Editing Incest taboo (section)

====Westermarck effect====
{{main|Westermarck effect}}
The [[Westermarck effect]], first proposed by [[Edvard Westermarck]] in 1891, is the theory that children reared together, regardless of biological relationship, form a sentimental attachment that is by its nature non-erotic.<ref>Westermarck, Edvard A. (1921). ''The history of human marriage'', 5th edn. London: Macmillan</ref> [[Melford Spiro]] argued that his observations that unrelated children reared together on Israeli Kibbutzim nevertheless avoided one another as sexual partners confirmed the Westermarck effect.<ref>Spiro, M. (1965). Children of the Kibbutz. New York: Schocken.</ref> Joseph Shepher in a study examined the second generation in a [[kibbutz]] and found no marriages and no sexual activity between the adolescents in the same peer group. This was not enforced but voluntary. Looking at the second generation adults in all kibbutzim, out of a total of 2769 marriages, none were between those of the same peer group.<ref>{{Cite journal | last1 = Shepher | first1 = J. | title = Mate selection among second generation kibbutz adolescents and adults: Incest avoidance and negative imprinting | doi = 10.1007/BF01638058 | journal = Archives of Sexual Behavior | volume = 1 | issue = 4 | pages = 293–307 | year = 1971 | pmid =  24179077| s2cid = 25602623 }}</ref>

However, according to a book review by John Hartung of a book by Shepher, out of 2516 marriages documented in Israel, 200 were between couples reared in the same kibbutz. These marriages occurred after young adults reared on kibbutzim had served in the military and encountered tens of thousands of other potential mates, and 200 marriages is higher than what would be expected by chance. Of these 200 marriages, five were between men and women who had been reared together for the first six years of their lives.<ref>{{cite journal | last1 = Hartung | first1 = John | year = 1985 | title = Review of ''Incest: A Biological View'' by J. Shepher | doi = 10.1002/ajpa.1330670213 | journal = American Journal of Physical Anthropology | volume = 67 | pages = 167–171 }}</ref>

A study in Taiwan of marriages where the future bride is adopted in the groom's family as an infant or small child found that these marriages have higher infidelity and divorce and lower fertility than ordinary marriages; it has been argued that this observation is consistent with the Westermarck effect.<ref>Wolf, A. 1995. ''Sexual attraction and childhood association: a Chinese brief for Edward Westermarck''. Stanford, CA: Stanford University Press.</ref>