11/03/2006

Disentangling Two Debates: Conclusions

In the last few posts, I established that the debate about domain-general vs. domain-specific mechanisms is theoretically orthogonal to the debate about whether those mechanisms are innate or learned. Here, I've attempted to illustrate how these debates are typically confounded in many studies of the development of language.

Despite the stereotype that nativists advocate domain-specific (DS) mechanisms and that empiricists advocate domain-general (DG) mechanisms, the evidence above clearly establishes that nativist/empiricist debates can be considered orthogonal to the DS/DG debate. Some empiricists can be seen to argue for DS mechanisms (at least at the end-state of learning), while some nativists advocate the DG mechanism of recursion. The assumption that issues of nativism necessarily bear on the DS/DG debate is thus frequently mistaken.

Unfortunately, this faulty assumption is frequently made in the literature, in that evidence bearing on just one of these two distinct debates is frequently interpreted as bearing on both. For example, evidence on the use of the “one-to-one principle” from the isolated deaf and from speakers of Kannada is interpreted to suggest that “domain-specific grammatical knowledge guides linguistic development” (Lidz & Gleitman, 2004) when in fact no evidence is presented that the “one-to-one principle” is reflected only in linguistic tasks. In this case, the researchers have confounded the question of innateness with that of domain-specificity, and assumed that evidence bearing on innateness (e.g., the use of the one-to-one principle in home sign-language, and among speakers of a language whose grammar does not obey the one-to-one principle) also bears on domain-specificity (e.g., whether the “one-to-one” principle is specific to language or whether it actually reflects cognition in general).

Confounding these two distinct debates is not limited to the nativists, however. For example, the fact that children’s usage of syntax appears to be usage-based rather than reflective of an innate grammar has been interpreted as evidence that “general cognitive and social skills” are used in the process of generalization (Tomasello, 2000). This conclusion is wholly unwarranted, because it is clearly possible that language-specific skills (such as analogy, which Tomasello explicitly mentions) are involved in the generalization process.

In a similar fashion, the Latent Semantic Analysis framework establishes that semantic learning need not be enabled by strong instinctive word-learning biases, but can instead occur through statistical learning (Landauer & Dumais, 1997). However, the authors speculate that similar algorithms may actually underlie “associative learning theory” without demonstrating that this is actually the case in any domain except for linguistic or symbolic tasks. Here again, evidence bearing on the innateness question is interpreted to bear on the domain-specificity debate, without acknowledging that these debates are distinct and without mustering evidence that conclusively demonstrates domain-generality.

Likewise, evidence that bears only on the domain-specificity debate is frequently misinterpreted as bearing on the innateness debate. For example, some patients show selective deficits in knowledge for living and non-living things (apparently demonstrating domain-specificity for these categories). This has been hastily interpreted as demonstrating that the neural representation of these categories may be innately specified (Zaitchik & Solomon, 2001). Another study demonstrated selective deficits for living things in a patient who sustained brain damage at 1 day of age, and interpreted this as evidence that a “living things” module is genetically specified (Farah & Rabinowitz, 2003). However, the damage could have been localized to a more DG process, such as retrieval by visual associations, which would differentially impact knowledge of living things.

After a cursory review of the literature on language, it would be easy to think that nativists advocate innate DS mechanisms for language, and that empiricists advocate DG statistical learning mechanisms. However, this is an overly simplistic view; it is contradicted by examples of nativists arguing that language is enabled by a particular innate and yet DG mechanism, and also by other examples where language learning is subserved by statistical learning processes that are (or become) specific to language. Unfortunately, this simplistic view of these two debates is further reinforced by research where evidence on innateness is interpreted in the context of domain-specificity, and vice versa. It will be important for psycholinguists to acknowledge the independence of these debates rather than further confound them.

Note: This is the final post of a series on how to disentangle the domain-specificity debate from the nativism debate in cognitive studies of language.
Part I: Disentangling Two Debates: Introduction
Part II: Some domain-general mechanisms may be innate
Part III: Some domain-specific mechanisms need not be innate

References:

Farah, M.J. & Rabinowitz, C. (2003). Genetic and environmental influences on the organization of semantic memory in the brain: Is “living things” an innate category? Cognitive Neuropsychology, 20, 401-408.

Landauer, T. K. & Dumais, S. T. (1997) A solution to Plato’s problem: The Latent Semantic Analysis theory of acquisition, induction, and representation of knowledge. Psychological Review 104:211–40.

Lidz J, & Gleitman LR. 2004. Argument structure and the child's contribution to language learning. Trends Cogn Sci. 2004 Apr;8(4):157-61.

Tomasello M. (2000). The item-based nature of children's early syntactic development. Trends Cogn Sci. 2000 Apr;4(4):156-163.

Zaitchik, D., & Solomoon, G.E. (2001). Putting semantics back into the semantic representation of living things. Behavioral and Brain Sciences (2001), 24: 496-497

2 Comments:

Anonymous olivier said...

I agree on the overall point: innateness does not entail domain-specificity and vice-versa.

I would be less severe than you are about the innateness of naive biological categories: the works you cite are indeed uncautious, yet they also rely on a huge body of evidence in developmental psychology of concepts and in the cognitive anthropology of biological lore. Some regularities in the way children and people all over the world conceive of living things seem difficult to explain without assuming some information not borne by the stimuli.

But I know that my case is weak, as are all cases depending on a poverty-of-the-stimulus argument. Anyway, you were right to limit the conclusions of Farah and others.

11/03/2006 10:04:00 AM  
Blogger Chris Chatham said...

Thanks for your comment - point well taken :)

11/03/2006 10:59:00 AM  

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