Wednesday, March 25, 2015

What evolves? evo-psych and the logic of traits and capacities

I just read an interesting paper by Mark Fedyk on evolutionary psychology (EP) (here). The paper does a pair of things (i) it provides an accessible discussion of the logic behind EP and (ii) it criticizes the massive modularity hypothesis (i.e. the proposal that minds/brains consists of many domain specific modules shaped by the environmental exigencies of the Pleistocene Epoch).[1] 

Fedyk elucidates the logic of EP by discussing the relation between “ultimate” and “proximate” explanations. The former “refer to the historical conditions responsible for causally stabilizing a particular phenotype (or range of phenotypes) in a population” (3). Such explanations try to isolate “why a pattern of behavior was adaptive in an environment” however it is not restricted to the mechanisms involved in fitting the phenotype with the environment. These mechanisms are the province of “proximate” explanations. These refer to the “psychological, physiological, neurophysiological, biochemical, biophysical, etc. processes which occur at some point within the course of an organism’s development and which are responsible for determining some aspect of an organism’s phenotype” (3).

One of Fedyk’s main points is that there is a many-many relation between ultimate and proximate explanations and, importantly, that “knowing the correct ultimate explanation” need “provide no insight whatsoever” into which particular proximate explanation is correct. And this is a problem for the EP research program which aims to “offer a method for discovering human psychological traits” (Fedyk quoting Machery)(5). Here’s how Fedyk summarizes the heuristic (6):

…the evolutionary psychologist begins by finding a pattern of human behavior that in the EEA [environment of evolutionary adaptedness, NH] should have been favored by selection. This is sufficient to show that the patterns of behavior could have been an adaptation…Next, the evolutionary psychologist infers that there is a psychological mechanism which is largely innate and non-malleable, and which has the unique computational function of producing the relevant pattern of behavior. Finally a test for this mechanism is performed.

The first part of the paper argues that this logic is likely to fail given the many-many relationship between ultimate and proximate accounts.

In the second part of the paper, Fedyk considers a way of salvaging this flawed logic and concludes that it won’t work. I leave the details to you. What I found interesting is the discussion of how modern evolutionary differs from the “more traditional neo-Darwinian picture.” The difference seems to revolve on how to conceive of development. The traditional story seemed to find little room for development save as the mechanism for (more or less) directly expressing a trait. The modern view understands development to be very environment sensitive capable of expressing many traits, only some of which are realized in a particular environmental setting (i.e. many of which are not so realized and may never be). Thus, an important difference between the traditional and the modern view concerns the relation between a trait and the capacities that express that trait. Traits and capacities are very closely tied on the traditional view, but can be quite remote on the modern conception.

Fedyk discusses all of this using language that I found misleading. For example, he runs together ‘innate,’ ‘hardwired’ and ‘malleable.’ What he seems to need, IMO, is the distinction between traits and the capacities that they live on. His important observation is that the traits are expressions of more general capacities and so seeing how the former change may not tell you much about how (or even whether) the latter do. It is only if you assume that traits are pretty direct reflections of the underlying capacities ( i.e. as Fedyk puts it (15): if you assume that “each of these modules is largely hardwired with specific programs which must cause specific behavioral patterns in response to specific environmental conditions…”) that you get a lever from traits to psychological mechanisms.

None of this should strike a linguist as controversial. For example, we regularly distinguish a person’s grammatical capacities from the actual linguistic utterances produced. Gs are not corpora or (statistical) summaries of corpora. Similary, UG is not a (statistical) summary of properties of Gs. Gs are capacities that are expressed in utterances and other forms of behavior. UG is a capacity whose properties delimit the class of Gs. In both cases there is a considerable distance between what you “see” and the capacity that underlies what you “see.” The modern conception of evolution that Fedyk outlines is quite congenial to this picture. Both understand that the name of the game is to find and describe these capacities, and that traits/behavior are clues, but ones that must be treated gingerly.

[1] One of the best reads on this topic to my mind is Fodor’s review here.

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