A Framework for Comparing Inventors and Reflecting on the Design Process (Michael E. Gorman, W. Bernard Carlson)

• 1.1 Mental Models. A mental model is a dynamic, visual representation of a potential devices that an inventor can 'run' in his or her mind. For example, Edison began his kinetoscope, or motion picture invention, with a mental model of a machine that would do 'for the Eye what the phonograph does for the Ear.' Like the phonograph, Edison intended that the kinetoscope would be used by individuals for both recording and viewing moving pictures. Consequently, this mental model led Edison to develop a peep show and not a projecting machine. There is a growing literature on mental models in cognitive psychology, but this work does not focus on inventors.
• 1.2 Slots. An inventor's mental model can be divided into areas of concentration called 'slots,' following the cognitive psychology literature. Slots are our reconstruction of the way an inventor subdivides a problem. With the kinetoscope, Edison's mental model suggested that he needed a component analogous to the sound groove on the recording cylinder on his phonograph. Consequently, Edison initially sought a way to create a spiral of tiny photographs on a revolving drum.
• 1.3 Mechanical Representations. Inventors have familiar devices or 'stock solutions' that they insert in slots in their mental models. A slot is analogous to a variable; a mechanical representation is analogous to a value for a variable. For example, Edison's phonograph mental model did not include a mechanism for interrupting motion so that the eye could register the illusion of a smooth flow of images. He therefore needed to create a slot for a device that would cause the cylinder to pause briefly. In this slot, he inserted a double-action pawl he had used on his stock tickers to convert circular motion into linear motion; we refer to this double-action pawl as a mechanical representation. Because an inventor may manipulate these devices not only on the workbench but also in his or her imagination or in sketches, we refer to these devices as representations and not simply as components or objects.
• 1.4 Strategies. Inventors, like scientists, mathematicians and other problem-solvers, also employ a variety of strategies.
• • 1.4.1 Heuristics or 'rules of thumb' help reduce the complexity of a problem and suggest a path to solution. Two good examples that students can relate to are
  • • 1.4.1.1. Conservative focusing, or vary one variable: An inventor who follows this heuristic will change one mechanical representation while holding all other features of the device constant. Bell frequently used this strategy.
    • 1.4.1.2 Focused gambling: In contrast, an inventor following this strategy will deliberately change several features of the device at once, in hopes of discovering a much more promising approach. Edison frequently did this.
  • 1.4.2 Algorithms are used by experts to solve familiar sub-problems.

2. Using the framework to compare and reflect.

• 2.1 Students could first be asked to figure out, from their notes, what their own mental models, mechanical representations and heuristics were, and how these elements interacted. Was their mental model dictated by those of previous inventors, or did they explore radically different alternatives? Did they rely primarily on conservative focusing, or did they gamble on very different design alternatives?
• 2.2 A class could then be devoted to inter-group comparisons, with each group presenting its perception of its own processes.
• 2.3 In this same class (or classes) comparisons with actual inventors should be made. This kind of discussion best accompanies the unit on the telephone, because the three major inventors have been compared using this framework.

Unless otherwise noted this page and all its contents and subdocuments are copyright 1994 by Michael E. Gorman

Quoted in W. Bernard Carlson and Michael E. Gorman, 'Understanding Invention as a Cognitive Process: The Case of Thomas Edison and Early Motion Pictures, 1888-1891', Social Studies of Science, 1990, 20: 387-430, 396. This article includes a detailed discussion of how this cognitive framework illuminates the invention of the kinetoscope. For good reviews, see D. Gentner and A.L. Stevens, Mental Models. (Lawrence Erlbaum Associates, 1983), 99-129 and W.B. Rouse and N.M. Morris 'On Looking Into the Black Box: Prospects and Limits in the Search for Mental Models', Psychological Bulletin, 1986, 100:349-363. Ronald Finke deals with the role of visualization in invention by asking experimental subjects to mentally construct new devices out of simple shapes. In effect, these subjects are creating and manipulating mental models, though Finke does not cite this literature, nor does he include comparative case-studies detailing the processes of actual inventors. See R. Finke, Creative Imagery: Discoveries and Inventions in Visualization (Lawrence Erlbaum Associates, 1990). This term is adapted from R.J. Weber and D.N. Perkins, 'How to Invent Artifacts and Ideas', New Ideas in Psychology, 1989, 7: 49-72.  Reese V. Jenkins suggested that Edison frequently employed certain mechanical and electrical components (such as the cylinder and stylus) in his inventions. See his article, 'Elements of Style: Continuities in EdisonÕs Thinking,' Annals of the New York Academy of Sciences, 1984, 424: 149-62. To some extent, mechanical representations resemble the technical structures which Bertrand Gille defined as the basic tools and elements underlying all technology. See his History of Techniques, (Gordon and Breach, 1986), vol. 1, 10-14. Finally, Eugene Ferguson has described how several technologists catalogued mechanical movements; one example is the mechanical alphabet created in the eighteenth century by the Swedish engineer Christopher Polhem. See his article 'The MindÕs Eye: Nonverbal Thought in Technology,' Science, 1977, 197: 827-36. For a discussion of how Edison used this mechanical representation in the kinetoscope, consult Carlson and Gorman, op. cit. (12), 398-9. For examples of how he used it throughout his telegraph work, see Reese V. Jenkins et al., eds., The Papers of Thomas A. Edison, Vol. 1: The Making of an Inventor, February 1847-June 1873 (Johns Hopkins University Press, 1989), especially 200, 323-5, 370, 407, and 428. Cognitive psychologists have studied scientific heuristics in detail, using experimental, computational and historical methods; see Gorman, Simulating Science Bloomington: Indiana University Press, 1992. Very little attention has been paid to heuristics used by inventors; see Weber and Perkins, op. cit. for an exception. In fact, much of the material for this lecture came from Gorman, Mehalik, Carlson & Oblon **