Developmental Disorders and Cognitive Architecture

The dissociations that result from developmental psychopathologies (Down syndrome, etc.) have been one of the main sources of evidence for breaking up the mind into pieces – that is, for identifying the components of the typical cognitive architecture. But is this practice justified? Do these dissociations really provide evidence about the components of our cognitive architecture? 

Neuropsychologist Annette Karmiloff-Smith argues that developmental psychopathologies provide no evidence about the components of our cognitive architecture. In a new paper, I argue that they do.
What do you think? 
(Comments on the paper welcome, as usual!)


  1. Josh Weisberg


    Very interesting paper–I liked it very much.

    One question concerning your quick rejection of K-S’s developmental holism claim. Might she respond that biological modularity can reasonably be doubted in the brain because of its unique complexity and arrangement? Of course, that’s just hand-waving to some extent, but I wonder if the hypothesis of neural Darwinism might help her. The use-it-or-lose-it, fire-together wire-together features of brain development on this view (as I understand it) seem different from the usual trait shielding modularism. This is just a hunch, but I wonder what you might think of it.

    Also, I wonder about plasticity and holisitic development. If a process does not develop in a normal anatomical way–that is, if it fails to get the right input hookups–the brain region normally underwriting that process can be co-opted by some nearby process. You then get some weird effects (phantom limbs felt on faces, Broca’s area used visuo-spatial processing in ALS). Here, perhaps, you damage one thing and the residual processing is oddly altered. More holism?

    These are really more queries than objections, but I thought that bit in the paper went by pretty quick!


  2. edouard machery


    Thanks for these great points.
    First, I agree with you that there is more to be said about the nature of brain development than I say in the paper. I did not think (and still do not think it was necessary to say more in the paper, however. For KS, the considerations about brain development are at best a plausibility argument; her argument really relies on her empirical findings and interpretations thereof.
    Still, the substance of your question should be addressed. 
    Neural Darwinism. Although the phenomenon is a fact, I doubt that it is pervasive and that it explains numerous properties of the brain, particularly the large-scale properties of the brain. 
    Plasticity. This is an interesting idea. But note that plasticity seems to show that cognitive development is not holistic, but rather is robust and shielded against at least some brain injuries. Plasticity shows that a normal cognitive system can develop in spite of neural abnormalities. The developmental system for cognition thus seems to be robust: To some extent, injuries to some brain areas do not prevent a normal cognitive development. (Quasi-normal would be better than normal, since the systems that develop inn abnormal brain areas typically have sui generis information processing properties.) This would seem to count against KS’s views that any brain injury will lead to a very very different cognitive architecture.
    Also, Richard Samuels wrote an excellent paper where he argues that plasticity does not undermine the massive modularity hypothesis: Samuels, R. (1998). What brains won’t tell us about the mind: A critique of the neurobiological argument against representational nativism. Mind & Language, 13(4), 548-570.. I agree with most of what he says there.

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