quinn@unix.cis.pitt.edu (Clark Quinn) (10/19/89)
Don Norman's response to Thom Gillespie's question about metaphors and mental models raises some more questions (as intended). While I basically agree with Don's characterization of metaphor (although I really think we are talking about analogy), I want to paint mental models in a slightly different way (there, a metaphor). First, I am going to discuss what I think the distinction is, and then discuss each in greater detail. The confusion between metaphor and model lies in that both consist of using a representation, easier to operate in, to solve problems or understand information in a new or unfamiliar domain. In the case of metaphor, the representation that is manipulable is a familiar domain which is used to apply to a different domain. Models are a simplified, conceptual representation of the domain, removed from many of the real world attributes. The simplified representation allows prediction and inference about the domain. Unfortunately, metaphors can serve as a mental model. This is unfortunate both because it confuses the issue ("don't tell me that a mental model is a bunch of metaphors"), and that people tend to misuse metaphors as a result of thinking they are models. As I mentioned in the beginning, Don's description of metaphor struck me more as a description of analogy (of course, analogy was the topic of my dissertation). What is the difference between analogy and metaphor? I never have had a suitable explanation of the distinction. I have reverted to lumping them together, but if pressed I back up and leave metaphor to linguistic purposes and use analogy for problem-solving. I have this intuitive feeling that metaphors are softer and squishier than analogies (that metaphors only account for some of the relevant features of a domain, and analogies are more comprehensive), but the lines blur enough for me to consider them roughly equivalent. So, when I say metaphor, I mean analogy. If you feel different, *please* tell me why! In analogy, when we need to understand something new, or we want to solve an unfamiliar problem, we must fall back on what we know. Typically, we access a domain that seems similar and try to extend the relationships from the known domain to the new. Teachers may also provide us with analogies to help us. Psychological evidence (Ratterman & Gentner, 1987; Gick & Holyoak, 1980, 1983; Quinn, 1989) suggests that we use given analogies reasonably well, but don't come up with them ourselves with any reasonable efficiency. Models, typically, are explanatory conceptual models that underlie the operation of observed phenomena. While an analogy can serve as a mental model (such as flow in water explaining flow in circuits) they often break down in extreme cases (current through a constriction increases while current in a resistor is consistent with the current of the entire circuit). Models typically are the physical laws that are operating to produce phenomena (like atomic structure predicting elemental properties). There is some evidence that people reason effectively, given good models (Keiras & Bovair, 1983), but the evidence also suggests that people do reason with models (Clement, 1988), incomplete and sketchy ones if necessary (Norman, 1983). This is, I hope, a slightly more precise distinction between models and metaphors (analogies). I don't share Don's disenchantment with mental models, but perhaps that is because I'm now working on mental models for science understanding (can you say "vested interest"?). -- Clark Clark N. Quinn Learning Research and Development Center University of Pittsburgh Pittsburgh, PA 15260 (412) 624-9581 quinn@unix.cis.pitt.edu Ratterman, M.J., & Gentner, D.E.(1987) "Analogy and similarity: determinants of accessibility and inferential soundness." Proceedings of the Ninth Annual Cognitive Science Society Conference. Gick, M.L., & Holyoak, K.J.(1980) "Analogical problem solving." Cognitive Psychology. Gick, M.L., & Holyoak, K.J.(1983) "Schema induction and analogical transfer." Cognitive Psychology. Quinn, C.N. (1989) "Analogical process performance and training." Unpublished Doctoral Dissertation. Keiras, D.E., & Bovair, S. (1983). "The role of a mental model in learning to operate a device." TR 13. University of Arizona. Clement, J. (To appear) "Learning via model construction and criticism: protocol evidence on sources of creativity in science." In J. Glover, R. Ronning, & C. Reynolds "Handbook of creativity: assessment, theory, and research. New York, NY: Plenum. Norman, D.A. (1983) "Some observations on mental models." In D.E. Gentner & A.L. Stevens "Mental Models".