F1, an Austrian zoologist, was among the first to describe attachment behaviors of geese soon after hatching. In his classic experiment, Lorenz divided eggs laid by a greylag gooseinto two groups. One of the groups was hatched by their mother and immediately began following her around. The second group was hatched in an incubator, but in the absence of their mother, they began instead to follow Lorenz. Even if Lorenz placed the goslings in a box so that both groups were separated from their mother or himself, they would reliably segregate toward their mother or toward Lorenz, according to whom they were first exposed. Although he was the first to name this phenomenon "imprinting," earlier scientists had made similar observations. Later investigators would determine that imprinting in ducks, geese, and other species of birds occurs between 12 and 17 hours after hatching, which led to the notion that there are "critical periods" in the development of the brain and behavior (1). Overall, Konrad Lorenz’s experiments pointed the way toward our understanding that early experience helps to shape social behavior in adulthood.