1. A dilemma for Machery
The large number of words we have for potentially deceptive things attests to the fact that they label a phenomenon that is important to us. Nonetheless, the knowledge often essential to distinguishing between the real thing and something else – causal knowledge – is left out of the prototype and exemplar accounts. Thus, Machery (Reference Machery2009) says, “neither prototypes nor exemplars store causal knowledge,” and so tasks that require subjects “bring some causal knowledge to bear” (Doing without Concepts, p. 187) are evidence for a third theory of concepts, the theory or knowledge account. As a consequence, very good mimics and imitations, whose similarity to the real thing is often undetectable to the casual observer, answer to the criterion given by prototype and exemplar theories. Many red pandas look a great deal like raccoons, but they are not raccoons (Flynn et al. Reference Flynn, Nedbal, Dragoo and Honeycutt2000; Sato et al. Reference Sato, Wolsan, Minami, Hosoda, Sinaga, Hiyama, Yamaguchi and Suzuki2009). Seeming gold rings may be made of copper, cubic zirconias fool many people who take them to be diamonds, and gopher snakes are close indeed in appearance to rattlers, though they are not poisonous.
Machery argues that typically we have at least three independent but co-referential concepts for each kind of thing: a prototypical concept, an exemplar concept, and a knowledge/theory concept (see Murphy [2002] for the “knowledge” label). But there is a problem: Cases of good fakes (e.g., cubic zirconias vs. diamonds) either fit a correct use of the prototypical or exemplar concept or they do not. Suppose they do; if so, then the prototypical or exemplar concept of a diamond will apply to things that the knowledge/theory account concept does not, and the two will not be co-referential.
Alternatively, suppose that cubic zirconias that fit the prototypical concept are not correctly called diamonds. In this case, their independence is threatened. The criteria given by the knowledge/theory account are able to overrule those of the other two. Machery resists the idea that the knowledge/theory concept can so dominate (Ch. 3, sect. 3.3). However, given his claim that the sentence, “Tina Turner is a grandmother” (Machery Reference Machery2009, p. 72) is true under one interpretation and false under another, the example shows that if one type does not dominate, different uses of “grandmother” will vary in reference.
The argumentative context in which Machery considers fakes leads him to restrict his attention to sentences. Further, his intuition does not clearly say that “Fake dollars are dollars” is false (2009, p. 72). But, as Machery insists, the range of the use of concepts covers far more, and intuitions about sentences do not settle whether criteria from the knowledge/theory account will overrule in practice.
2. A more general problem
The failure to encode causal knowledge creates another problem for prototype and exemplar concepts and, by implication, Machery's thesis. Experimental work in Machery's discussion of prototype and exemplar theories is largely represented by descriptions of testing subjects on lists, sentences, pictures, and drawings, including patterns of dots. In contrast, Murphy (Reference Murphy2002, p. 60) remarks that his knowledge/theory account rejects the idea that we “learn concepts in isolation from everything else (as is the case in many psychology experiments).” But our classifications of objects need to work to identify and track them in a dynamical environment. That sort of task carries quite different demands; among other things, classification needs to yield some clues about how our environment will unfold.
Infants have a capacity relevant to identifying kinds in a changing environment, one that Carey and Xu (Reference Carey and & F.2001) claim controversially does not appear until 12 months. That is, at some point infants expect kinds of objects to persist and not change into another kind. Before then, mere spatial-temporal continuity dominates; a duck moving behind a screen and an emerging rabbit do not have to be two distinct objects. Knowledge that kinds persist and do not turn into one another looks like causal knowledge of how things work; and Carey and Xu maintain it is preceded by other causal knowledge. Further, the presumption that kinds persist facilitates the acquisition of knowledge about how objects of some kind interact with their environment. Such knowledge is important because it enables one to anticipate some of what will happen.
From this perspective, there is at least a tension between saying that concepts are important in classifying and saying that they do not encode causal knowledge. It is unclear why using non-causal concepts would have any survival advantages, except in situations where the tasks to be performed have restricted success conditions. We look at such a task in the next section.
3. Conclusion
Prototypes and exemplar theories may still characterize what is needed to fulfill some of the tasks vision needs to undertake. One is that of perceptual organization. Our vision at one stage is a succession of saccades; the successive-saccades stage leads to our experience of a scene of stable objects. This important result appears to be driven by gestalt groupings, but it can be facilitated by top-down categorizing that may in many cases be triggered by similarity to a prototype or exemplar (Öğmen Reference Öğmen2007; Öğmen et al. Reference Öğmen, Otto and Herzog2006). Success in this sort of task is simply getting some organization. It can be achieved even if one is being taken in by fakes and the faux.
The preceding material suggests that there are layers to our uses of concepts, ones distinguishable in terms of the complexity of the knowledge needed. In creatures made for action, perceptual organization is required for almost any vision-guided action. Its success conditions may be much less demanding than those of another task, anticipating how one's environment is going to unfold. Finally, human cognitive life and public communication, among other things, have a considerable interest in getting it right, and not being taken in by potential deception. These different stages can be seen as posing less and more demanding tasks for our uses of concepts. Machery has instead posited multiple independent processes, but we have seen reasons for questioning the independence. That said, one should nonetheless expect that bold hypotheses from a subtle mind like Machery's will prove more resilient than one might first expect.
