The Evolutionary Psychology FAQ

Edward H. Hagen, Institute for Theoretical Biology, Berlin

What is a module?

A module is a psychological adaptation (see above). Note that this usage of the term 'module' differs from several of the definitions of 'module' used by cognitive psychologists. For those familiar with the 'modularity' debate, I will make one brief comment: Fodor distinguishes between cognitive modularity with, and without, information encapsulation (Fodor 2000, p. 56-58). If, when performing the computations, modules only have access to information stored in the module itself, and cannot access information in other modules, the module is said to be informationally encapsulated. As a concept, information encapsulation is so unhelpful that one wonders whether its importation from computer science into cognitive science was botched. Why, except when processing speed or perhaps robustness is exceptionally important, should modules not have access to data in other modules? Most modules should communicate readily with numerous (though by no means all) other modules when performing their functions, including querying the databases of select modules.

The original computer science concept of encapsulation, in contrast, is powerful: encapsulated modules access and modify data in numerous other modules when performing their functions, but only do so via well-defined interfaces. This means, roughly, that modules communicate in standardized ways, and that access to a module’s data and functionality is regulated by the module itself. As long as the interface between modules stays the same, programmers can tinker with modules’ implementations without disrupting other modules. In computer science, it is a module’s functionality that is encapsulated, not its data per se. (The standardized way in which nerve cells communicate is a low-level example of encapsulation in the brain. Whether natural selection could have evolved this useful architecture at higher, neural network levels in the brain is an open question, but it would clearly allow individual modules to evolve without interfering with other modules.)

Copyright 1999-2002 Edward H. Hagen