ABSTRACT
The theory of sensitive periods during behavioral development postulates that age-based periods are optimal or most vulnerable to environmental stimulation. This theory has guided much research but has come under fire recently from a variety of directions, especially regarding human development. This chapter reviews the data and theory relevant to the proper status of the concept in the views of human and animal social development. It examines the roles of early experience and relative plasticity in the development of social behavior in animals and humans. The concept of a sensitive period hypothesizes age-based periods during which the organism is most vulnerable to environmental stimulation. In 1979, Bateson points out that a large variety of terms have been used to describe basically the same phenomenon and that no term has received general adoption. In 1976, H. F. Harlow successfully rehabilitated separation-induced depressive disorders in rhesus monkeys by providing them with opportunities to interact with same-age monkeys.
