The role of imagistic simulation in scientific thought experiments
Clement, J. J. (2009). The Role of Imagistic Simulation in Scientific Thought Experiments. Topics In Cognitive Science, 1(4), 686–710. doi:10.1111/j.1756-8765.2009.01031.x
Summary
In this paper, Clement poses the fundamental paradox of thought experiments as being “How can findings that carry conviction result from a new experiment conducted entirely within the head?” (pg. 687). He attempts to provide a resolution to this paradox based on the idea of “imagistic simulation” (a.k.a. mental simulation, mental imagery, etc.) with evidence provided through a case study of a single expert subject (S2). S2 is posed with the following “spring problem”:
A weight is hung on a spring (Fig. 1). The original spring is replaced with a spring made of the same kind of wire, with the same number of coils, but with coils that are twice as wide in diameter. Will the spring stretch from its natural length more, less, or the same amount under the same weight? (Assume the mass of the spring is negligible). Why do you think so? (pg. 689)
Clement specifies his definition of “thought experiment” (TE) as being “the act of considering an untested, concrete system (the ‘experiment’ or case) and attempting to predict aspects of its behavior” (pg. 690-1). He isolates a number of TEs produced by S2, and analyzes the use of imagistic simulation in those TEs. He finds that S2 spontaneously engaged in “personal action projection (spontaneously redescribing a system action in terms of a human action) consistent with the use of kinesthetic imagery, depictive getures (gestures that depict objects, forces, locations, or movements of entities), and imagery reports” (pg. 694). Some of these are characteristic of using static imagery, but others are characteristic of dynamic imagery.
To explain the use of dynamic imagery, Clement appeals to the idea of motor schema theory in which imagistic simulations are driven by the use of motor programs/schema. Specifically, he identifies four possible components to an imagistic simulation which allow such simulations to apply to situations which have not previously been encountered:
- Applying a schema to a use outside its normal domain
- Converting implicit knowledge into explicit knowledge
- Including spatial reasoning
- Combining multiple schemas into a compound simulation
Additionally, Clement argues that imagistic simulations are used to generate “enhanced” imagery:
…the main source of conviction in the simulations is the tapping of implicit knowledge embedded in motor schemas and its conversion into explicit knowledge. The extreme case makes differences in implicit expectations larger and more ‘perceivable’ in this case. (pg. 698)
Clement argues that this formulation of imagistic simulation resolves the TE paradox:
To address the TE paradox, the idea of perceptual motor schemas running imagistic simulations, and the four more specific sources of conviction within imagistic simulations… can account for ways that a TE can feel empirical (via the inspection of imagery) or necessary (via confident schema extension or spatial reasoning). Yet these processes actually involve a considerable amount of nonformal reasoning and inference that goes beyond prior observations. (pg. 704)
In discussing the case study with S2, Clement also touches on the distinction between evaluative (disconfirmatory/confirmatory) and generative thought experiments.
Takeaways
I like this characterization of what thought experiments (and perhaps, even, mental simulations more generally) are; I think Clement is right in tying the use of thought experiments to action and perception.