Idealisation meets psychometrics: The case for the right groups and the right individuals

Abstract

We consider some of the methodological issues involved in using data from brain-damaged individuals in support (or disproof) of claims about the structure of normal cognition. More specifically, we address whether single cases or group studies provide a more reliable and valid source of relevant information. We conclude that the dichotomy is itself misconceived if approached from a purely methodological stance, and that selection of a particular group (or individual) must be based upon the precise nature of the theoretical claims under consideration. The status of “minority effects” in group studies is determined, we argue, by whether they arise from biological variation in fixed functional architecture or from “strategic” variation within a common architecture.