Gall’s Legacy Revisited: Decomposition and Localization in Cognitive Neuroscience

The standard philosophical account of explanation—the deductive nomological model in which a phenomenon is explained when a description of it is derived from statements of laws and initial conditions—does not do justice to the explanations generally offered in the life sciences. There, instead, explanations often take the form of specifications of mechanisms, wherein an overall activity of a system is decomposed into sub-functions and these are then localized to components of the system (Bechtel and Richardson, 1993; Machamer, Darden, and Craver, 2000). Mental activities have been no exception. The brain (including the central nervous system) has long been taken to be the bodily organ responsible for mental activities, and the task has been to decompose mental functions and identify the resulting component functions with parts of the brain. In many respects, this effort embodies the vision of Franz Joseph Gall. Modern cognitive neuroscience, the most sophisticated attempt yet to link mental functions with neural structures, has embraced the quest for mechanistic explanation through decomposition and localization (Bechtel, 2000). Thus, part of the legacy of Gall is very much still alive. However, there are different strands in this legacy. Part of our goal is to differentiate three of these strands. One, which we link with Fodor’s proposal for modularity, follows Gall himself in seeking direct neural instantiation of whole mental functions such as language (or at least syntactic processing). The second and third strands both go beyond Gall in decomposing individual mental activities into component processes. It is then component processes at some level in the decomposition that are linked to brain structures. The second strand, prevalent in philosophical accounts of mind-brain relations and in psychological research which is cut of