Gray himself--holding the wire from the coil in one hand and touching the tin with the other (see Figure 9 from Gray's patent 166,096). The transmitter sent two different, audible tones which were reproduced on the tin plate receiver as the man rubbed it.
Figure 9: Drawing of Elisha Gray in a circuit from his Animal Tissue Patent 166,096. In this case, Gray himself was the animal tissue. In later patents, he substituted other materials.
The patent office initially rejected this application, on the grounds that one could not patent a circuit which included a person. So Gray converted the person into a slot into which he could substitute a variety of animal tissues, ranging from oyster shell to leather. He was eventually granted a patent in February of 1876.
By then, Gray had moved on. He expanded his two-tone transmitter to a two-octave device that could send twenty-four different pitches (two octaves) over one telegraphic circuit. Each tone was generated by a single tone transmitter tuned to a different pitch. Gray often used several single tone transmitters inside more complex devices capable of sending multiple tones, such as his two octave transmitter and printing telegraph. Because he used the single tone transmitter by inserting it into slots in different inventions, it became one of Gray's mechanical representations.
Gray also developed several receivers to take the place of the awkward animal tissue combination. His mental model was the telephone receiver developed by Philip Reis. According to Gray, the principle of the Reis receiver was that 'when a coil of wire surrounding a bar of iron or the core of an electromagnet is traversed by an electric current, the said bar will be slightly elongated, and if these currents succeed each other with sufficient rapidity, a vibratory motion will be given to said bar, and it will give forth a musical tone.'
All of Gray's receivers embodied this principle and hence were capable of reproducing several tones simultaneously, but they employed different mechanical representations in the amplification of the vibrating core of the electromagnets. So while the Reis receiver functioned as Gray's receiver mental model, these mechanical representations came from several other sources. For example, he used a variety of resonant cavities to amplify the sound. He got the idea of using a tin drum from a combination of the tin he used in his animal tissue patents and experiments with a violin with a metal plate on the back. His previous experience with using a bathtub as a receiver led him to substitute a wash basin.
He systematically tested every type of receiver with his two-octave transmitter With these instruments Gray gave several impressive demonstrations in New York and Washington in May and June, 1874, after which he returned home to Chicago.
Gray claimed that, upon returning to Chicago, he worked on the problem of creating a reliable harmonic telegraph transmitter. His two-octave transmitter could theoretically have been used for such a purpose, but Gray apparently thought it more suited to sending composite tones than isolated individual messages. His solution to the transmitter problem was to use "an ordinary electro-magnet and a reed made of a piece of watch-spring, one end of which is fixed to one pole of the magnet while the other free end projects over the other pole, a short distance from it, so as to form an armature" (Gray, 1977, pp. 21-2). Each of these springs could be tuned to a particular frequency. These springs produced an excellent tone for a short time, "but the slightest change in the adjustment, even a jar of the table, causes it to break into nodes, and give a note a chord or an octave away from its fundamental" (Gray, 1977, p. 23). At this point, I want to turn back to Bell, who evolved a device that looked very similar to Gray's reed transmitter, foreshadowing the later conflict between the inventors over the telephone.
When Elisha Gray began his multiple telegraph work, he was already an accomplished electrical inventor. Bell's area of expertise, by contrast, was speech and audition. In 1863, his father, Alexander Melville, had challenged Alec and his older brother Melly to manufacture an artificial mouth and nasal passage, complete with vocal chords. The inspiration was Wheatstone's version of an 18th century device for imitating the human voice. The boys eventually succeeded in making the device say "mama" so realistically that a tenant came down to see what was the matter with the baby (Bruce, 1973, p. 37). Bell learned a great deal about how consonants and vowels are formed from this exercise, and it also taught him the value of using a heuristic he would later call 'follow the analogy of nature'.
Like Elisha Gray, much of Bell's knowledge came through building and tinkering, but Bell was gaining expertise in speech, rather than electricity. In another set of experiments, he discovered that he could hold a vibrating tuning fork in front of his mouth and while moving his tongue through the positions of the vowels, one of the vowel positions would cause the fork to resonate. He experimented with combinations of tuning forks and vowels, making what he thought were important discoveries. But when he sent a letter to Alexander Ellis, the great phonetician, he learned that he had been replicating experiments conducted by Hermann von Helmholtz. He derived some comfort from the fact that he had followed in the footsteps of one of the world's greatest scientists.
Bell's first idea for a multiple telegraph came from a conversation with Ellis about Helmholtz's apparatus for artificially producing vowel tones, by means of combinations of tuning forks and resonant chambers. Ellis had to do some translating from the German for Bell, and as a result, Bell got the false impression that the device transmitted vowel sounds, when in fact it created them. If vowels could be transmitted, why not consonants and, eventually, speech?
Here we begin to see one of the distinctions between discoverer and inventor. Helmholtz invented apparatus in order to develop and test hypotheses; he was not concerned about commercial applications. Bell, on the other hand, was looking for a way to achieve financial independence, and transformed Helmholtz's apparatus into a mental model of how speech and tones might be transmitted over a wire.
Bell's initial focus was not on speech but on the reverse salient. Why not take two forks that produced exactly the same tone and turn one into a telegraph transmitter and the other into a receiver? If one could do this with one pair of forks, why not do it with four, eight or even sixteen distinct tones, all carrying information down the same wire?
Like Edison, Bell read everything he could get his hands on that was related to his invention ideas. From J. Baille's The Wonders of Electricity Bell got the idea of substituting a steel plate for a tuning fork. Books like Baille's served almost as catalogues of possible electro-mechanical variations for inventors; like Gray, Bell found he had to transform existing components into mechanical representations he could work with. Figure 10 shows several of the stages in the evolution of Bell's steel reed transceiver. The result was a steel reed device whose pitch could be precisely tuned simply by adjusting the length of it that was allowed to hang over the electromagnet. I call Bell's device a 'transceiver' because Bell intended to use the same as both transmitter and receiver.
Figure 10: Three stages in the evolution of Bell's reed mechanical representation, starting with tuning forks at the top, then switching to a steel reed in a sounding, and finally an adjustable reed over the poles of an electromagnet. He also employed a design in which the reed vibrated over the single pole of an electromagnet . His work in this area was influenced by sources like Baille's Wonders of Electricity ((Baille, 1872).
Bell had great difficulty putting these reed relays into an effective multiple telegraph circuit, which led him to develop a new theme, or role, for himself in November of 1873, when he wrote, "It became evident to me, that with my own crude workmanship, and with the limited time and means at my disposal, I could not hope to construct any better models. I therefore from this time devoted less time to practical experiment than to the theoretical development of the details of the invention" *(Bell, 1876, p. 8).
Gray, in contrast, was a master at constructing complex circuits. But in this account, we will focus on how he developed a mechanical representation that bears a resemblance to Bell's. Figure 11 shows the evolution of Gray's reed mechanical representation. In order to make his reed assemblage better able to transmit single tones, Gray made the spring into a heavier metal reed, filed the end of the reed to tune it, and added a small spring to dampen its vibrations. For a single-tone or analyzing receiver, he first tried a tuning fork attached to one pole of an electromagnet. Then he substituted a spring or lever for the fork. Next, he tried a steel ribbon clamped on both ends: "The length and size of the ribbon depend upon the note we wish to receive upon it. If it is a high note, we make it thinner and shorter; if it is a low note, we make it thicker and longer. If this ribbon is tuned to that it will give a certain note when made to vibrate mechanically, and the note which corresponds to its fundamental is then transmitted through its magnet, it will respond and vibrate in unison with its transmitted note; but if another note be sent which varies at all from its fundamental, it will not respond. If a composite tone is sent, the ribbon will respond when its own note is being sent as part of the composite tone, but as soon as its own tone is left out it will immediately stop. This I am able to select out and indicate when any note is being sent, in fact, to analyze the tones which are passing over the line" (Ashley, October 21, 1876).
