The Effects of Rearing Experiences: The Early Years

Abstract

Perhaps the most basic tenet of development is that behavior is subject to the multiple influences of genes and environments. In fact, it is the dynamic, temporal interaction between genetic and environmental factors that yields different developmental outcomes. Few would disagree with this view today. However, in the middle of the 20th century, when experimental rearing paradigms were first developed and studied in rhesus macaques, the view was different. Behavior patterns were construed as being controlled by either genes or the environment. Ethologists studied species-typical behaviors called fixed action patterns— “fixed” because they were thought to be uninfluenced by experience. In a similar manner, psychologists studied learned behavior that was thought not to have any genetic basis. This dichotomous view permeated the science of the time. Some took on the task of “proving” that specific behavior patterns were innate and developing the methodology to do so (Lorenz, 1950); others attempted to show that organisms were essentially molded by their experiences (Skinner, 1975). There were other voices arguing that all behavior was under both genetic and environmental control (Lehrman, 1970; Schneirla, 1957), but this interactionist notion had not yet taken firm hold. It is important to remember that the early studies of rearing in nonhuman primates took place in this context.