5
The Modularity Theory
explanation in real science. There are two parts to this: the theory’s underlying generalizations are defined over unobservables, and they lead to its predictions by iterating and interacting rather than by being directly instantiated. (1987: 7) As these passages make clear, Fodor’s account of commonsense psychology posits an implicit, sciencelike theory featuring generalizations over unob-servables (in this case, mental states). People are said to arrive at common-sense mental attributions by using the theory to guide their inferences.
Where does our naı¨ve psychological theory come from? Fodor addresses this in his epilogue:
Here is what I would have done if I had been faced with this problem in de-signing Homo sapiens. I would have made a knowledge of commonsense Homo sapiens psychology innate; that way nobody would have to spend time learning it.. . . The empirical evidence that God did it the way I would have isn’t, in fact, unimpressive.. . . There is, so far as I know, no human group that doesn’t explain behavior by imputing beliefs and desires to the behavior.. . . At least in our culture, much of the apparatus of mentalistic explanation is apparently operative quite early. (1987: 132)
In a subsequent paper on the child’s theory of mind, Fodor elaborates his nativist, modularist, theory-theorist hypothesis. In discussing false-belief phenomena, he says that 3-year-olds and 4-year-olds share the same ‘‘primi-tive theory’’ (1987: 285) and offers an account of the changes between 3- and 4-year-olds that he regards as ‘‘compatible with. . . an extreme Cartesianism, according to which intentional folk psychology is, essentially, an innate, modularized database’’ (1987: 284).
Leslie’s approach is very similar. Here is a position statement from the same period that includes the theorizing feature:
We believe that having access to such data structures [namely, three-place rela-tional structures involving an agent slot, an anchor slot, and a proposition slot], together with the system of inferences they support, constitutes a tacit and intuitive theory of mind, or, if you like constitutes a theory of the specific ‘‘representational relations’’ (like pretends, believes, wants) that enter into the causation of agents’
behavior. (Leslie and Roth 1993: 91, emphasis added)
Elsewhere Leslie and German again highlight a commitment to theory-theory:
‘‘We make no bones about the fact that we are on the side of theory-theory and that we are skeptical about at least radical simulationism’’ (Leslie and Ger-man, 1995: 123).
There are other places in Leslie’s writing, however, especially recent writings, where the ‘‘TT’’ label is spurned. For example, ‘‘here I shall confine myself to examining the deeper motivations for theory-theory in order to say why I believe the entire enterprise is mistaken’’ (Leslie, 2000: 198). Such disavowals of the ‘‘TT’’ label, I suspect, do not constitute a major change in
his position. Instead, they emphasize a point on which he has always taken issue with child-scientist theorists. This concerns acquisition of the implicit, intuitive theory. Leslie takes strong exception to the notion that the theory is acquired in the same way that adult scientists acquire their theories (whatever way that may be). This component of paradigm TT, then, Leslie does not embrace (on ‘‘paradigm’’ TT, see section 2.1). So he isn’t a paradigm theory-theorist, but I would count him as a kind of theory-theorist nonetheless.
Leslie’s maneuvers to distance himself from the child-scientist position sometimes take a slightly odd form. For example, he claims that children have only ‘‘theory-like’’ knowledge structures, not ‘‘real’’ theories of the sort scientists have (Leslie, 2000). What is the difference between a ‘‘real’’ theory as opposed to mere ‘‘theory-like’’ knowledge? It sometimes seems to reside, for Leslie, in the difference between explicit versus implicit knowledge:
explicit in the case of scientists, implicit in the case of children. But isn’t the theory-theory position usually explained in terms of an implicit theory? That is certainly the language used by Fodor and often Leslie himself. Why can’t implicit knowledge of a theory still be knowledge of a real theory rather than something merely theorylike (whatever the latter difference is)?
Another way Leslie sometimes distances himself from TT is in his depiction of children’s grasp of mental-state concepts. Leslie, Friedman, and German (2004) reject the child-scientist idea that ‘‘we are born as ‘little scientists’
who discover belief and desire through experimentation, observation and theory-building’’ (p. 528). But Leslie et al. still depict desires and beliefs as theoretical entities—‘‘abstract’’ entities, in their terminology—on a par with electrons and genes. They contrast the concepts of belief and desire with the concepts of electron and gene insofar as the former are innate and the latter aren’t. But their insistence on the ‘‘abstractness’’ of desire and belief bears testimony to the continuing hold of the theorizing theme, in which the posited states are unobservable in the manner of classical scientific theorizing.
Like Fodor, Leslie does not maintain that users of naı¨ve psychology merely possess a theory; he holds that they deploy that theory to make inferences leading to mental-state attributions. Invocation of theory-guided inference appears in the previously quoted passage from Leslie and Roth (1993), which speaks of the ‘‘system of inferences’’ that the proprietary data structures of the theory support. Talk of inference—presumably, theory-guided inference—
can also be found in this passage describing mental attributions:
These results support a number of features of the metarepresentational model of pretence. They demonstrate counterfactual causal reasoning in 2-year-olds based on imaginary suppositions. For example, in the CUP EMPTY/FULL scenario the child works from the supposition the empty cups ‘‘they contain juice’’ and upon seeing the experimenter upturn one of the cups, the child applies a ‘‘real world’’ inference concerning the upturning of cups.. . . In the experiment, the children correctly inferred what the experimenter was pretending. The very
possibility of ‘‘correctness’’ depends upon some definite pretend situation being communicated. The child calculates a construal of the agent’s behavior—a construal which relates the agent to the imaginary situation. The child is not simply socially excited into producing otherwise solitary pretend; the child can answer questions by making definite inferences about a definite imaginary situ-ation communicated to him by the behavior of the agent. (Leslie, 1994: 224–225;
emphasis added)
The phrasing here refers repeatedly to the child’s ‘‘causal reasoning,’’ ‘‘in-ferences,’’ and ‘‘calculations,’’ reinforcing the inferentialist and hence theo-rizing nature of the model. The commitment to TT is further elaborated in the following passage:
On the other hand, you may ask, why call a [mentalizing mechanism] a ‘‘theory-theory’’? The minimal answer is that, as we saw in the case of language, systems of representation themselves constitute bodies of knowledge. To fully deploy such systems, additional abilities are required (e.g., inferencing that is sensitive to the structure of the representations). For this entirely general reason, theory-theories embrace both knowledge and ability. (Leslie and German, 1995: 128) On the question of modularism, Leslie’s position departs a bit from Fodor’s in rejecting thoroughgoing modularism. His position is best characterized as semimodularist. It begins by postulating the ‘‘theory of mind’’ mechanism (ToMM), regarded as part of the core architecture of the human brain. ToMM is specialized for learning about mental states. It kick-starts belief-desire at-tribution, but effective reasoning about belief contents also depends on a process of content selection by inhibition. This process is executed by the selection processor (SP), a second mechanism that develops slowly through the preschool period and beyond and is not regarded as modular.