Setting the Scene

The modularity of mind has been understood in various ways, amended as evidence from neuroscience has forced the theory to shed various structural assumptions. Neuroplasticity has, for better or worse, challenged many of the orthodox conceptions of the mind that originally led cognitive scientists to postulate mental modules. Similarly, rapidly accumulating neuroscientific evidence of the reuse or redeployment of neural circuits, revealing the integrated and interactive structure of brain regions, has upset basic assumptions about the relationship of function to structure upon which modularity—not to say neuroscience itself—originally depended. These movements, developments, and cross-currents are the subject of this book. This chapter outlines the basic argument of the book and its motivation.

The Language Module Reconsidered

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.

Neural Reuse and Recycling

“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.

Modules Reconsidered

In recent decades, neuroscience has challenged the orthodox account of the modular mind. One way of meeting this challenge has been to go for increasingly “soft” versions of modularity, and one version in particular, the “system” view, is so soft that it promises to meet practically any challenge neuroscience can throw at it. But an account of the mind that tells us that the mind can do different things, even interesting things, is not itself necessarily an interesting account. This chapter considers afresh what ought to be regarded as the sine qua non of modularity, and offers a few arguments against the view that an insipid “system” module could be the legitimate successor of the traditional notion.

Saving Faculty Psychology

The future of faculty psychology depends in no small part on the productive collaboration between neuroscience and psychology. The argument from multiple realization has posed a significant philosophical stumbling block to this quest in the past. Multiple realization should not be taken as an empirical given—establishing that a kind is multiply realizable takes a good deal of work, as Shapiro has been at pains to show; and even when the existence of an MR kind can be verified, the details of its implementation do not suddenly become irrelevant. Structure and function are two sides of the same coin. Thus the multiple realization argument provides no basis for neglecting the discoveries of neuroscience. Faculty psychology’s strength lies precisely in its willingness to work with neuroscience.

Are Modules Innate?

It should by now be clear that modules are sensitive with respect to such experiences as learning, injury, and sensory deprivation, regardless of how young or mature the organism happens to be. And yet this is not the full story. The brain’s plasticity is definitely constrained. While plasticity is an intrinsic and crucial feature of the nervous system, it is important to emphasize that the brain is not open-endedly plastic. Furthermore, a brain region can be innate in a relatively strong sense and yet fail to reach the threshold characteristics of a genuine module. A bias, after all, is not a specialization.

Modules Reconsidered

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.

Aspects of Neuroplasticity

The brain exhibits an impressive degree of plasticity, even as it ages. Plasticity is really an intrinsic feature of the nervous system, not an exceptional or occasional state. Neuroplasticity comprises a family of different types of plasticity. Of these, synaptic plasticity is perhaps the best-understood variety, and it plays an important role in cortical map reorganization and memory consolidation. Cortical map plasticity is of direct relevance to any discussion of modularity. There are two types of cortical map plasticity: intramodal (within a modality) and crossmodal. Crossmodal plasticity is likely to arise from the underlying supramodal (or “metamodal”) organization of the brain.

Summing Up

No one denies the brain’s intricacy of structure and function. The debate has always been over what form this complexity takes. The most influential answer to this question for over 60 years—and the most controversial for almost 40—is that the mind is composed of modules. This book offers a clearer, cleaner and far more realistic picture of what that means. It is respectful of advances in psychology and philosophy over the past half century, but is anchored firmly in the neurobiological evidence. It attempts to strike an ideal balance between different approaches to the investigation of the mind/brain.