The child-rearing practices of the kibbutz system are sometimes cited as an example of the Westermarck effect. Seen here are a group of children in Kibbutz Gan Shmuel, circa 1935–40.

The Westermarck effect, also known as reverse sexual imprinting, is a psychological hypothesis that states that people tend not to be attracted to peers with whom they lived like siblings before the age of six. This hypothesis was first proposed by Finnish anthropologist Edvard Westermarck in his book The History of Human Marriage (1891) as one explanation for the incest taboo.[1]

Research since Westermarck

The Westermarck effect has gained some empirical support.[2] Proponents point to evidence from the Israeli kibbutz system, from the Chinese Shim-pua marriage customs, and from closely related families.

In the case of the Israeli kibbutzim (collective farms), children were reared somewhat communally in peer groups, based on age, not biological relations. 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 14 were between children from the same peer group. Of those 14, none had been reared together during the first six years of life. This result suggests that the Westermarck effect operates from birth to at least the age of six.[3]

In Shim-pua marriages, a girl would be adopted into a family as the future wife of a son, often an infant at that time. These marriages often failed, as would be expected according to the Westermarck hypothesis.[4]

Studies show that cousin-marriage in Lebanon has a lower success rate if the cousins were raised in sibling-like conditions, first-cousin unions being more successful in Pakistan if there was a substantial age difference, as well as reduced marital appeal for cousins who grew up sleeping in the same room in Morocco. Evidence also indicates that siblings separated for extended periods of time since childhood were more likely to report having engaged in sexual activity with one another.[5]


Eran Shor and Dalit Simchai revisited the kibbutzim results and found sexual attraction where it had not been acted on. They conclude that any innate aversion needs to be backed up by social pressures and norms.[6]

See also


  1. ^ Hou, Bowen; Wang, Yan (2021-04-21). "Westermarck Effect and Imprinting". Encyclopedia of Evolutionary Psychological Science. pp. 8496–8498. doi:10.1007/978-3-319-19650-3_3618. ISBN 978-3-319-19650-3. S2CID 241044443. Retrieved 2022-11-13.
  2. ^ Inbreeding, Incest, and the Incest Taboo: The State of Knowledge at the Turn of the Century, Arthur P. Wolf and William H. Durham (Editors), Stanford University Press, 2004, ISBN 978-0804751414. Introduction
  3. ^ Shepher, Joseph (1983). Incest: A Biosocial View. Studies in anthropology. New York: Academic Press. ISBN 0-12-639460-1. LCCN 81006552.
  4. ^ Wilson, Margo; Daly, Martin (1992). "Chapter 7: The Man Who Mistook His Wife for a Chattel". In Barkow, J.H.; Cosmides, L.; Tooby, J. (eds.). The Adapted Mind. Evolutionary psychology and the generation of culture. New York: Oxford University Press. ISBN 978-0-19-510107-2. p. 190
  5. ^ Scheidel, Walter. "Evolutionary psychology and the historian." The American Historical Review 119, no. 5 (2014): 1563-1575.
  6. ^ Shor, Eran; Simchai, Dalit (2009). "Incest Avoidance, the Incest Taboo, and Social Cohesion: Revisiting Westermarck and the Case of the Israeli Kibbutzim". American Journal of Sociology. 114 (6): 1803–1842. doi:10.1086/597178. PMID 19852254. S2CID 27854996.

Further reading