Figure 11: The evolution of Gray's reed mechanical representations. Note the way in which Gray appears to operate in separate transmitter and receiver slots, ending up with different mechanical representations for each.
Unlike Bell, Gray was not working to get a single preferred mechanical representation. He had specific ways of configuring his reed when it was to serve as a transmitter and as a receiver. This difference in function between Bell's and Gray's apparently similar devices illustrates why I use the term mechanical representation. Bell and Gray saw different possibilities in their reed devices.
Gray wanted to patent a variety of transmitters and receivers that could be used in combination. Therefore, Figure 11* is somewhat misleading--it shows that Gray could work incrementally to improve his transmitters and receivers, but does not show all the other variations he was generating at a similar time. Gray's cognitive style could be best described by a matrix: he developed a set of alternate mechanical representations for transmitters and receivers, and tested and patented many of the possible combinations. In Gray's case, substitution of mechanical representations in different slots did not lead to radical changes in his overall mental model of how a multiple harmonic telegraph might work; instead, it gave him more variations to experiment with as he tried to reduce his ideas to practice.
Bell's first mental model for a speaking telegraph came from a variation on this reed mechanical representation, and also from experiments he had conducted with piano strings. In the summer of 1874, he put reeds on either pole of a horseshoe magnet, and experimented with sending the sound of either reed, separately or in combination. Bell's goal was to magnetize the reed itself and therefore avoid distortions that occurred when he used an unmagnetized reed in combination with an electromagnet--exactly the sorts of distortions that Gray was able to avoid through clever use of dampers and electromagnets of different resistances.
Bell's horseshoe magnet experiment was partly successful, enough to lead him to imagine a device he called the 'harp apparatus' with perhaps dozens of reeds on each pole of an electromagnet (see Figure 12). Such a device might function like the strings on a piano and vibrate in response to any tone made near them; these vibrations would then induce a current which could be carried to a receiving harp.
This harp was never built, and it was not fully described even in the sketch shown in Figure 12; instead, it served as a mental model--incomplete and unstable, because Bell had no idea how many reeds it would take to make it work, and he was sure it would not induce enough current to transmit a signal strong enough to be heard.
Figure 12: Bell's harp apparatus. One would speak against the reeds H, attached to a permanent magnet M; the vibration of the reeds would induce a curret in the electromagnet E which would be transmitted to E', cusing the reeds H' to reproduce the sound. This device was never built; Bell was not even sure how many reeds would be necessary (from Rhodes, 1929, p. 11).
In June of 1875, Bell and his new assistant Thomas Watson were working on the problem of multiple telegraphy. Bell had obtained support from Gardiner Hubbard, father of one of his pupils, Mabel. Hubbard wanted to break Western Union's virtual monopoly on what we would now call information services. He proposed a plan that would put such services in the post office, under contract to a corporation that Hubbard himself would found and head. When the Congress did not pass his scheme, Hubbard looked for other ways of ending Western Union's dominance (Carlson, 1994). One way was through the development of new technologies like the multiple harmonic telegraph system proposed by his daughter's teacher.
To complicate matters, Bell was courting Mabel. Therefore, out of deference to Gardiner Hubbard, telephonic researches had to take a back seat to telegraphy. On May 2nd, 1875, Bell wrote to "Papa and Mama: I think that the transmission of the human voice is much more nearly at hand than I had supposed. However this is kept in the background just now--as every effort is made to complete the Autograph arrangement so as to have it used on some line." The autograph was a device that would sent printed or written letters over a wire, and Bell had just obtained an important patent for this kind of technology, barely beating Elisha Gray.
There may also be a cognitive reason why Bell kept the speaking telegraph in the background, at least for a bit. When a scientist or inventor is pursuing a network of related enterprises, she or he may suspend a goal when confronted with an obstacle, and pursue other, related goals until a solution to the first goal emerges. The problem with the harp apparatus was that it required to many reads and the induced current would not be sufficiently strong to transmit speech. So Bell suspended the goal of speaking telegraphy, hoping a solution would emerge.
This is the beauty of a network of related pursuits--in the course of pursuing telegraphy, Bell found the solution to telephony. On June 2, 1875, Bell had set up three multiple telegraph stations, A, B and C, each with three of his tuned reed mechanical representations. He wanted to be able to pluck the first reed in A and have the first reeds in B & C vibrate. When Bell depressed the telegraph key corresponding to first reed at A, the corresponding reed at B vibrated well, but Watson, who was in another room with C, noticed it was stuck. To release it, Watson plucked it; Bell noticed that this caused the corresponding reed at B to vibrate powerfully. Bell then listened to each of the reeds at B in succession, placing his ear right against them, and heard both the pitch and the overtones of the tuned reed.
Seen from the standpoint of multiple telegraphy, this result was an error--one stuck reed caused three reeds at the other station to vibrate, and one could hear the overtones of each reed, whereas what one really wanted was to hear a single, pure tone. But given Bell's harp mental model, this error suggested a route to the transmission of speech. "These experiments at once removed the doubt that had been in my mind since the summer of 1874, that magneto-electric currents generated by the vibration of an armature in front of an electro-magnet would be too feeble to produce audible effects that could be practically utilized for the purposes of multiple telegraphy and of speech-transmission" (Bell, 1908, p. 59).
Bell immediately asked Watson to build a working telephone in which a reed relay was attached to a diaphragm or membrane with a speaking cavity over it. As one spoke into the cavity, the membrane would vibrate; these vibrations would be translated into an electrical current by the dampened reed, which would send them to a similar device on the other end. Unfortunately, this device did not produce intelligible speech, though Bell and Watson heard a kind of mumbling that suggested they were on the right track. Bell then wrote an application for a patent that included the transmission of speech; he used his reed relays to illustrate how this was to be done. The patent was submitted on February 14th, 1876.
Edison's famous patent for a carbon filament light also may have benefited from a lot of serendipity. By October of 1879, Edison had succeeded in creating a vacuum to one-millionth of an atmosphere in a bulb, had perfected a generator for the lighting system and was experimenting with platinum filaments (Friedel, 1985). The platinum was not entirely satisfactory. Legend has it that Edison was rolling a piece of compressed lambpack between his fingers one night when it occurred to him to put it in his new high vacuum bulb. Previous work had suggested carbon would simply burn up in a lamp, but in the high vacuum, it showed promise.
By June 2nd, 1875, Bell knew most of what he needed to know to create a telephone, but he believed that a single reed could not transmit with sufficient volume. Similarly, most of the pieces of Edison's incandescent lighting system were in place by October of 1877, but he believed that platinum was superior to carbon as a filament. When both inventors encountered results that suggested they were wrong, they were primed to take advantage of them, and went to patent shortly afterwards. In the case of Edison's team, it took several weeks of careful experimenting before they were ready, but even so, it is unlikely that they had a working lamp when they submitted their patent: "The patent application submitted November 4 did not so much describe what had actually been made at Menlo Park as what Edison and his colleagues knew should be made" (Friedel, 1985, p. 106).
