Ian Pitchford on brain plasticity, April 23, 1999:

I think we should be careful not to conflate two very different propositions: (a) complex functions result from brain plasticity (true) and (b) complex functions result only from brain plasticity (false). Models based on parallel distributed processing and evolutionary theory both have much to say about human psychological functions, and I see them as complementary approaches.

The idea of domain-specificity, which has become part of evolutionary psychology over the last 10-15 years, has been central to neuroscience and neurology for a century and a half, and has its origins in a paper read by Marc Dax in Montpellier in 1836 detailing "a series of clinical cases demonstrating that disorders of speech were constantly associated with lesions of the left hemisphere." In order to have any reasonable chance of predicting the consequences of a lesion the first question any neurologist wants answered is "which brain structures are involved?" Some modules, such as the thalamo-amygdala circuits involved in fear conditioning, play such a key role survival that they have been conserved for tens of millions of years. According to a paper I came across recently, in terms of volume the centromedial nucleus of the amygdala is the only brain structure in primates to correlate with life-span (Allman, 1993). In very general terms it's legitimate to claim that neuroscience validates the concept of domain-specific functions that has become a tenet of evolutionary psychology.

Those who are relying on computational associationism to disprove innateness and domain specificity seem to be relying on an implausible principle that Richard Samuels has dubbed the "Principle of Invariance":

"The innately specified (representational) properties of a piece of cortical tissue T are invariant under alterations in T's location within the brain and a lterations in the afferent inputs to T"

Evolutionary psychologists don't subscribe to this "tissue nativism", but to a version of representational nativism better described as "organism nativism" or "genomic nativism" - as Samuels concludes:

"... the neurobiological argument fails to undermine RN [representational nativism] because it makes a series of unwarranted assumptions about nativism and about the extent to which neurobiological data constrain claims about the innateness of mental representations. Pace Elman et al., the innately specified properties of a piece of cortical tissue need not be intrinsic properties of the tissue, nor must they satisfy the Principle of Invariance. Moreover, even if we were to assume that the innate properties of neural tissue must satisfy both of these conditions, the neurobiological argument would still fail to undermine the version of RN that psychologists actually defend - it would only provide us with reason to reject tissue nativism and not organism nativism."

Finally, it's also important to remember that there are clear limits on brain plasticity - I'm told there is a good discussion of what does, and what does not, recover after brain damage in Kolb (1995).



Allman, J. M., McLaughlin, T., & Hakeem, A. (1993). Brain structures and life-span in primate species. Proceedings of the National Academy of Sciences of the United States of America, 90(8), 3559-63.

Kolb, B. (1995). Brain plasticity and behaviour. Mahwah, NJ: Lawrence Erlbaum.

Elman, J. L., Bates, E., Johnson, M. H., Karmiloff-Smith, A., Parisi, D., & Plunkett, K. (1996). Rethinking innateness: a connectionist perspective on development. Cambridge, MA: MIT Press.

Samuels, R. (1998). What brains won't tell us about the mind: a critique of the neurobiological argument against representational nativism. Mind and Language, 13(4), 548-570.

Ian Pitchford <Ian.Pitchford@scientist.com>
Centre for Psychotherapeutic Studies
Department of Psychiatry
University of Sheffield, S10 2TA, UK