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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 typically involves an animal or person learning the characteristics of some stimulus, which is therefore said to be "imprinted" onto the subject.
The best known form of imprinting is filial imprinting, in which a young animal learns the characteristics of its parent. It is most obvious in nidifugous birds, who 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 popularised 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" of about 36 hours shortly after hatching. Most famously, the goslings would imprint on Lorenz himself (more specifically, 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 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.
The filial imprinting of birds was a primary technique used to create the movie 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 has 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 which then permits soaring flight over distance. He used this fact to enable the re-introduction into the wild of threatened species of raptors.
Birds which are hatched in captivity have no mentor birds to teach them their traditional migratory routes. D'Arrigo has one solution to this problem. The chicks hatch under the wing of his glider, and imprint on him. Subsequently, he teaches the fledglings to fly and to hunt. The young birds follow him not only on the ground (as with Lorenz) but also in the air. He then shows them the routes to fly. He has flown 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 Everest with Nepalese eagles. In March 2005, he began imprinting a newly hatched condor.
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.
Sexual imprinting on objects other than people is the most popular theory of the development of sexual fetishism. For example, according to this theory, imprinting on shoes or boots (as with Lorenz' geese) would be the cause of shoe fetishism.
Reverse sexual imprinting is also seen: when two people live in close domestic proximity during the first few years in the life of either one, both are desensitized to later close sexual attraction and bonding. This phenomenon, known as the Westermarck effect, was discovered by anthropologist Edvard Westermarck. The Westermarck effect has since been observed in many places and cultures, including in the Israeli kibbutz system, and the Shim-pua marriage customs of Taiwan, as well as in biological-related families.
In the case of the Israeli kibbutz farms, these children grew up in a common children's house, away from their parents. They spent the entire day and night together. This did result in a generation that was not interested in the opposite sex within their class, and the program was dropped. It is an extreme example of grouping since the adults were also removed from the environment.
When this does not occur, for example where a brother and sister are brought up not knowing about one another, they may find one another highly sexually attractive when they meet as adults: a phenomenon known as genetic sexual attraction. This observation is consistent with the theory that the Westermarck effect evolved to suppress inbreeding.
Westermarck vs. Freud
Freud argued that members of the same family naturally lust for one another, making it necessary for societies to create incest taboos, but Westermarck argued the reverse, that the taboos themselves arise naturally as products of a simple inherited epigenetic response. Subsequent research over the years supports Westermarck's observations and interpretation. But still psychoanalysts do agree with and support Freudian concept. One argument used to support their stance is that such taboos would obviously be meaningless if there was no desire to perform the acts in question.
- Sluckin, W_ (1964) Imprinting and Early Learning, London: Methuen.
- Westermarck, E. A. The history of human marriage, 5th edn. London: Macmillan, 1921.
- Bateson, P.P. (1966) The characteristics of content of imprinting, Biological Review 41: 177-211.
- Canon, P. (1959) Socialisation and imprinting in brown leghorn chicks, Animal Behaviour 7: 26-34.
- Hess, E.H. (1958) 'Imprinting' in animals, Scientific American 198(3): 81-90.
- Hess, E.H. (1972) 'Imprinting' in a natural laboratory, Scientific American 227(2): 24-31.
- Moltz, H. (1960) Imprinting: empirical basis and theoretical significance, Psychological Bulletin 57: 291-314
- Ramsey, A.O. and Hess, E. (1954) A laboratory approach to the study of imprinting, Wilson Bulletin 66:196-206.
- Sluckin, W. and Salzen, E.A. (1961) Imprinting and perceptual learning, Quarterly Journal of Experimental Psychology 13: 65-77.
- Cardoso, SH and Sabbatini, RME. Learning who is your mother. The behavior of imprinting. Brain & Mind Magazine.
- Nancy T. Burley, a researcher into imprinting in zebra finches
- Debra Lieberman, John Tooby and Leda Cosmides. "Does morality have a biological basis? An empirical test of the factors governing moral sentiments relating to incest." Accepted for publication in Proc. R. Soc. Lond. B November 2002. Available online at Citeseer
- Angelo d'Arrigo personal website
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