Methods of Studying Small Samples: Issues and Examples
Elizabeth Bates University of California, San Diego
Mark Appelbaum Vanderbilt University
Developmental cognitive neuroscience is devoted to the study of brain- behavior relationships, and the way that those relationships develop over time. One of the most important methodologies within this growing field is the study of rare clinical populations that present unusual profiles of language, cognition and/or social-emotional development. For example, older children and adolescents with Williams syndrome display remarkable sparing of language and social interaction, despite severe deficits in many other aspects of cognition and perception ( Bellugi, Bihrle, Trauner, Jernigan, & Doherty, 1990; Bellugi, Marks, Bihrle, & Sabo, 1988). Many autistic children display what appears to be a contrasting and perhaps complementary pattern: particularly severe deficits in language and avoidance of social interaction, despite islands of normal or (in some cases) supranormal ability in some domains of spatial cognition ( Rutter, 1978). If these complementaries at the behavioral level could be mapped onto contrasting and complementary patterns of brain morphology, we could learn a great deal about the brain systems responsible for the behaviors in question. Indeed, recent neuroanatomical studies of Williams syndrome ( Jernigan & Bellugi, 1990; Jernigan, Bellugi, & Hesselink, 1989) and autism ( Courchesne, 1991) do provide evidence for contrasting forms of brain organization, including contrasts in areas that were traditionally excluded from consideration in speculations about the brain bases of higher-order cognitive functions (e.g., the cerebellum).
These are dramatic findings, the kind of result that could inspire whole new