A few hours later on the same day, Elisha Gray submitted his caveat for a speaking telegraph. His mental model for the transmission of speech was based on a device called 'the lover's telegraph', or what we would now call a 'string telephone'. According to Gray, this device "proved to my mind that all the conditions necessary for the transmission of an articulate word were contained in any single vibrating point... I saw that if I could reproduce electrically the same motions that were made mechanically at the center of the diaphragm... such electrical vibrations would be reproduced on a common receiver in the same manner that musical tones were" (1880, part II, 124-5).
In his caveat, Gray designed a speaking telegraph that looked like a lover's telegraph with a cylinder of water between transmitter and receiver (see Figure 13). Gray intended to use water as a medium of high resistance. Hanging from the bottom of the speaking tube and diaphragm into which one spoke was a thin wire or rod. When one spoke into the resonant cavity, the diaphragm vibrated, causing the wire hanging from it to get alternately closer to, and farther away from, a contact on the bottom of the water; this motion caused a fluctuation in the current passing to the receiver that mirrored the movement of the diaphragm. The idea of using liquid variable resistance, Gray claimed, was 'old in the art at the time' (1880).
Figure 13: Gray's caveat for a speaking telegraph. The man with the moustache speaks into A, causing the needle attached to the membrane below A to vibrate, going alternately deeper and less deeply into the water at B. At the bottom of B is one end of the circuit; the other is attached to the needle. The water serves as a resistance medium; it conducts electricity, but poorly enough so that the small motion of the needle makes a big difference in the amount of current that flows across the ends of the circuit. The electricity continues to the receiver , which consists of a resonant chamber F and an electromagnet). As the current fluctuates, the strength with which the magnet pulls the bottom of the resonance chamber also fluctuates, causing it to resonate in a manner similar to the numan voice (from Prescott, 1884, p. 455).
Gray used familiar mechanical representations in constructing his speaking telegraph. For example, his receiver consisted of a resonant cavity he had used to receive single tones and a double pole electromagnet he had used in an analyzing receiver.
Because he did not have a working device, Gray filed a caveat or preliminary disclosure instead of a full application, and he was not especially concerned if some details of the apparatus were left somewhat vague. For example, in his caveat, Gray raised the possibility of employing multiple diaphragms just as he had used multiple transmitters in his harmonic telegraphs: "I contemplate, however, the use of a series of diaphragms in a common vocalizing chamber, each diaphragm carrying an independent rod, and responding to a vibration of different rapidity and intensity, in which case contact points mounted on other diaphragms may be employed" (Gray, 1977, p. 79).
In his technical history of the telephone, J.E. Kingsbury cited Gray's preference for multiple chambers to argue that in 1876 Gray was only at the level of understanding that Bell reached with his harp apparatus in 1874, in that each of these diaphragms would function like one of Bell's reeds and it would take a large number of them to reproduce the human voice (Kingsbury, 1915). But as we have seen, Gray's mental model was the lover's telegraph, which did not require multiple diaphragms.
Furthermore, in 1875 Gray had developed a mechanical transmitter with which "we obtained a great variety of sounds on the receiver, not unlike the human voice, imitations of vowel sounds, and also imitations of a groan as if in distress...This experiment with the mechanical transmitter confirmed what my previous experiments had led me to believe: that not only could the receivers that had been named be used as receivers of articulate speech transmitted electrically, but that such speech could be transmitted through a single point. I mean by single point, without the intervention of a series of reeds or points differently tuned, and one that would be a common or universal transmitter, in the same sense that the receivers were universal or common" (1880, p. 124).
So it is not clear why Gray still thought he might have needed multiple diaphragms to transmit speech. Recall Holmes' observation that "in moving from an existing conceptual framework to a new one, scientists often cannot make a single leap from one coherent mental framework to another. They may have to endure, for extended periods of time, deep fissures within their mental worlds" (Holmes, 1989). Similarly, an inventor may simultaneously consider alternate mental models which contradict one another in important respects. Gray's caveat is largely consistent with a mental model for the transmission of speech based on the lover's telegraph, but his remark about multiple transmitters is more consistent with a mental model derived from his musical telegraph experiences, where composite tones were produced by combining single-tone transmitters. Similarly, each of the multiple diaphragms in Gray's speaking telegraph would respond "to a vibration of different rapidity and intensity".
Mental models are provocatively incomplete, often fuzzy in important details. That fuzziness is the key to their creativity--it allows them to contain contradictions that spur the inventor to resolve them.
On June 30, 1875, Bell wrote a triumphant letter to Hubbard: "I shall have ready tomorrow afternoon an instrument modeled after the human ear--by means of which I hope...to transmit a vocal sound...I am like a man in a fog who is sure of his latitude and longitude. I know I am close to the land for which I am bound and when the fog lifts I shall see it right before me." The instrument was a second version of the Gallows telephone, constructed by Watson; it worked little better than the first, but Bell wrote his patent anyway. His reference to 'an instrument modeled after the human ear' can be understood only by looking closely at another line of research in Bell's network of enterprises.
Bell's interest in teaching the deaf kindled his interest in devices used to visualize sound. At the Institute of Technology, he had experimented with the manometric flame capsule, a device that had a speaking tube and membrane on the other side of which was a chamber through which gas was fed to a small flame. As one spoke, the gas was alternately compressed and decompressed by the vibration of the membrane, resulting in higher and lower flames, respectively. Four mirrors were typically rotated as a unit to show the wave shapes: "when we speak to the apparatus, an undulatory band of light makes its appearance in the mirror. The upper edge of the luminous band appears to be carved into beautiful waves of various shapes and sizes, and when we sing different vowel sounds into the mouth-piece of the instrument, retaining the voice on a uniform level, the form or shape of the undulations visible in the mirror changes with every vowel. I thought that if I could discover the shape or form of vibration that was characteristic of the elements of English speech, I could depict these upon paper by photographic means for the information of my deaf pupils." (Bell, 1908, pp. 24-5)
Since Bell could not physically record the manometric flame patterns using photography and since the patterns were difficult to discern, he concentrated on another device, the phonautograph, which he also saw at the Institute of Technology. It consisted of a cone and membrane with a lever attached to the membrane; when one spoke into the cone, the lever vibrated. At the end of the lever was a bristle brush which traced the shape of the sound wave on a piece of glass covered with lampblack; the glass was moved horizontally in a direction perpendicular to the motion of the lever. "I proposed to use these glass plates as negatives, and by photographic means, print off copies of the tracings for the use of my pupils." (Bell, 1908, p. 26)
However, a comparison of phonautograph tracings and manometric flame shapes suggested to Bell that the phonautograph device needed extensive modification so that the tracings would match the flame shapes of the manometric capsule. Considering the phonautograph's geometry--with its thin, light membrane and the relatively heavy wooden lever and style--Bell was struck by the resemblance between the device and the structure of the human ear. The ear analogy suggested the sorts of modifications he might undertake to successfully replicate the flame shapes in the tracings of this device. The modifications aimed to make the analogy between technology and nature more literal. Bell sought to duplicate "the shape of the membrane of the human ear, the shapes of the bones attached to it, the mode of connection between the two, etc." (Bell, 1908, p. 29)
Following a suggestion from Dr. Clarence Blake, a distinguished aurist, Bell built an ear phonautograph in the summer of 1874, roughly the same time as he was conceiving his harp apparatus (see Figure 14). When one spoke into the cone, the eardrum and stapes, malleus and incus (all taken from a preserved human ear) were set into vibration; these vibrations were traced on smoked glass by a bristle brush attached to the end of the incus.
Figure 14: Bell's ear phonautograph. One speaks into A at top right, which causes the bones of the middle ear (B) to vibrate, tracing the pattern of the wave on the smoked glass (C).
