The Westermarck effect, or reverse sexual imprinting, is a hypothetical psychological effect through which people who live in close domestic proximity during the first few years of their lives become desensitized to later sexual attraction

Sexual attraction

Sexual attractiveness or sex appeal refers to an individual's ability to attract the sexual or erotic interest of another person, and is a factor in sexual selection or mate choice. The attraction can be to the physical or other qualities or traits of a person, or to such qualities in the context...

. This phenomenon was first hypothesized by Finnish anthropologist Edvard Westermarck

Edvard Westermarck

Edvard Alexander Westermarck was a Swedish-speaking Finnish philosopher and sociologist. Among other subjects, he studied exogamy and the incest taboo....

 in his book The History of Human Marriage (1891). Observations interpreted as evidence for the Westermarck effect have since been made in many places and cultures, including in the Israel

Israel

The State of Israel is a parliamentary republic located in the Middle East, along the eastern shore of the Mediterranean Sea...

i kibbutz

Kibbutz

A kibbutz is a collective community in Israel that was traditionally based on agriculture. Today, farming has been partly supplanted by other economic branches, including industrial plants and high-tech enterprises. Kibbutzim began as utopian communities, a combination of socialism and Zionism...

 system, and the Chinese Shim-pua marriage

Shim-pua marriage

Tongyangxi , also known as Shim-pua marriage in Taiwanese , was a tradition of arranged marriage dating back to pre-modern China, in which a poor family would sell a child, a pre-adolescent daughter to a richer family as a servant or a caretaker. In exchange, the girl would be married into the...

 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 suggests that the Westermarck effect operates during the period from birth to the age of six.

When proximity during this critical period

Critical period

This article is about a critical period in an organism's or person's development. See also America's Critical Period.In general, a critical period is a limited time in which an event can occur, usually to result in some kind of transformation...

 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, according to the hypothesis of genetic sexual attraction

Genetic sexual attraction

Genetic sexual attraction is a term that describes the phenomenon of sexual attraction between close relatives, such as siblings, first and second cousins or a parent and offspring, who first meet as adults.- History and definition :...

 (q.v.). This supports the claim that the Westermarck effect evolved because it suppressed inbreeding

Inbreeding

Inbreeding is the reproduction from the mating of two genetically related parents. Inbreeding results in increased homozygosity, which can increase the chances of offspring being affected by recessive or deleterious traits. This generally leads to a decreased fitness of a population, which is...

.

Westermarck and Freud

Freud

Sigmund Freud

Sigmund Freud , born Sigismund Schlomo Freud , was an Austrian neurologist who founded the discipline of psychoanalysis...

 argued that as children, members of the same family

Family

In human context, a family is a group of people affiliated by consanguinity, affinity, or co-residence. In most societies it is the principal institution for the socialization of children...

 naturally lust for one another, making it necessary for societies

Society

A society, or a human society, is a group of people related to each other through persistent relations, or a large social grouping sharing the same geographical or virtual territory, subject to the same political authority and dominant cultural expectations...

 to create incest taboo

Incest taboo

An Incest taboo is any cultural rule or norm that prohibits practices of sexual relations between relatives. All human cultures have norms regarding who is considered suitable and unsuitable sexual and/or marriage partners, and usually certain close relatives are excluded as possible partners...

s, but Westermarck argued the reverse, that the taboos themselves arise naturally as products of innate attitudes.

Steven Pinker

Steven Pinker

Steven Arthur Pinker is a Canadian-American experimental psychologist, cognitive scientist, linguist and popular science author...

 wrote on the subject:

Notations

• Paul, Robert A. (1988). Psychoanalysis and the Propinquity Theory of Incest Avoidance. The Journal of Psychohistory 3 (Vol. 15), 255–261.
• Spain, David H. (1987). The Westermarck–Freud Incest-Theory Debate: An Evaluation and Reformation. Current Anthropology 5 (Vol. 28), 623–635, 643–645.
• Westermarck, Edvard A. (1921). The history of human marriage, 5th edn. London: Macmillan.