First published in 1987. Contemporary psychology is increasingly diversified, pluralistic, and specialized, and most psychologists venture beyond the confines of their substantive specialty only rarely. Yet psychologists with different specialties encounter similar problems, ask similar questions, and share similar concerns. Unfortunately, there are very few arenas available for the expression or exploration of what is common across psychological subdisciplines. The Crosscurrents in Contemporary Psychology series is intended to serve as such a forum. The chief aim of this series is to provide integrated perspectives on supradisciplinary themes in psychology. Despite its contemporary diversity and high degree of specialization, psychology embraces many phenomena that are of interest across subdisciplines largely because of the generality and ubiquity of those phenomena. The sensitive period is one. Sensitivity to different kinds of experience varies over the life cycle of an organism.