The Westermarck effect: the lack of desire towards childhood friends

March 29, 2024

There are many people who are interested in knowing what characteristics and styles of behavior enhance personal appeal, but fewer are also trying to know things about the factors that kill any possibility of attraction.

That is why it is not strange that so little is known about Westermarck effect , a hypothetical psychological phenomenon according to which human beings are predisposed to not feel sexual desire towards people with whom we relate continuously during our early childhood, regardless of whether they are relatives or not.

Why could this curious trend occur? The proposals of explanation that many researchers shuffle to solve the question of the Westermarck effect have to do with the phenomenon of incest .

Incest, universal taboo

In all current societies there are taboos, that is to say, behaviors and ideas that are not accepted socially for reasons that have to do, at least in part, with the dominant moral or the religious beliefs associated with that culture. To some of these taboos, such as intentional homicide or cannibalism, it is easy to find them inconvenient from a pragmatic point of view, because if they become generalized, they could destabilize the social order and produce an escalation of violence, among other things.

However, there is a universal taboo that we can find in practically all cultures throughout history but whose prohibition is difficult to justify rationally: the incest.

Keeping this in mind, Many researchers have asked what is the origin of the omnipresent rejection that generates everything related to family relationships . Among all the hypotheses, there is one that has gained strength in recent decades and is based on a psychological effect based on the combination between genetic innateness and learned behaviors. This is the hypothesis of the Westermarck effect.

Matter of probabilities

Edvard Alexander Westermarck was a Finnish anthropologist born in the mid-nineteenth century known for his theories about marriage, exogamy and incest. Regarding the latter, Westermarck proposed the idea that the avoidance of incest is the product of natural selection . For him, avoiding reproduction among relatives would be part of an adaptive mechanism that we carry in the genes and that would have spread among the population due to the advantage of this behavior in evolutionary terms.

As the offspring born of incest can have serious health problems, the selection would have carved in our genetics a mechanism for us to feel aversion for it, which would be in itself an adaptive advantage.

Ultimately, Westermarck believed that natural selection has shaped the sexual tendencies of our entire species by preventing relationships between close relatives.

Suppressing sexual attraction to avoid incest

But, how would natural selection do to promote incest avoidance behaviors? After all, there is no trait by which we can recognize brothers and sisters with the naked eye. According to Westermarck, evolution has decided to pull statistics to create a mechanism of aversion between family members. As people who during the first years of life are seen daily and belong to the same environment have many possibilities of being related, the criterion that serves to suppress sexual attraction is the existence or not of proximity during childhood.

This predisposition to not feel attracted by the people with whom we come in contact periodically during the first moments of our life would be of genetic bases and would suppose an evolutionary advantage; but, as a result of this, we would not have sexual interest in old childhood friendships either .

The anti - Oedipus

To better understand the mechanism through which the Westermarck effect is articulated, it is useful to compare this hypothesis with the ideas about incest proposed by Sigmund Freud.

Freud identified the taboo of incest as a social mechanism to repress sexual desire towards close relatives and thus make possible the "normal" functioning of society. The Oedipus complex would be, according to him, the way in which the subconscious fits this blow directed against the sexual inclinations of the individual , from which it follows that the only thing that makes the practice of incest is something generalized is the existence of taboo and the punishments associated with it.

The biologist's conception of the Westermarck effect, however, Attends directly against what is proposed in the Oedipus complex , since in its explanation of the facts the taboo is not the cause of the sexual rejection, but the consequence.This is what makes some evolutionary psychologists hold the idea that it is evolution, rather than culture, that speaks through our mouths when we express our opinion about incest.

Some studies on the Westermarck effect

The proposal of the Westermarck effect is very old and has been buried by a flood of criticisms coming from anthropologists and psychologists who defend the important role of learned behaviors and cultural dynamics in sexuality. However, little by little it has been raising its head until accumulating enough evidence in its favor.

When we talk about the evidence that reinforces the Westermarck hypothesis, the first case that is named is usually that of J. Sheper and his study on resident populations in kibbutz (communes based on the socialist tradition) of Israel, in which many unrelated children are raised together. Even though the contacts between these children are constant and lengthen until they reach adulthood, Sheper concluded that the occasions in which these people get to have sexual intercourse are rare at some point in their life, being much more likely to end up marrying others.