From the phonautograph, Bell gained a tactile, 'hands-on' understanding of how speech was translated into an undulating wave by the vibrations of the bones of the ear. From his multiple telegraph experiments, Bell gained a similar understanding of how the vibrations of a reed or a combination of reeds could be translated into what he called an undulating electric current that would reproduce the sinusoidal pattern of the sounds.
At the urging of Gardiner Hubbard, Bell had begun keeping a notebook at around the time he applied for his patent. Notebooks are one of the ways in which inventors establish priority for their ideas. On February 18, 1876, Bell drew an ear with two different mechanical representations next to the bones (see Figure 15). On the left was an electromagnet, suggesting that the bones would serve a function similar to the steel reed he had so often placed over an electromagnet to transmit and receive complex tones. On the right was an iron cylinder attached to the bones and this vibrated in the center of a magnetized helix with an iron core. Bell had conducted experiments with such an arrangement, verifying that it could produce an undulatory current; he would later develop this mechanical representation into a telephone receiver (Bell, 1908). Beside the sketch, Bell wrote, "Make transmitting instrument after the model of the human ear. Make armature after the shape of the ossacles. Follow out the analogy of nature" *(Bell, 1876b, p. 13).
Figure 15: Bell's ear mental model. 'a' denotes the bones of the middle ear. The text under 'Fig 5' reads '(Helix & core, iron cylinder vibrated in helix)' and at the bottom right Mabel Bell notes that she copied the figure on February 21st.
The ear analogy provided Bell with a mental model that suggested possibilities and problem areas. Consider Bell's ear diagram (see Figure 15, again). It shows two possible arrangements of electromagnets that could be used to translate the vibrations of the ossicles into an electric current, one of which he had already used in building his Gallows telephone (the one on the left in the figure). Bell knew he could not include the ossicles in an actual speaking telegraph. Therefore, this sketch served as a reminder of the mental model he had been working with at least since June 30th, 1875, and possibly before.
Why did Bell need to state his mental model a year after he had designed a device which apparently embodied it? He could have been using his notebook to remind himself of his 'latitude and longitude' at this point. As noted above, this kind of reflection on one's representation and strategies frequently occurs when an expert is stuck or moving into a new domain. One could argue that Bell was simply making a statement for use in possible patent disputes, but the entry is not witnessed, nor did Bell ever use it in court. For Bell, his notebook was not just a record designed to establish his priority--it was a thinking tool.
As of February, 1876, Bell had a patent, but not a device which actually transmitted speech. Therefore, for Bell, the patent was not the end-point of a long process; it was the beginning of a new stage of research, of going from a patentable idea to a marketable product. At the beginning of this stage, he needed to reflect on his goals and remind himself of his mental model of how to achieve it.
The statement that he was 'following the analogy of nature' suggests that he was also reflecting on the heuristic he should use to accomplish this goal. Like confirmation and disconfirmation, 'follow the analogy of nature' is a higher-order heuristic used by other inventors as well as Bell. For example, the inventor of nylon, Wallace Hume Carothers, went back to nature and roughly imitated the way in which the silkworm puts together the building blocks for a protein (Friedel, 1994). A more recent example is provided by Misha Mahowald, who has made a career out of following the analogy of nature: she has built both a silicon retina and a silicon neuron, trying to imitate nature's solution as closely as possible (Mahowald & Douglas, 1991; Mahowald & Mead, 1991).
But telling a budding inventor that he or she should 'follow the analogy of nature' gives little guidance about what experiments to perform. This heuristic, like all heuristics, depends heavily on having an appropriate problem representation, in this case a mental model of nature's solution, and also some idea of how to map nature's solution onto the current problem domain. In order for Bell to copy nature, he had to have a detailed understanding of how the bones of the ear translated speech into undulating, sinusoidal waves, and how such waves could be reproduced electromechanically. Bell obtained this understanding from devices like the ear phonautograph.
The central claim of Bell's patent was that this undulating current was the best method to transmit sound, as opposed to the intermittent, or on-off, current commonly used in telegraphy. The undulatory current preserved the gradual changes in intensity produced by speech or musical tones; the intermittent current reduced these often subtle variations to an on-off code. In the first claim at the end of his patent 174,465, Bell claimed "a system of telegraphy in which the receiver is set in vibration by the employment of undulatory currents of electricity" *(Bell, 1908, pp. 459-60); his main example of how to do this was his reed mechanical representation, which could send telegraph signals, musical notes, or even speech. Bell's patent was breathtakingly broad: anyone who used the undulating current to transmit information could potentially be in conflict with Bell's claims.
Bell's patent and Gray's caveat were declared in interference with each other, a formal proceeding at the patent office in which the examiner has to determine whether, in the light of the interference, a patent should be granted to either party.
In fact, the two documents were very different. Gray's caveat covered a single method for transmitting speech. Bell's patent focused on a form of current that could be used in speech or telegraphy. Gray's patent heuristic was to cover speaking and harmonic telegraphy by patenting as many variations as possible; Bell's heuristic was to try to claim the whole landscape in a single patent.
The interference was resolved in favor of Bell's patent because it had arrived in the Patent Office a few hours earlier than Gray's caveat, though technically Gray still had three months in which to submit a patent and could also have contested Bell's claim in court. Gray's backers felt the speaking telegraph was a 'toy' that might be of occasional use over private lines, but would play no significant role in the transmission of multiple messages over long distances (Taylor, Unpublished Manuscript). Therefore, Gray did not contest Bell's patent until the commercial potential of the telephone became apparent.
After the interference had been voided, Bell learned from the patent examiner that the critical point of contention concerned a clause Bell had inserted at the last minute, in which he claimed the possibility of using variable resistance to create an undulating current. Gray's liquid transmitter depended on variable resistance. This conversation with the patent examiner became the source of endless debate during the years of litigation that followed, with some accusing Bell of outright theft of Gray's idea, in part because he eventually achieved the first transmission of speech with a device that looked similar to Gray's (Taylor, Unpublished Manuscript).
Bell received his patent on March 7, 1876. He had not yet successfully transmitted speech. From March 7 to 10, 1876, Bell did a series of experiments which culminated in the first transmission of speech. To show this process, I have employed protocol analysis, a technique used to record and analyze the problem-solving processes of participants in cognitive tasks (Ericsson & Simon, 1984). These participants are asked to speak aloud as they work, saying whatever comes into their minds. This is not the same as introspection--they are not being asked to reflect on the causes of their behavior, only report whatever mental steps they are going through. Their statements are used by the psychologist to create a problem behavior graph which documents their progress towards a solution.
We cannot protocol Bell for obvious reasons, but his notebook gives us a good record of his thoughts--he tries to record the steps in detail, pauses to consider alternatives and remind himself of goals. Tweney and Gooding have pioneered the use of protocol analysis with historical data; they conducted fine-grained studies of Faraday's cognitive processes (Gooding, 1990; Tweney, 1989). Like Bell, Faraday left extensive records--detailed notebooks, correspondence and artifacts. In fact, his notebook was seen as the model for other scientists and inventors.
