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]
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]
Evolutionary psychology is a theoretical approach in psychology that examines cognition and behavior from a modern evolutionary perspective. It seeks to identify human psychological adaptations with regards to the ancestral problems they evolved to solve. In this framework, psychological traits and mechanisms are either functional products of natural and sexual selection or non-adaptive by-products of other adaptive traits.
Incest is human sexual activity between family members or close relatives. This typically includes sexual activity between people in consanguinity, and sometimes those related by affinity, adoption, or lineage. It is strictly forbidden and considered immoral in most societies, and can lead to an increased risk of genetic disorders in children.
An incest taboo is any cultural rule or norm that prohibits sexual relations between certain members of the same family, mainly between individuals related by blood. All human cultures have norms that exclude certain close relatives from those considered suitable or permissible sexual or marriage partners, making such relationships taboo. However, different norms exist among cultures as to which blood relations are permissible as sexual partners and which are not. Sexual relations between related persons which are subject to the taboo are called incestuous relationships.
Edvard Alexander Westermarck was a Finnish philosopher and sociologist. Among other subjects, he studied exogamy and the incest taboo.
A kibbutz is an intentional community in Israel that was traditionally based on agriculture. The first kibbutz, established in 1910, was Degania. 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. In recent decades, some kibbutzim have been privatized and changes have been made in the communal lifestyle. A member of a kibbutz is called a kibbutznik.
In psychology and ethology, imprinting is any kind of phase-sensitive learning that is rapid and apparently independent of the consequences of behaviour. It was first used to describe situations in which an animal or person learns the characteristics of some stimulus, which is therefore said to be "imprinted" onto the subject. Imprinting is hypothesized to have a critical period.
Exogamy is the social norm of mating or marrying outside one's social group. The group defines the scope and extent of exogamy, and the rules and enforcement mechanisms that ensure its continuity. One form of exogamy is dual exogamy, in which two groups continually intermarry with each other.
Consanguinity is the characteristic of having a kinship with a relative who is descended from a common ancestor.
Genetic sexual attraction is a theory that attraction may be a product of genetic similarities. There is "little scientific evidence" for the position, and at least some commentators regard the hypothesis as pseudoscience. The term is also used for a supposed phenomenon in which biologically related persons separated at a young age develop intense feelings—including sexual attraction—upon the restoration of contact.
Tongyangxi, also known as Shim-pua marriage in Min Nan, was a tradition of arranged marriage dating back to pre-modern China, in which a family would adopt a pre-adolescent daughter as a future bride for one of their pre-adolescent sons, and the children would be raised together.
A psychological adaptation is a functional, cognitive or behavioral trait that benefits an organism in its environment. Psychological adaptations fall under the scope of evolved psychological mechanisms (EPMs), however, EPMs refer to a less restricted set. Psychological adaptations include only the functional traits that increase the fitness of an organism, while EPMs refer to any psychological mechanism that developed through the processes of evolution. These additional EPMs are the by-product traits of a species’ evolutionary development, as well as the vestigial traits that no longer benefit the species’ fitness. It can be difficult to tell whether a trait is vestigial or not, so some literature is more lenient and refers to vestigial traits as adaptations, even though they may no longer have adaptive functionality. For example, xenophobic attitudes and behaviors, some have claimed, appear to have certain EPM influences relating to disease aversion, however, in many environments these behaviors will have a detrimental effect on a person's fitness. The principles of psychological adaptation rely on Darwin's theory of evolution and are important to the fields of evolutionary psychology, biology, and cognitive science.
Incest between twins or "twincest" is a subclass of sibling incest and includes both heterosexual and homosexual relationships.
Alliance theory, also known as the general theory of exchanges, is a structuralist method of studying kinship relations. It finds its origins in Claude Lévi-Strauss's Elementary Structures of Kinship (1949) and is in opposition to the functionalist theory of Radcliffe-Brown. Alliance theory has oriented most anthropological French works until the 1980s; its influences were felt in various fields, including psychoanalysis, philosophy and political philosophy.
Kin recognition, also called kin detection, is an organism's ability to distinguish between close genetic kin and non-kin. In evolutionary biology and psychology, such an ability is presumed to have evolved for inbreeding avoidance, though animals do not typically avoid inbreeding.
Laws regarding incest vary considerably between jurisdictions, and depend on the type of sexual activity and the nature of the family relationship of the parties involved, as well as the age and sex of the parties. Besides legal prohibitions, at least some forms of incest are also socially taboo or frowned upon in most cultures around the world.
Siblings play a unique role in one another's lives that simulates the companionship of parents as well as the influence and assistance of friends. Because siblings often grow up in the same household, they have a large amount of exposure to one another, like other members of the immediate family. However, though a sibling relationship can have both hierarchical and reciprocal elements, this relationship tends to be more egalitarian and symmetrical than with family members of other generations. Furthermore, sibling relationships often reflect the overall condition of cohesiveness within a family.
The History of Human Marriage is an 1891 book by the Finnish philosopher and anthropologist Edvard Westermarck that provides an overview of marriage over time.
Inbreeding avoidance, or the inbreeding avoidance hypothesis, is a concept in evolutionary biology that refers to the prevention of the deleterious effects of inbreeding. Animals only rarely exhibit inbreeding avoidance. The inbreeding avoidance hypothesis posits that certain mechanisms develop within a species, or within a given population of a species, as a result of assortative mating and natural and sexual selection, in order to prevent breeding among related individuals. Although inbreeding may impose certain evolutionary costs, inbreeding avoidance, which limits the number of potential mates for a given individual, can inflict opportunity costs. Therefore, a balance exists between inbreeding and inbreeding avoidance. This balance determines whether inbreeding mechanisms develop and the specific nature of such mechanisms.
In the United States, the legality of incest varies widely between jurisdictions regarding both the definition of the offense and penalties for its commission.
Eran Shor is an Israeli-Canadian sociologist and a Professor of Sociology. He is the William Dawson Scholar at McGill University. His research interests include the causes and effects of political conflict and violence, ethnicity and nationalism, the sociology of health, and the media coverage of women and ethnic minorities. He focuses on the relationship between states’ counterterrorist policies and their respect for human rights and civil liberties. His research methods include computational analysis of big data, cross-national regression analysis and meta-analyses, as well as in-depth qualitative methods and content analysis.
