Introduction

The study of domain specificity is the study of the fit between the properties of information processing systems and the properties of information that they process. Critical to this enterprise is the fact that information processing systems do not process information randomly. This gives rise to an inevitable relationship: every information processing system does something systematic with information, and that, in turn, delineates a domain. The question of what kind of information a system operates on therefore depends critically on what it does with that information, which in turn depends on its function. This is a version of the idea of “form-function fit” in biology, applied specifically to the realm of information processing, and it is the central tenet of the study of domain specificity as I will define it here.

The rest is in the details. Those details, however, are so critically important in any given case that they make the central tenet almost useless by itself. It is true that mechanisms entail domains. However, nothing follows specifically from this fact about how many adaptations the mind must contain “how specialized” they must be. The answers to those questions depend on particular details of evolutionary history. However, when knowledge of that history is combined with principles of cognitive engineering, the central principle of domain specificity is a powerful tool for the empirical exploration of mind design. The rest of the chapter will be devoted to explaining this principle, showing how it manifests in actual cognitive architecture, and exploring how it can be used as a tool for research.