11/01/2006

Innate But Domain-General Mechanisms?

As mentioned in yesterday's post, cognitive studies of language tend to address two inter-related debates: the extent to which language relies on domain-general vs. domain-specific mechanisms, and the extent to which language relies on innate vs. learned mechanisms. To demonstrate that these are distinct debates, we need to demonstrate that a position on one debate does not dictate your position on the other.

Perhaps the strongest challenge to the claim that these are distinct debates comes from the fact that it is relatively difficult to find theorists who advocate domain-general but innate mechanisms. After all, what domain-general and yet completely innate mechanism could possibly enable language?

One possible answer is recursion. Some have argued that recursion is the only aspect of language which is unique to humans (Hauser, Chomsky & Fitch, 2002) but this is not domain-specific – as Spelke (2003) suggests, such “combinatorial” capacity could also underlie other uniquely human achievements like cooking, mathematics, and music. Therefore, at least two outspoken advocates of nativism have proposed an innate but domain-general mechanism.

Another DG mechanism thought by some to be responsible for language is theory of mind (ToM). Despite extensive training, chimpanzees have not demonstrated human-level performance on all ToM tasks (Tomasello et al., 2003), leading some to suggest that it may be a uniquely human adaptation (and thus in some sense innate). Although language and ToM performance are correlated, the capacity to understand the minds and intentions of others is not language-specific. Therefore, this view also advocates a domain-general but innate mechanism.

Note: This post is part 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 need not be learned (coming soon)
Part III: Some domain-specific mechanisms need not be innate (coming soon)
Part IV: Dissociations from data and conclusions (coming soon)

References:

Hauser MD, Chomsky N, & Fitch WT. (2002) The faculty of language: what is it, who has it, and how did it evolve? Science. 2002 Nov 22;298(5598):1565-6.

Spelke, E., 2003. What Makes Us Smart? Core Knowledge and Natural Language. In: Gentner, D. & Goldin-Meadow, S., Language in Mind: Advances in the Study of Language and Thought. Bradford Books/MIT Press, Cambridge, MA.

Tomasello M, Call J, & Hare B. (2003). Chimpanzees understand psychological states - the question is which ones and to what extent.

5 Comments:

Blogger Rick Thomas said...

Deacon argues for this position. This paper (pdf) outlines the argument, though without the neuroscience details of his book. Basically, there was a symbolic constraint in addition to neurological and cultural constraints under which language and the brain co-evolved. Language did most of the evolving to be learnable by young human brains, but brains also evolved, adapting general structures for symbolic use. This is akin to the recursion idea.

11/01/2006 09:09:00 AM  
Anonymous Tad said...

I'm a little confused why ToM counts as innate and domain general. Isn't social cognition a domain? A lot turns on how domains are individuated - a very deep problem.

In any case, some (Pinker) have proposed that ToM and recursion might actually be connected. After all, the ascription of mental states can show indefinite embedding, e.g., He knows that she think that he wants that she ignore.... This may have been selected for as the result of 'arms race' dynamics involving deception and deception detection.

But Pinker takes this to show, I think, that recursion arose in a specific domain (social cognition), and then may have been coopted to language which, after all, must be closely related to social cognition, given its use in communication.

So I'm not sure where this leaves us. The examples seem to be compatible with the hypothesis that language is part of a broader theory of mind / communication domain, and that this domain requires recursive capacity. Is that sufficient for domain generality?

Again, it depends on how you parse domains. Perhaps some domains that we intuitively distinguish aren't really distinct, so, e.g., language is part of social cognition. But that doesn't mean that there are no 'real' cognitive domains with dedicated, innate resources. Social cognition might be one. In order to truly find an example of a domain general, innate capacity, shouldn't we be looking for something innate, that arguably can be applied to any domain, like associationist learning can?

11/01/2006 10:56:00 AM  
Blogger Chris Chatham said...

Wow, two excellent comments in one morning.

Rick: thanks for pointing me towards Deacon (again?) I'm going to be in a reading group about the evolution of symbols soon, so I will be recommending something from Deacon.

Tad: You bring up an excellent point that I have not confronted whatsoever (admittedly a big problem): how do you define your domains? It's a difficult issue and one that I can't resolve, and one that I'm afraid might degrade into semantics at some point.

To make a feeble attempt, I'd claim that ToM and recursion are both domain-general because there does not seem to be a single ToM or "recursion" module in the brain, and because both apply in a variety of settings (for example, kids without a ToM can even make mistakes about their own previous beliefs, so it's not necessarily social cognition).

Anyway, I agree that the most productive way forward is to see how far association learning can take us... Hopefully I didn't misunderstand your points.

11/01/2006 11:04:00 AM  
Anonymous Torbjörn Larsson said...

This seems like a good blog when a layman like me wants an orientation in some neuroscience. I like the comprehensive posts and especially this type that separates out confusing conflations.

BTW, one argument that I didn't see here supporting recursivity as a domain-general mechanism, perhaps because it is a common argument, is that it seems hard to avoid. (Of course, Deacon mentions it under "topological universals".) Symbolic math may or may not have it, but parts like realised algorithmic constructions certainly have. Practical, efficient computers and their languages are Turing complete, and of course recursivity is among the few simple requirements. So one finds it in diverse systems. (I find it awesome that famously even Conway's simple Game of Life cellular automata can be set up to be so. http://www.cs.ualberta.ca/~bulitko/F02/papers/tm_words.pdf )

11/01/2006 04:36:00 PM  
Blogger Chris Chatham said...

Hi Torbjörn - I'm glad you enjoy the blog! Thanks for the comment, I'm a big fan of cellular automata.

Rumor has it that David Olmstead (of neurocomputing.org) is working on a "continuous cellular automata" form of neural network modeling. I'm not sure exactly what that means, but he'll have a paper coming out soon in one of the PLoS science journals.

11/01/2006 06:01:00 PM  

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