Duplications and Domain-Generality

Although specialized, adaptive behavioral traits are ubiquitous in the animal kingdom. at least in humans, there are considerable debates on whether the mind is primarily characterized by various special-purpose. domain-specific mechanisms or by a few general-purpose, domain-general mechanisms. Drawing from research on artificial language learning, associative learning, serial learning, executive control, and formal linguistics, I argue that neither domain-specificity nor domain-generality provide satisfactory descriptions when considering how cognitive mechanisms are implemented. I suggest that some cognitive mechanisms are domain-bound-they are available in multiple domains (and thus not domain-specific), but not in other domains (and thus not domain-general). Hence, these computations can be performed in many domains but not in others, can be recruited simultaneously by multiple domains, and, across domains, individual abilities with a given computation are relatively uncorrelated. Domain-bound mechanisms have a straightforward evolutionary interpretation: Analogously to the evolution of molecular and morphological structures, cognitive mechanisms can become duplicated over evolution, with independent copies in different domains. This and previous evidence for the importance of duplications for our cognitive abilities call for a revision of the concept domain-generality, suggesting that, in many cases, mechanisms traditionally seen as domain-general might really reflect a collection of local copies of specialized mechanisms.