Within
hours after hatching, baby geese or ducks start walking about, and follow their
mother. But how do they know they are following their mother? In reality, they
don’t, and studies have shown that they follow the first suitable subject they
see within a critical period, measured in hours, and remain attached to this
individual for a lifetime. This process is called imprinting and was first
observed in about 1873 by Douglas Spaulding, an amateur English biologist, and
then rediscovered by the German biologist Oskar Heinroth. It was Heinroth’s
student, Konrad Lorenz, who was the first to study imprinting in detail, and he
was the co-recipient of the 1973 Nobel Prize for his work on this topic.
Lorenz,
an Austrian zoologist, was one of the founders of modern ethology, the study of
animal behavior. In studies conducted in about 1935, he found that after
spending their first hours with him, young greylag geese followed him rather
than their biological mother and strongly preferred him to a member of their own
species. For bird species such as geese, which are feathered and active when
hatched, the first thirteen to sixteen hours are critical periods for
imprinting to occur. In mallard ducklings and domestic chicks, the imprinting
opportunity is lost after thirty hours. By contrast, for birds that are born
naked and helpless, the critical period is extended.
A number of studies with young birds have shown that the imprinting response is innate and that the young have no inborn recognition of who is their authentic mother. |
Imprinting
is an instinctive behavioral act, which, unlike learned associative behaviors
such as classical conditioning or operant (instrumental) conditioning, occurs
without the need for reinforcement or reward. In nature, the apparent
biological function of imprinting is to recognize close relatives and establish
an intimate, mutually beneficial social bond between offspring and parent. From
the parent’s perspective, time, effort, and resources will not be expended for
the care of another’s offspring. An offspring must recognize its parent or risk
being attacked and killed by species members who are not biologically related.
Imprinting also extends to sexual preferences, so that a young animal learns
the characteristics of a suitable mate and only mates with those individuals
that are not too closely related (sibling) or too far removed (another
species).
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