Tweney and Gooding used Faraday's notebook to create graphical representations of his progress--we saw a brief example of this in Chapter 1. Gooding graphed each result, or hypothesis, and the manipulations that led Faraday to move from one state to another (see Figure 3 from Chapter 1). States were represented by boxes and operators by lines that went horizontally rightward for results that changed Faraday's knowledge state and vertically downward for results that did not. The problem-behavior graphs I created to document Bell's process differ in at least three respects from the conventions established by Gooding and Tweney :
(1) Instead of relying solely on symbols like squares for observations and triangles for shifts in goals, the components and the resulting combinations created by Bell are actually shown inside the symbols, to make it more transparent to a reader and to reveal the mechanical representations used by the inventor. Bell spends much of his time during this sequence of experiments substituting components in slots; these substitutions are illustrated with sketches, marked with plusses and minuses, to indicate whether a component was added or removed. (2) The line moves to the right in Gooding's graphs if there is a change in Faraday's knowledge state. In the Bell graphs below, the line moves right if Bell thinks the result is positive--he is generally quite explicit about whether he thought a result was positive, in terms of the current state of his research. Where he indicates that a result is somewhat positive, but less so than previous ones, the arrow will move rightward and downward, indicating some progress. This emphasis on positive and negative results comes out of Bell's notebook. He will occasionally pause to tell us what hypothesis he is working on, but mostly he wants to record configurations that do and don't produce a strong signal.
There is an alternate way of determining whether a result is positive or not. Barney Finn at the Smithsonian replicated a number of Bell's key experiments, using an oscilloscope to determine how strong a signal resulted (Finn, 1966). Bell did not have an oscilloscope, and relied on his own ear. Naturally, his perceptions were colored by his hopes, but what I intend to reconstruct is this pattern of perceptions and hopes, thereby avoiding the criticism that I might have simply imposed some post-hoc rational scheme on Bell's actual problem-solving process. This emphasis on viewing problem-solving in its actual context is characteristic of new work in what is called situated cognition (Bredo, 1994). We will have more to say about this work later.
(3) A slot diagram is also provided for each chain of experiments, to show the areas Bell was concentrating on and to suggest connections to his overall mental model. At the top of Figure 16 is a slot diagram, based on the circuit with which Bell began this sequences of experiments. The primary purpose of the slot diagram is to indicate the places where Bell made substitutions or changes; in this sense, the slot diagram also serves to define the problem space in which the inventor was working.
Figure 16: Slot diagram(at top left) and problem-behavior graph showing Bell's first series of experiments on March 8th.
The slot into which Bell substituted tuning forks, reeds and other armatures is labeled 'ossicles' to remind us that his goal was to find an armature which would 'follow the analogy of nature' and function like the ossicles, translating sound into an undulating electric current. The 'electromagnetic induction' slot indicates the place in his mental model where Bell had to solve the problem of how to translate the vibrations of an armature into an undulating current. Pushing the nature analogy, we might have referred to this as the 'organ of corti' slot; Bell knew roughly how this organ translated the vibrations of the bones into electrical impulses (Feist, 1993). Finally, there is a slot for 'power source', which in this chain of experiments meant a battery-- Bell could vary the number of cells.
On March 8th, Bell began by trying to transmit, clearly and distinctly, a tone using a familiar assemblage of components that had worked in the past: his steel reed mechanical representation as a receiver and a tuning fork, a la Helmholtz, as his transmitter (Gorman, Mehalik, Carlson, & Oblon, 1993). This experiment is really a replication of work done earlier. It was almost as though Bell were trying to establish a baseline, reminding himself of the quality of the results he could achieve with his familiar mechanical representations. He achieved the expected positive result--a clearly audible sound from the receiver.
Bell next tried adding an electromagnet of 'very high resistance'. This result was partially successful: a faint sound was heard from the receiver. This result was in line with expectations--increased resistance should produce a reduced signal. He may have been exploring what would happen if he tried to transmit over long distances, where the resistance of the line is a major factor, or he may simply have wanted to assess how strong the signal was by checking how much resistance it could overcome.
Next, he tried removing the electromagnet altogether, simply vibrating the fork over the wire. There was no sound--no surprise, because without the electromagnet, there was no mechanism for translating mechanical motion into undulating current. Bell in this case was probably checking to make certain he could distinguish the sound of the fork from that of the receiving reed. He had to listen to the reed by pressing his ear against it while vibrating the fork a short distance away. He knew how easy it would be to fool himself.
Next, he put the original electromagnet back in and removed the armature from the receiver, to listen directly to the coil. Here, he was working within the ossicles slot to see exactly what modifications would produce the strongest signal. Again, no sound. In this case, it was less clear that he expected a negative result. Bell had done previous experiments in which he heard sounds from a coil without an armature, but certainly not the kinds of tones he heard when he used a reed. Still, he probably wanted to check and make certain the tones he heard were really produced by the reed.
When he put an armature of soft iron on the receiver, he obtained a positive result.
Next, he shifted to the power source slot, removing it altogether. Bell had noted that the battery he was using was 'almost run down'--this experiment was probably an effort to make sure it was necessary. Bell was obsessed with simplicity: if he could transmit a clear signal without a battery in the circuit, so much the better. This attempt produced a negative result, as indicated by the arrow pointing to the right.
Robert Bruce, the distinguished Bell biographer, has described the set of experiments in Figure 16 as 'random' (Bruce, 1973). But Figure 16 shows they were anything but random: Bell moved systematically from slot to slot, removing or substituting one component at a time. Bruner called this heuristic 'conservative focusing' to distinguish it from another heuristic, 'focused gambling' (Bruner, 1956). The former involves a careful, systematic search through the problem space, varying only one thing at a time; the latter involves making a leap to a new part of the problem space by altering several variables at once. The two heuristics can be used in combination: an inventor could gamble by trying a radically different configuration of components, get a positive result, then return to a conservative focusing heuristic to see which changes were most important.
Bell's conservative focusing in this case was also a form of replication. He had already done versions of most of these experiments before. Bell had to review his mental model in his notebook before embarking on a new program of research; it seems he also needed to see if he could reproduce results obtained with familiar mechanical representations. He was in effect establishing a base-line for further experimentation.
At this point on March 8th, Bell made what in hindsight was a significant change, although it was still consistent with his conservative focusing heuristic. He inserted a dish of water into what had been the electromagnetic induction slot, which leads to a change in the slot diagram (see Figure 17).
This device was never patented, and we have no record of experiments Bell may have conducted with it. But the spark arrester may have served as a mechanical representation, reminding Bell how water could be used as medium of higher resistance in a circuit, one that would conduct induced currents of sufficient strength. The idea of turning this mechanical representation into a telephone transmitter probably came from his conversation with the examiner about the interference with Gray. This kind of opportunistic reasoning often occurs in design: a suggestion about another possible solution path is mated with previous work to produce an alternative approach (Simina & Kolodner, 1995).
The upper left-hand corner of Figure 17 shows a new slot diagram, in which the electromagnetic induction slot is replaced by a 'resistance medium' slot and the ossicles slot is replaced by 'contacts'. This new slot diagram is a reminder that the shift to liquids represents a transformation of the problem space, opening up new alternatives to explore. The 'resistance medium' slot indicated that Bell could alter the resistance of the water by adding acid, or substituting other materials for water: in his spark arrester application, he mentioned "carbon, plumbago, animal and vegetable tissues, and other substances offering a high resistance" (Bell, 1908). The 'contacts' slots represented the fact that Bell focused on the relative sizes and depths of the contacts in the water.
