Behavioral imprinting is observed in some newborn animals and occurs when they develop strong and specific attachments to another animal (usually a parent) following brief, early-life exposures. Offspring imprint onto parents within a brief period after birth or hatching; this time window is called the critical period. Once imprinting occurs, the bond established between the parents and their offspring is usually long-lasting.
Mother sheep imprint onto the scent of their lambs within a few hours after their birth. Since many females in the herd give birth at the same time of year, imprinting allows the mothers to selectively recognize and care for their lambs.
Imprinting also occurs in the opposite direction, with offspring imprinting onto their parents. This is particularly common in waterfowl, such as goslings (baby geese), which imprint onto their mother on the first day after hatching. Afterward, they follow the mother wherever she goes. This behavior allows the mother to protect her offspring and teach them the skills they need to survive.
In the 1930s, Konrad Lorenz showed that goslings imprint onto the first large, moving object they see during the critical period. In the absence of their mother, this object could be siblings, a person, or even an inanimate object. After that, they will always follow this substitute “mother,” called the imprinting stimulus, even when presented with their biological mother or other adult geese.
These experiments showed that the stimuli present in the environment determine the object of imprinting during the critical period. Therefore, imprinting results from a combination of the instinctive behavior to imprint and learning based on experience.
Imprinting occurs only within the critical period and cannot be changed after the critical period ends. This is why goslings that have imprinted onto a human will continue to follow the human later in life, even when exposed to their mother. If there is no appropriate imprinting stimulus during the critical period, the young animals will never imprint at all.