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“Neural reuse” refers to the exaptation of established and relatively fixed neural circuits without loss of original function/use. Reuse arises over the course of normal development and evolution. The evidence of this phenomenon speaks most loudly against the idea of strict domain-specificity. It seems that no area of the brain is exempt from redeployment, with areas of the brain traditionally considered to be among the most domain-specific (such as sensory areas) also contributing their computational/structural resources to other domains, including those involving language. The evidence supporting reuse takes many forms, among them evolutionary and developmental considerations, computational considerations, and the neuroimaging and biobehavioral literature.

The previous chapter argued that we ought to regard dissociability as the sine qua non of modularity. As for what in the brain meets this standard of modularity, the only likely candidate will be something resembling a cortical column. But this is not guaranteed. The effects of the neural network context may so compromise a region’s ability to maintain a set of stable input–output relations that it cannot be considered a genuine module. The brain’s network structure poses particular difficulties for modularity, since even if we were to treat nodes as modules, still we could be missing the point—the key to networks lies not in their nodes, but in the structure of their interactions, and these interactions make pinning down what any single node “does” a fraught enterprise. The chapter includes a table of specificity for brain regions.

There seems to be no language module, no elementary linguistic unit, no hardwired language organ. Language was probably assembled from older sensory-motor and nonlinguistic materials. Neuroimaging, biobehavioral, computational, and evolutionary considerations all point to the same conclusion. Such linguistic adaptations as there have been have been coopted in many other domains of cognition. The sort of cultural environment in which language exists is too unstable to provide the conditions for typical selection scenarios in which robust phenotypes can emerge, and the brain anyway negotiates energetic constraints by repurposing existing resources to meet new challenges. Language acquisition frequently does seem effortless on the child’s part, and exhibits a degree of developmental robustness. But the ease of acquisition has probably been exaggerated, and the child’s environment is not so impoverished as was once assumed. In any case, such ease of acquisition can be explained other than by postulating exotic and impossible-to-evolve circuitry. Language has been shaped by the brain far more than the brain has been shaped by language. Cultural evolution is a powerful factor in human history, and is more than sufficient to explain why languages seem to run so well with the grain of the human mind. It is true that language dissociates from other cognitive skills, at least in some respects, but the Redundancy Model puts this sort of modularization in its proper context.