Figure 17: Slot diagram and problem-behavior graph after Bell introduces water as a resistance medium
If this approach were successful, it would apparently eliminate one of Bell's sub-goals: to make an armature after the shape of the ossicles. A contact dipping in water is not shaped like the ossicles! But it would still serve the same function: to translate the undulations of speech into electrical impulses. Bell seems to have blurred the traditional distinction between form and function: for him, form often suggested function. But once he had the function clearly in mind, he was willing to relax the constraints of the original form, in this case the shape of the ossicles, focusing instead on any arrangement which would translate sound waves into undulating electrical currents. Bell began with the experiment shown in the slot diagram in Figure 17; when one tine of the vibrating fork was placed in the water, a 'faint sound' resulted. The diagonal arrow to the next experiment indicates that this was a somewhat positive result. Next, he added a bit of acid to the water. This produced a much louder sound. Increasing the distance between the tuning fork and the conducting wire had no effect, which meant that Bell could ignore distance between contacts at this point. He then added a strip of brass to the conducting wire; this made the sound 'much louder' and completely immersing this wire in the liquid made the sound 'very loud' (Bell, 1876b, p. 37). Next, he decided to increase the size of the vibrating contact; to do this, he substituted a bell for the tuning fork. No sound resulted, nor was transmission improved when he substituted a steel wire for the brass one to see if the key was the difference in metals. When he replaced the bell with a piece of steel, the sound was again loud.
Note how Bell in this sequence of experiments employed the conservative focusing heuristic he had used in his earlier experiments on the same day, systematically altering one variable at a time to improve transmission. After acidulating the water, he quickly focused on the contacts slot. His heuristic was similar to what Platt (Platt, 1964) has called a strong inference strategy; he designed experiments that discriminated among hypotheses. He eliminated distance between contacts, which Gray regarded as the key to transmission, and also difference in the metals used in the contacts.
At this point, Bell paused, apparently at the end of his working day, and wrote down a new hypothesis under the heading "Thoughts", which can be paraphrased as follows: the best results could be obtained when the vibrating contact was smallest and the contact on the other end of the circuit was largest. This is shown in Figure 17 by a trapezoidal box, with a sketch in it that is based on the sketch Bell drew in his notebook. The vibrating contact was a small needle; the other contact was a large, flat ribbon which lay underneath the vibrating contact. The sketch included a speaking tube and membrane, borrowed from devices Bell had constructed earlier. The receiver was his familiar steel reed mechanical representation.
On the next day (March 9th), Bell and Watson built a version of this apparatus, using a sounding box instead of a speaking tube, a cork to attach the needle to the membrane, and a brass ribbon as the other contact. These substitutions are shown on the left-hand side of Figure 18. One of Bell's reed receivers was placed in another room. Bell listened while Watson sang, and was able to hear the pitch of Watson's voice. When Watson spoke, Bell heard "a confused muttering sound like speech but could not make out the sense. When Mr. Watson counted--I fancied I could perceive the articulations 'one, two, three, four, five'--but this may have been fancy--as I knew beforehand what to expect. However that may be I am certain that the inflection of the voice was represented" (Bell, 1876, p. 39). As far as Bell was concerned, this was a positive result--a similar result had convinced him that the Gallows telephone represented a patentable idea. Hence, the horizontal arrow to the next experiment, conducted on the next day.
Figure 18: Experiments by Bell and Watson on March 9th and 10th leading up the first transmission of speech
On March 10th, the two substituted a platinum pipe for the brass ribbon and a speaking tube for the sounding box. Bell spoke the famous words "Mr. Watson--Come here--I want to see you." (Bell, 1876, 40).
Here is the moment when the hero had reached his goal. It is even enshrined in a myth--that Bell spilled acid on his pants, and that is why he asked Watson to "come here." But this moment of heroic triumph is more apparent in hindsight. Arguably, the June 2nd experiment was more important, because it led to the patent.
Furthermore, Bell and Watson did not break out the champagne. Indeed, they continued to experiment. The two switched places and Watson read to Bell from a book: Bell could make out only a few words, but heard Watson say "Mr. Bell, do you understand what I say?" (Bell, 1876, 41). They continued to experiment, trying to figure out the exact circumstances which had produced the positive result, and also how to improve it. Adding cells to the battery produced a violent hissing. Bell realized that the transmitter was in effect operating as a battery, because one contact was brass and the other platinum. A black deposit quickly formed on the platinum contact.
To avoid these problems, Watson and Bell went back to their experiments with tuning forks, in effect replicating earlier work. Bell noted that the more deeply the prong of the fork was immersed in the water, the less the sound.
Here the contrast between Bell's design and Gray's becomes most apparent. The combination of devices Bell first used to transmit speech bears a superficial resemblance to the combination of devices described in Gray's caveat. But Gray's liquid transmitter depended on immersing a needle deeply in a vessel of water. Bell's liquid transmitter, in contrast, worked poorly if the needle or tuning fork went too deeply in water; he wanted to minimize the surface area of the vibrating contact and maximizing the area of the other contact.
From a modern standpoint, these differences might seem minor, but they were critical to the participants. In effect, Bell and Gray's liquid transmitters were different mechanical representations, because despite their superficial similarities, they embodied unique representations. Furthermore, Gray thought the transmission of speech might have required multiple speaking chambers, whereas Bell knew only one would be necessary.
The differences in the transmitters were mirrored by differences in the two receivers. Bell used his familiar reed mechanical representation, which could reproduce any tone. Gray used one of the receivers he had designed to discriminate and enhance single tones. In other words, Gray's receiver design would have been best suited to enhance a particular range of vocal tones, whereas Bell's was intended to reproduce any spoken sound. Again, superficial similarities that seem apparent in hindsight mask differences in the representations embodied in the devices.
After his caveat, Elisha Gray all but abandoned speaking telegraphy until June, after a major Centennial exhibition in Philadelphia, when he heard the human voice through one of Bell's telephones. Had Bell used a liquid transmitter on this occasion, Gray's surprise might have turned to suspicion. But despite his early success with the liquid transmitter, at the Centennial Bell demonstrated magnetic induction designs that looked more like the ones in his first patent. Improvements on this magneto design formed the basis of his second speaking telegraph patent, in 1877 . Why did Bell abandon the approach that led to the first transmission of speech?
Finn tested the Bell apparatus housed at the Smithsonian and concluded that, "Bell apparently abandoned the variable-resistance transmitter in favor of the magneto transmitter for the simple reason that the latter worked better and with greater consistency than the variable-resistance liquid transmitter he had designed, and this decision came after an impressively large number of experiments. My recent experiments confirm the validity of Bell's judgment." (Finn, 1966, p. 15)
Finn tested Bell's devices with an oscilloscope; Bell used his ear, and compared current results with what he had written about previous ones in his notebooks. Therefore, a fairer judge of Bell's successes may be his notebook record, which suggests that he continued to obtain positive results with the liquid transmitter long after March 10th, results at least as positive as any he had achieved with magneto designs.
Another possibility was that Bell wanted to keep his liquid experiments a secret, knowing that Gray was working on something similar. This implies some clever guesswork on Bell's part, or a spy at the patent office. All Bell ever admitted knowing was that his patent and Gray's caveat were in conflict over the matter of variable resistance.
There is a third possibility: that Bell saw the liquid transmitter primarily as a way of testing his mental model for the transmission of speech, not as a practical device. The liquid would need to be kept at just the right level. One can imagine running to 'top off the transmitter' every time the phone rang! Bell probably never seriously considered a practical liquid transmitter.
But how could a liquid transmitter confirm Bell's mental model? Contacts vibrating in water do not correspond in form to the bones of the middle ear. But they did serve the same function: translating the sinusoidal patterns of speech into an undulating current. The form of the ossicles was fading into the background, but its function remained paramount.
