Behavioral phenotypes: conceptual and methodological issues.

Specific behavioral patterns associated with chromosomal and genetic disorders are being recognized more frequently. The hope is that the demonstration of a behavioral phenotype with a particular syndrome may lead to the isolation of the behavior's genetic determinants. Three issues are considered here: the problem of defining a behavioral phenotype, the difficulty of demonstrating the existence of a behavioral phenotype, and the likelihood of characterizing etiologically important genes. Although there are many impediments to success, the value of recognizing behavioral phenotypes within a diagnostic syndrome is emphasized, and examples are given of how this may lead to isolating behavioral genes.