Imprinting is the term used in psychology and ethology to describe any kind of phase-sensitive learning (learning occurring at a particular age or a particular life stage) that is rapid and apparently independent of the consequences of behavior. It was first used to describe situations in which an animal or person learns the characteristics of some stimulus, which is therefore said to be "imprinted" onto the subject.
Imprinting is hypothesized to have a critical period.
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The best-known form of imprinting is filial imprinting, in which a young animal acquires several of its behavioral characteristics from its parent. It is most obvious in nidifugous birds, which imprint on their parents and then follow them around. It was first reported in domestic chickens, by the 19th-century amateur biologist Douglas Spalding. It was rediscovered by the early ethologist Oskar Heinroth, and studied extensively and popularized by his disciple Konrad Lorenz working with greylag geese. Lorenz demonstrated how incubator-hatched geese would imprint on the first suitable moving stimulus they saw within what he called a "critical period" between 13–16 hours shortly after hatching. For example, the goslings would imprint on Lorenz himself (to be more specific, on his wading boots), and he is often depicted being followed by a gaggle of geese who had imprinted on him. Filial imprinting is not restricted to non-human animals that are able to follow their parents, however. In child development, the term is used to refer to the process by which a baby learns who its mother and father are. The process is recognised as beginning in the womb, when the unborn baby starts to recognise its parents' voices.[1]
The filial imprinting of birds was a primary technique used to create the movie Winged Migration (Le Peuple Migrateur), which contains a great deal of footage of migratory birds in flight. The birds imprinted on handlers, who wore yellow jackets and honked horns constantly. The birds were then trained to fly along with a variety of aircraft, primarily ultralights.
The Italian hang-glider pilot Angelo d'Arrigo extended this technique. D'Arrigo noted that the flight of a non-motorised hang-glider is very similar to the flight patterns of migratory birds: Both use updrafts of hot air (thermal currents) to gain altitude that then permits soaring flight over distance. He used this fact to enable the re-introduction into the wild of threatened species of raptors.
Birds that are hatched in captivity have no mentor birds to teach them their traditional migratory routes. D'Arrigo had one solution to this problem. The chicks hatched under the wing of his glider, and imprinted on him. Then, he taught the fledglings to fly and to hunt. The young birds followed him not only on the ground (as with Lorenz) but also in the air as he took the path of various migratory routes. He flew across the Sahara and over the Mediterranean Sea to Sicily with eagles, from Siberia to Iran (5,500 km) with a flock of Siberian cranes, and over Mount Everest with Nepalese eagles. In 2006, he worked with a condor in South America.
In a similar project, orphaned Canada Geese were trained to their normal migration route by the Canadian ultralight enthusiast Bill Lishman, as shown in the fact-based movie drama Fly Away Home.
Chicks of domestic chickens prefer to be near large groups of objects that they have imprinted on. This behaviour was used to determine that very young chicks of a few days old have rudimentary counting skills. In a series of experiments, they were made to imprint on plastic balls and could figure out which of two groups of balls hidden behind screens had the most balls.[2]
Sexual imprinting is the process by which a young animal learns the characteristics of a desirable mate. For example, male zebra finches appear to prefer mates with the appearance of the female bird that rears them, rather than mates of their own type.[3]
Sexual imprinting on inanimate objects is a popular theory concerning the development of sexual fetishism. For example, according to this theory, imprinting on shoes or boots (as with Konrad Lorenz' geese) would be the cause of shoe fetishism.
Reverse sexual imprinting is also seen in instances where two people who live in close domestic proximity during the first few years in the life of either one become desensitized to later close sexual attraction. This phenomenon, known as the Westermarck effect, was first formally described by Finnish anthropologist Edvard Westermarck in his book The History of Human Marriage (1891). The Westermarck effect has since been observed in many places and cultures, including in the Israeli kibbutz system, and the Chinese Shim-pua marriage customs, as well as in biological-related families.
In the case of the Israeli kibbutzim (collective farms), children were reared somewhat communally in peer groups, based on age, not biological relation. A study of the marriage patterns of these children later in life revealed that out of the nearly 3,000 marriages that occurred across the kibbutz system, only fourteen were between children from the same peer group. Of those fourteen, none had been reared together during the first six years of life. This result provides evidence not only that the Westermarck effect is demonstrable but that it operates during the period from birth to the age of six.[4]
When proximity during this critical period does not occur—for example, where a brother and sister are brought up separately, never meeting one another—they may find one another highly sexually attractive when they meet as adults. This phenomenon is known as genetic sexual attraction. This observation supports the hypothesis that the Westermarck effect evolved because it suppressed inbreeding. This attraction may also be seen with cousin couples.
Freud argued that as children, members of the same family naturally lust for one another, making it necessary for societies to create incest taboos,[5] but Westermarck argued the reverse, that the taboos themselves arise naturally as products of innate attitudes.
Steven Pinker wrote on the subject:
The idea that boys want to sleep with their mothers strikes most men as the silliest thing they have ever heard. Obviously, it did not seem so to Freud, who wrote that as a boy he once had an erotic reaction to watching his mother dressing. But Freud had a wet-nurse, and may not have experienced the early intimacy that would have tipped off his perceptual system that Mrs. Freud was his mother. The Westermarck theory has out-Freuded Freud.—Steven Pinker, How the Mind Works
Researchers have noted that computer users exhibit preferences towards the first system they learn, then judge other systems by their similarity to that first system. The result is that "users generally prefer systems similar to those they learned on and dislike unfamiliar systems."[6]
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