It is well to remember Freud's point about human behavior being overdetermined. In truth, some combination of all the above motives might account for Bell's decision. It is worth taking a brief look at the experiments Bell conducted between March 10th and May.
Recall that on March 10th, Bell realized his liquid transmitter was functioning as a battery. To avoid this problem, Bell used platinum on both contacts. On March 13th, his future father-in-law and principal backer Gardiner Hubbard dropped by and listened to the transmitter; he "was convinced that articulate sounds were transmitted along the wire--although the articulation was so muffled as to be to him unintelligible unless...he was informed beforehand of its sense" (Bell, 1876, p. 51). Bell concluded that "the experiments were on the whole satisfactory as demonstrating the fact that the timbre as well as the pitch of vocal sounds had been transmitted telegraphically" (Bell, 1876, p. 52). In other words, this experiment represented another confirmation of his undulating current mental model. Perhaps more importantly, this confirmation continued the process of converting Gardiner Hubbard to Bell's view of the potential benefits of the telephone.
After several frustrating efforts to improve transmission, on March 15th, Bell paused to reflect: "Instead of practical experiment I have come to the conclusion that I can best advance the subject by making a theoretical investigation of the effects produced upon a voltaic current by the vibration of the conducting wire in a liquid included in the circuit--and deducing thence the best way of increasing the amplitude of the electrical undulations so as to admit of the transmission of vocal utterance over long distances" (Bell, 1876 , p. 57).
In other words, Bell decided a search in what Klahr and Dunbar (Klahr, 1988) call the hypothesis space would be more profitable at this stage than further work in the experimental space, especially in light of his limited equipment and electrical skills. He sketched a series of thought experiments concerning the relationship between battery power, line resistance and resistance of the liquid, and sketched the shape of the undulations he thought might result from different combinations of these factors. Eventually an article in a handbook convinced him that even acidulated water would be over a million times more resistant than copper wire and would be far too great for the batteries he was using. The key to a liquid transmitter was to lower water resistance--either by acidulating the water, or bringing the contacts closer together, or both.
Bell carefully experimented with these options, and found if he separated the contacts by a thin film of water, the reed of the receiver often got stuck against the electromagnet. This led him to focus on the distance of the receiving reed from the coil, and on March 27th, to an experiment in which he used his two favorite forms of magneto receiver in a circuit. This represented his first experiment with an all-magneto design since March 8th. He obtained a positive result. Bell soon was back to experimenting with liquid devices, partly because they offered a solution to the problem of autograph telegraphy: sending letters over the wire. Bell's autograph telegraph experiments were part of his network of enterprises.
One particular experiment on April 5th, involving a transmitter in which a carbon contact dipped into mercury, allowed Bell to hear the difference between undulating and intermittent currents repeatedly and clearly, leading him to conclude "that my theory is correct--that musical notes which conflict with one another when transmitted by means of an intermittent (current) will not interfere with one another when the undulatory current is employed." (Bell, 1876b, p. 97--emphasis his). Another experimenter might have referred to this result as an error: the intermittent current kept interfering with the undulatory because the pencil was too short to be adjusted as precisely as necessary. But Bell had a knack for converting errors into positive results--in this case a positive result that also confirmed his theory.
On May 5th, Bell returned to magneto devices; from this point forward, the liquid transmitter virtually disappears from his notebook. He was preparing for a May 10, 1876, presentation to the American Academy of Arts and Sciences; the pressure of a deadline forced Bell to confirm that a magneto device could serve as both transmitter and receiver. In the talk, he placed much greater emphasis on his work with magneto devices, despite the fact that his notebooks suggested their performance was not consistently superior to that of liquid variable resistance devices: he could get either type to produce vowels, musical tones and even occasional phrases, but neither would permit consistent discrimination of consonants. On May 25th an audience at MIT heard occasional sentences transmitted from a neighboring house over a magneto telephone. "Vowels are faithfully reproduced; consonants are unrecognizable" reported the Boston Transcript (Bruce, 1973, p. 189).
Bell's exhibit at the. Philadelphia Centennial was hastily added to the program by Gardiner Hubbard, who played such a key role in putting Bell's work forward. One of the reasons I admire Bell is because he was a busy, overworked teacher like me, buried under papers he had to grade. He didn't want to take time from his teaching to go to the Centennial; his fiancee Mabel took him to the station and all but shoved him on the train.
Elisha Gray, in contrast, had an elaborate, carefully choreographed set of demonstrations ready, supported by Western Union. On June 25, the judges, accompanied by Dom Pedro, the Emperor of Brazil, listened to a long lecture by Gray and watched him demonstrate both musical and multiple telegraphy, but not speaking telegraphy.
The clever Hubbard had put Bell in the same hotel with three of the judges, so by the time they saw Gray's exhibit, they had already heard Bell's account of the scientific principles underlying his speaking telegraph. The judges then trudged off to see Bell's exhibit. It included multiple harmonic telegraph equipment, but also Bell's latest speaking telegraph--a magneto design that included a new receiver, which he had created by scavenging parts in Charles Williams' shop. Bell had found an iron cylinder with a rod running up the middle; when wire was wrapped around the rod, the whole apparatus became an electromagnet, with one pole represented by the pole of the cylinder and the other pole by the top of the rod. Bell added a lid of sheet iron, which vibrated in response to the undulating current from the transmitter.
Wires from this receiver ran to the corresponding transmitter in another part of the exhibit hall. Bell sang and shouted into this transmitter while Sir William Thomson, one of the judges, listened at the receiving end. He heard the words, "Do you understand what I say?", and shouted, "I must see Mr. Bell!" Thomson ran to find Bell, reported the success, and went back to hear more. Dom Pedro was next, heard part of Hamlet's soliloquy, and also rushed off to congratulate Bell. Even Elisha Gray heard "Aye, there's the rub" faintly when he took his turn at the receiver (Bruce, 1973, p. 197). Bell's use of a familiar passage was a clever way of insuring that listeners could fill in the gaps in the faint and unsteady transmission.
The delighted and surprised reaction of his listeners would be echoed time and time again when Bell, Watson and others took their invention 'on the road' and did live demonstrations. For a professional telegrapher like Gray, this invention had always been subsidiary to the telegraph. As he said in a letter to his attorney, A.L. Hayes in October of 1875:
Bell seems to be spending all his energies on [sic] talking telegraph. While this is very interesting scientifically it has no commercial value at present, for they can do much more business over a line by methods already in use than by that system. I don't want at present to spend my time and money for that which will bring no return.
He also publicly conceded all priority in matters related to speaking telegraphy in a letter to Bell on March 5th, 1877, in which he said,
Of course you had no means of knowing what I had done in the matter of transmitting vocal sounds. When, however, you see the specification, you will see that the fundamental principles are contained therein. I do not, however, claim even the credit of inventing it, as I do not believe a mere description of an idea that has never been reduced to practice, --in the strict sense of that phrase,--should be dignified with the name invention
In later years Gray regretted this concession, especially given the fact that Bell got a patent without achieving a reduction to practice. But Gray also had to admit that Bell was the first to achieve spoken transmission, and that his electromagnetic induction design was original: "I thought it would be impossible to make a practical working speaking telephone on the principle shown by Professor Bell, to wit: generating electric currents with the power of the voice, as it seemed to me then that the vibrations were so slight in amplitude and the inductor necessarily so light that the currents thus generated would be too feeble for practical purposes." (1880, Part I, 142-3) Eventually, Gray designed and patented several magneto speaking telegraphs of his own, in an effort to circumvent Bell's patent. He also built and tested his liquid transmitter after the Centennial, and applied for patents in which it would be used in combination with various receivers. Again, Gray relied on a patent-combinations heuristic, using familiar mechanical representations like the washbasin-electromagnet design as both transmitter and receiver in combination with other mechanical representations, including the liquid transmitter featured in his caveat (Gorman, Mehalik, Carlson, & Oblon, 1993).
