From Freud to a modern understanding of behavioral, physiological, and brain development.

Seymour Levine's first "early experience" experiments were inspired by Freud. Yet, Levine's lifetime of work, and the work of his colleagues and scientists who followed, unveiled a myriad of early experience effects that even Freud himself could not have imagined. Related to and extending beyond his work on early experience, Levine also made important, often seminal, contributions to overlapping and related areas, such as early maternal separation and deprivation, maternal behavior and physiology, sexual differentiation, perinatal malnutrition, attachment in non-human primates, hypothalamic-pituitary-adrenal (HPA) stress reactivity and its adaptive significance, and the development of the HPA system. Moreover, his work spawned new lines of research by investigators active today. The papers contained in this special issue provide a sampling of research demonstrating some of the important directions in which those earliest experiments have led, many with clinical applications.