Westermarck effect

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 cousins 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.

[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.

[5] Eran Shor and Dalit Simchai revisited the kibbutzim results and found sexual attraction where it had not been acted on.

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.