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1. A dilemma for Machery
The large number of words we have for potentially deceptive things attests to the fact that they label a phenomenon that is important to us. Nonetheless, the knowledge often essential to distinguishing between the real thing and something else – causal knowledge – is left out of the prototype and exemplar accounts. Thus, Machery (Reference Machery2009) says, “neither prototypes nor exemplars store causal knowledge,” and so tasks that require subjects “bring some causal knowledge to bear” (Doing without Concepts, p. 187) are evidence for a third theory of concepts, the theory or knowledge account. As a consequence, very good mimics and imitations, whose similarity to the real thing is often undetectable to the casual observer, answer to the criterion given by prototype and exemplar theories. Many red pandas look a great deal like raccoons, but they are not raccoons (Flynn et al. Reference Flynn, Nedbal, Dragoo and Honeycutt2000; Sato et al. Reference Sato, Wolsan, Minami, Hosoda, Sinaga, Hiyama, Yamaguchi and Suzuki2009). Seeming gold rings may be made of copper, cubic zirconias fool many people who take them to be diamonds, and gopher snakes are close indeed in appearance to rattlers, though they are not poisonous.
Machery argues that typically we have at least three independent but co-referential concepts for each kind of thing: a prototypical concept, an exemplar concept, and a knowledge/theory concept (see Murphy [2002] for the “knowledge” label). But there is a problem: Cases of good fakes (e.g., cubic zirconias vs. diamonds) either fit a correct use of the prototypical or exemplar concept or they do not. Suppose they do; if so, then the prototypical or exemplar concept of a diamond will apply to things that the knowledge/theory account concept does not, and the two will not be co-referential.
Alternatively, suppose that cubic zirconias that fit the prototypical concept are not correctly called diamonds. In this case, their independence is threatened. The criteria given by the knowledge/theory account are able to overrule those of the other two. Machery resists the idea that the knowledge/theory concept can so dominate (Ch. 3, sect. 3.3). However, given his claim that the sentence, “Tina Turner is a grandmother” (Machery Reference Machery2009, p. 72) is true under one interpretation and false under another, the example shows that if one type does not dominate, different uses of “grandmother” will vary in reference.
The argumentative context in which Machery considers fakes leads him to restrict his attention to sentences. Further, his intuition does not clearly say that “Fake dollars are dollars” is false (2009, p. 72). But, as Machery insists, the range of the use of concepts covers far more, and intuitions about sentences do not settle whether criteria from the knowledge/theory account will overrule in practice.
2. A more general problem
The failure to encode causal knowledge creates another problem for prototype and exemplar concepts and, by implication, Machery's thesis. Experimental work in Machery's discussion of prototype and exemplar theories is largely represented by descriptions of testing subjects on lists, sentences, pictures, and drawings, including patterns of dots. In contrast, Murphy (Reference Murphy2002, p. 60) remarks that his knowledge/theory account rejects the idea that we “learn concepts in isolation from everything else (as is the case in many psychology experiments).” But our classifications of objects need to work to identify and track them in a dynamical environment. That sort of task carries quite different demands; among other things, classification needs to yield some clues about how our environment will unfold.
Infants have a capacity relevant to identifying kinds in a changing environment, one that Carey and Xu (Reference Carey and & F.2001) claim controversially does not appear until 12 months. That is, at some point infants expect kinds of objects to persist and not change into another kind. Before then, mere spatial-temporal continuity dominates; a duck moving behind a screen and an emerging rabbit do not have to be two distinct objects. Knowledge that kinds persist and do not turn into one another looks like causal knowledge of how things work; and Carey and Xu maintain it is preceded by other causal knowledge. Further, the presumption that kinds persist facilitates the acquisition of knowledge about how objects of some kind interact with their environment. Such knowledge is important because it enables one to anticipate some of what will happen.
From this perspective, there is at least a tension between saying that concepts are important in classifying and saying that they do not encode causal knowledge. It is unclear why using non-causal concepts would have any survival advantages, except in situations where the tasks to be performed have restricted success conditions. We look at such a task in the next section.
3. Conclusion
Prototypes and exemplar theories may still characterize what is needed to fulfill some of the tasks vision needs to undertake. One is that of perceptual organization. Our vision at one stage is a succession of saccades; the successive-saccades stage leads to our experience of a scene of stable objects. This important result appears to be driven by gestalt groupings, but it can be facilitated by top-down categorizing that may in many cases be triggered by similarity to a prototype or exemplar (Öğmen Reference Öğmen2007; Öğmen et al. Reference Öğmen, Otto and Herzog2006). Success in this sort of task is simply getting some organization. It can be achieved even if one is being taken in by fakes and the faux.
The preceding material suggests that there are layers to our uses of concepts, ones distinguishable in terms of the complexity of the knowledge needed. In creatures made for action, perceptual organization is required for almost any vision-guided action. Its success conditions may be much less demanding than those of another task, anticipating how one's environment is going to unfold. Finally, human cognitive life and public communication, among other things, have a considerable interest in getting it right, and not being taken in by potential deception. These different stages can be seen as posing less and more demanding tasks for our uses of concepts. Machery has instead posited multiple independent processes, but we have seen reasons for questioning the independence. That said, one should nonetheless expect that bold hypotheses from a subtle mind like Machery's will prove more resilient than one might first expect.
ACKNOWLEDGMENTS
I am indebted to Josh Brown and Josh Weisberg for discussions of this material.