Other interesting examples

Since the publication of Sheper's article, criticisms have been made about the methodology used to measure sexual attraction without cultural or sociological factors interfering. However, many other studies that reinforce the Westermarck effect hypothesis have also been published.

For example, an investigation based on past questioning of the Moroccan population showed that the fact of having a close and continuous relationship with someone during early childhood (regardless of whether they are related or not) makes it much more likely that when they reach adulthood they will feel an aversion to the idea of marrying this person.

Lack of attraction present even in 'Westermarck marriages'

In addition, in cases where two people who have been raised together without sharing blood ties are married (for example, by imposition of adults), tend not to leave offspring due perhaps to the lack of attraction . This has been found in Taiwan, where there has traditionally been a custom among some families of letting the bride grow up in the house of the future husband (marriage). Shim-pua).

The taboo is linked to the continued coexistence

Evolutionary psychologist Debra Lieberman also helped reinforce the Westermarck effect hypothesis through a study in which she asked a series of people to complete a questionnaire. This file contained questions about his family, and also presented a series of censurable actions such as the use of drugs or homicide. Volunteers had to order according to the degree with which they felt bad, from more to less morally reprehensible, so that they would be placed in a sort of ranking.

In the analysis of the obtained data, Lieberman he discovered that the amount of time spent with a brother or sister during childhood correlated positively with the degree to which incest was condemned . In fact, it could be predicted to what extent a person would condemn incest just by seeing the degree of exposure to a sibling at the childhood stage. Neither the attitude of the parents nor their degree of kinship with the brother or sister (adoptions were also taken into account) affected significantly in the intensity of the rejection towards this practice.

Many doubts to be solved

We still know very little about the Westermarck effect. It is unknown, in the first place, if it is a propensity that exists in all the societies of the planet, and if it is based or not on the existence of a partially genetic trait. Of course, it is not known which genes could be involved in its functioning or , and if it manifests differently in men and women.

The answers about the psychological and universal propensities typical of our species, as always, are expected. Only decades of continuous research can bring to light these innate predispositions, buried in our body under thousands of years of adaptation to the environment.

Bibliographic references:

Bergelson, V. (2013). Vice is Nice But Incest is Best: The Problem of a Moral Taboo. Criminal Law and Philosophy, 7 (1), pp. 43 - 59.

Bittles, A. H. (1983). The intensity of human inbreeding depression. Behavioral and Brain Sciences, 6 (1), pp. 103-104.

Bratt, C. S. (1984). Incest Statutes and the Fundamental Right of Marriage: Is Oedipus Free to Marry ?. Family Law Quarterly, 18, pp. 257-309.

Lieberman, D., Tooby, J. and Cosmides, L. (2003). Does morality have a biological basis? An empirical test of the factors governing moral sentiments related to incest. Proceedings of the Royal Society of London: Biological Sciences, 270 (1517), pp. 819-826.

Shepher, J. (1971). Mate selection among second generation kibbutz adolescents and adults: incest avoidance and negative imprinting. Archives of Sexual Behavior, 1, pp. 293-307.

Spiro, M. E. (1958). Children of the Kibbutz. Cambridge: Harvard University Press. Cited in Antfolk, J., Karlsson, Bäckström, M. and Santtila, P. (2012).Disgust elicited by third-party incest: the roles of biological relatedness, co-residence, and family relationship. Evolution and Human Behavior, 33 (3), pp. 217-223.

Talmon, Y. (1964). Mate selection on collective settlements. American Sociological Review, 29 (4), pp. 491-508.

Walter, A. (1997). The evolutionary psychology of mate selection in Morocco. Human Nature, 8 (2), pp. 113 - 137.

Westermarck, E. (1891). The history of human marriage. London: Macmillan. Cited in Antfolk, J., Karlsson, Bäckström, M. and Santtila, P. (2012). Disgust elicited by third-party incest: the roles of biological relatedness, co-residence, and family relationship. Evolution and Human Behavior, 33 (3), pp. 217-223.

Wolf, A. (1970). Childhood Association and Sexual Attraction: A Further Test of the Westermarck Hypothesis. American Anthropologist, 72 (3), pp. 503-515.