ABSTRACT
Substantial information on behavioral development has been collected over the past century by comparative and developmental psychologists. Early experience can also affect behavior in subsequent stages of development. Ideally, behavioral development should be studied under natural conditions, but this is usually difficult or even impossible. A longitudinal design involves the description of developmental changes in behavior in a single group of animals observed at different ages. For example, longitudinal observations on the sensorimotor development of infant chimpanzees reared by human caretakers revealed the age of emergence of various behaviors. The order of development of the behaviors described previously is remarkably similar to that shown by human children, but there are also some differences. Altriciality is characterized by immature sensorimotor development at the time of hatching, which implies an inability to perform the kind of behavioral tasks described previously with Peking ducks, a precocial species.