Bell did not even bother to demonstrate his liquid transmitter at the Centennial, and liquid designs virtually disappear from his notebook. The success of the liquid transmitter may have disconfirmed Bell's idea that the form of the armature ought to be modeled on the ossicles. On September 27th, Bell wondered if he should "try to use the membrane of the human ear as a transmitter. Attach light piece of iron or steel to maleus--having removed stapes and incus." (Bell, 1876, Vol II, p. 83) In this extraordinary passage, Bell reminds us that the ear still serves as a mental model. Attaching an armature to the maleus is similar to his ear phonautograph, in which a brush was attached to all three bones of the middle ear. By removing the stapes and the incus, Bell has removed the hinge that he thought was essential in his February 21st sketch of the ear mental model. The form of the ossicles was gradually disappearing.
His first production telephones substituted a heavy metal diaphragm for the hinged armature suggested by the ossicles analogy, but otherwise they were identical to devices used in his first patent. His discovery of the benefits of a metal diaphragm involves the way in which he used his notebooks as a tool for reflection. On July 11, 1876, Bell tried attaching a disk of tagger's iron to the membrane of the transmitter, replacing the metal strip he usually used. He found sounds were louder with the disk than with the strip. He experimented with a circuit of 19660 ohms resistance and ten battery cells, and found that "the softer the initial articulation the more distinct was the utterance at the other end of the line" (Bell, 1876, Vol II, p. 28). Bell was at this point working to achieve long-distance transmission, and in this sequence of experiments, he occasionally used water to simulate the high resistance of a long-distance line.
The iron disk disappeared as Bell went into a long sequence of multiple telegraph experiments, followed by experiments using springs on the membrane, which led to his insight on September 27th that the spring need not be modeled after the form of the ossicles. Then on October 2nd, he re-read his notebook and noticed the July 11th experiment with the iron disk. He could not imagine why they hand not tried this again. He and Watson glued a steel disk to the membrane. "The articulation was much more distinct" (Bell, 1876, Vol II, p. 3). On October 7th, the two men carried on an enthusiastic telephone conversation, in which Watson said, "Success has at last [attended] our efforts" (Bell, 1876, Vol III, p. 4). The fact that Bell could not make out the word 'attended' scarcely dampened their enthusiasm. Long conversations followed, and were recorded in the notebook.
In January, 1877, Bell submitted a second patent that emphasized speaking telegraphy. The membrane was now gone altogether; in its place was a heavy plate of iron or steel, whose position with respect to an electromagnet or permanent magnet could be adjusted to produce the best transmission or reception. Bell and Watson's first production telephones were built along these lines, but were quickly superseded by better transmitters using carbon as a medium of variable resistance. Bell and Watson also put together an effective 'road show' in which Bell would place a receiver in front of an audience and Watson would sing to them from a remote location (Bruce, 1973). Just as at the Centennial, these shows had a magical effect on audiences. Never mind that much of the effect depended on the way Watson bellowed into the transmitter. Bell's telephone transmitter was quickly superseded by better devices (Carlson, 1989), but he had recognized the importance of transmitting speech and played a major role in creating a market for this new technology.
Invention involves more than creating a device; to borrow the sociologist John Law's felicitous phrase, it is an exercise in heterogeneous engineering (Law, 1987). What Law means is that successful inventors build a network of technologies, patents, backers, buyers--even, in Bell's case, scientists. Bell did not build this network all by himself; instead, he recruited allies like Gardiner Hubbard, Sir William Thomson and others who promoted his invention. It was Hubbard who created the Bell Corporation and made his son-in-law a millionaire. Gray, meanwhile, successfully developed an improved form of duplex and used it over long-distance lines starting in May of 1877. He referred to this duplex as a telephone, in the spirit of Philip Reis' original invention, but what Gray had in mind was a harmonic telegraph. He could send two messages at the same time over a long-distance line in a way that did not interfere with all the local Morse telegraph messages that were being sent over the same wires at the same time (Gray, 1977). This was a major accomplishment. But the entire technological front had been transformed by Bell's invention, and conquering the old reverse salient was now a minor victory.
Let us revisit our generalizations, and see whether they can help us compare the cognitive processes of Bell and Gray and extract meaningful lessons, substituting the term inventor for discoverer.
1. Invention depends on establishing that a problem is significant enough to be labeled an important achievement.
One way for inventors to find significant problems is to focus on reverse salients. Kilby and Noyce, inventors of the microchip, did this with great success (Reid, 1984). Elisha Gray, however, found that Bell's invention transformed the entire communications industry in a way that made the old reverse salient a minor problem. Bell sought to solve a problem whose significance only he really appreciated.
2. Invention depends on transforming that problem into a form that suggests a promising path to solution which includes locating and transforming the necessary mechanical representations.
Here we have substituted the new term mechanical representation for data. Part of the mind of the inventor is embodied in the special components she crafts. This is often true of discoverers as well.
Gray certainly transformed the technologies available for multiple telegraphy, creating a whole new set of mechanical representations, and patenting combinations among them. Bell, in contrast, sought to come up with a single, best mechanical representation that would embody his mental model of how speech, or telegraph signals, or music might be transmitted and received.
To put it in other terms, Gray's knowledge was more in his devices and Bell's in his sketches and notebooks. Gray was comfortable building a proliferation of sophisticated devices; Bell preferred thought experiments and theoretical reflections, imagining how systems might work.
When I give talks about Gray and Bell, I am often challenged by historians, who claim this combinatory or matrix style of Gray's is simply the result of the spotty records he left--if he had kept the same sort of detailed records as Bell, his cognitive style would look more similar.
First of all, I think it is significant that he did not keep records as detailed as Bell's. Record-keeping is a reflection of cognitive style. Bell used his notebooks as a thinking tool, as well as a means of creating a powerful heroic narrative of his invention. That reflects his goals and style. As early as 1873, he adopted the theme, or role, of a theoretical inventor.
Gray, in contrast, embodied his thinking in devices. That's why he thought his caveat contained the fundamental principles for transmitting speech--even though he nowhere discussed the undulating current, or any of the other theoretical matters raised by Bell in his patent. For Gray, the principles were embodied in the device, which told the whole story.
While Bell tried to find a single, simple device that would represent his goal, Gray created multiple devices which were better suited to different telegraph applications and which would allow him to patent different approaches to the problem of telegraphy. When asked to recall his invention process, he listed devices and experiments conducted with them. Gray left almost no other records because he didn't need them--his devices were his memory, and practically spoke for themselves.
One could try to adapt the language of the dual-space approach to scientific reasoning. Recall that Klahr and Dunbar found two cognitive styles among participants in one of their Big Trak experiments: theorists, who spent more time searching a hypothesis space, and experimenters, who spent more time in an experiment space (Klahr, 1988). Bell's style resembles that of the theorists; he spent a good deal of time considering alternate hypothesis for designs, conducting thought experiments and even reflecting on his overall mental model in his notebook.
Gray bears more resemblance to the experimenters, in his preference for creating devices rather than thinking about what sort of current would best transmit speech or musical tones. But the term experimentalist isn't quite right for Gray. He would be better described as working in a space of mechanical representations, developing multiple variations. Bell, in contrast, sought to develop the simplest possibl