BBS Commentary on Susan Carey , The Origin of Concepts Acquiring a new concept is not explicable - by - content

Carey’s book describes many cases where children develop new concepts with expressive power that could not be constructed out of their input. How does she side-step Fodor’s paradox of radical concept nativism? I suggest it is by rejecting the tacit assumption that psychology can only explain concept acquisition when it occurs by rational inference or other transitions that are explicable-by-content. Main text Representational explanation is central to psychology. Mental processes are characterised in terms of causal transitions between token states, where we make sense of the transitions in terms of the content of the states. Can we explain concept acquisition in the same way? Only insofar as the acquired concept is constructed out of pre-existing concepts, according to Fodor. Since most lexical concepts do not seem to be so-constructed, Fodor concludes that they are innate – their acquisition is outside the ambit of psychological explanation. Carey’s book is a comprehensive refutation of radical concept nativism, offering many psychological explanations of concept acquisition, and the data to back them up. How, then, does Carey side-step Fodor’s argument? I want to suggest that she has to reject the assumption that all psychological explanations are explanations-in-virtue-of-content. Consider two of the stages in Carey’s account of the acquisition of number concepts. First, the transition from parallel individuation to enriched parallel individuation (being a one-knower, two-knower, etc.). Numerosity is not represented explicitly anywhere in the parallel individuation system. It is implicit in the various operations that are performed on object files: adding, subtracting and comparing by 1-1 correspondence. The child then comes to associate words with object files of a certain size, e.g. “one” with having one object file of any kind open: {i}. Is this step explicable-by-content? Before becoming a one-knower, the child was not representing one-ness explicitly at all: “one” was just a sound, and numerosity was merely implicit in the object file system. The child did not have resources out of which a hypothesis about one-ness could be constructed. But there were two important correlations that they could make use of: (1) between having one object file {i} open and singleton sets; and (2) between the word “one” and singleton sets (the mechanism for which involves the child’s linguistic community). Although neither is a representation of one-ness, these are two pieces of information, of the purely correlational type (e.g. Shannon information). Since the two mental items correlate with the same externalworld property, they tend to occur together, so become associated. The association between