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Westermarck effect

Westermarck effect is a biology topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Westermarck effect rather than just read about it. In short: 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 1891 book, The History of Human Marriage, as one explanation for the incest taboo.

Westermarck effect — main illustration
Westermarck effect — illustration

Key takeaways

  • Westermarck effect belongs to biology; place it in that map before memorising details.
  • Learn the definition first, then one example that makes the definition concrete.
  • Connect Westermarck effect to a quantity you can measure, compute or draw — that is where exam questions come from.
  • Reproduce the core statement of Westermarck effect from memory before moving on to harder problems.

Reference excerpt

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 1891 book, The History of Human Marriage, as one explanation for the incest taboo.

Research since Westermarck The Westermarck effect has gained some empirical support. Proponents point to evidence from the Israeli kibbutz system, from 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. 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. 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. Eran Shor and Dalit Simchai revisited the kibbutzim results and found sexual attraction where it had not been acted on. They concluded that any innate aversion needs to be backed up by social pressures and norms.

See also Accidental incest Genetic sexual attraction Kibbutz communal child rearing and collective education Psychosexual development Electra complex Oedipus complex Totem and Taboo

References

Further reading Lieberman, D.; Tooby, J.; Cosmides, L. (15 February 2007). "The Architecture of Human Kin Detection". Nature. 445 (7129): 727–731. Bibcode:2007Natur.445..727L. doi:10.1038/nature05510. PMC 3581061. PMID 17301784. Paul, Robert A. (Winter 1988). "Psychoanalysis and the Propinquity Theory of Incest Avoidance". The Journal of Psychohistory. 15 (3): 255–261. Spain, David H. (December 1987). "The Westermarck–Freud Incest-Theory Debate: An Evaluation and Reformation". Current Anthropology. 28 (55): 623–635, 643–645. doi:10.1086/203603. JSTOR 2743359. S2CID 145420633. Westermarck, Edvard A. (1921). The History of Human Marriage (5th ed.). London: Macmillan. Vol. 1; Vol. 2; Vol. 3.

Illustrations

Westermarck effect: 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, c. 1935–40.
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, c. 1935–40.

Worked examples

Example 1 — a first encounter with Westermarck effect

Start with the simplest possible case. Write down what Westermarck effect claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In biology, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Westermarck effect before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Westermarck effect ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Westermarck effect

In research
Westermarck effect appears in biology research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry
Engineering practice reuses Westermarck effect in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom
Westermarck effect is common in secondary-school and first-year university syllabi. It links to neighbouring topics Child development, Evolutionary psychology, Incest, so understanding it makes those chapters shorter.
In everyday life
Look for Westermarck effect outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study Westermarck effect in 20 minutes

  1. Read the reference excerpt below once, without taking notes.
  2. Close the page and write down what Westermarck effect means in your own words.
  3. Compare your version with the excerpt and mark what you missed.
  4. Work through the three examples above with pen and paper.
  5. Explain Westermarck effect out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Westermarck effect in simple terms?

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 1…

Why does Westermarck effect matter?

Because it connects several biology ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Westermarck effect?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Westermarck effect.

Tags

  • Child development
  • Evolutionary psychology
  • Incest
  • Sexual attraction
  • Sibling

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