First Published in 1995. Behavioral Development is Volume 1 in the Research and Developmental and Comparative Psychology series - dedicated to honour the contributions of T. C. Schneirla. This volume represents the substantive content of the Fifth T. C. Schneirla Conference, held in November of 1989. The volume is divided into three parts: the significance of the intensity of the adequate stimulus; the process of development and the concept of integrative levels. Schneirla is still recognized as one of the foremost theoreticians in comparative psychology, and the rebirth of interest in comparative psychology is evident.