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What is the Westermarck Effect?

Mary McMahon
Updated May 16, 2024
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The Westermarck effect is a phenomenon which has been observed in individuals who spend large amounts of time with each other under the age of six. People who are raised together, regardless of relationship, tend to become desensitized to each other, and they will not generally develop sexual attraction to each other later in life. A variety of studies have supported the concept of the Westermarck effect.

This idea is sometimes referred to as “reverse imprinting,” and it is named for Edvard Westermarck, a Finnish sociologist who worked and wrote in the late 1800s. He was particularly interested in marriage patterns and incest taboos, and his idea that people who are raised together will not develop sexual attraction went contradictory to the beliefs of Freud, a prominent contemporary. Over time, it has been apparent that Westermarck was vindicated, as evidence strongly suggests that Freud's ideas are not supported by actual evidence.

In addition to using data about brothers and sisters who are raised together, researchers on the Westermarck effect have also looked at situations in which non-related individuals are raised together. For example, on Israeli kibbutzim, children are often raised together in large peer groups, and members of the same peer group rarely develop relationships of a sexual nature with each other. This also holds true for young children adopted into households with existing children.

In contrast, siblings who are raised apart sometimes develop a sexual attraction to each other when they meet later in life, developing what is known as genetic sexual attraction. Researchers on the Westermarck effect have also found that the six year old cutoff is very important; children who are raised together after the age of six do not demonstrate the Westermarck effect, indicating that it has to do with early childhood development.

Opponents of this theory often point to historical examples of sibling marriages, such as those performed in Ancient Egypt among the ruling classes. However, these marriages are not a good counterexample, because such marriages were typically contracted without consulting those involved, and it was common for children of the ruling classes to be raised separately from each other, for a variety of reasons.

In an interesting modern example of the Westermarck effect at work, researchers studied traditional Chinese families, who sometimes adopt a young girl into their households with the intention of marrying the girl to their sons. They discovered that the girls are often strongly opposed to such marriages when they come of age, and that these marriages are more prone to later dissolution, childlessness, or adultery.

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Mary McMahon
By Mary McMahon

Ever since she began contributing to the site several years ago, Mary has embraced the exciting challenge of being a WiseGeek researcher and writer. Mary has a liberal arts degree from Goddard College and spends her free time reading, cooking, and exploring the great outdoors.

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Discussion Comments
By anon940039 — On Mar 17, 2014

@ anon341051: That was the phallic stage. That's normal. It doesn't really mean you were sexually attracted. It's more like you said: a "you show me yours and I show you mine". This has nothing to do with the Westermarck effect.

By anon341051 — On Jul 08, 2013

My little sister and I suddenly felt a sexual attraction to each other at the age of ten and fourteen. This lasted a year or so. It was mostly a game of "you show me yours and I'll show you mine" and nothing irreversible was done. I often wonder why it happened. We were separated for two years when I was 6-8 because I had to go a hospital so maybe that's why this Westermarck effect didn't work for us.

By anon301190 — On Nov 02, 2012

The Westermarck effect is different for everyone, however, we all experience it in various degrees depending on our genes, meaning there are those - however small a percentage they are - who simply don't experience The Westermarck effect at all. That's the most fascinating phenomenon.

By anon81336 — On May 01, 2010

This is very interesting and I never knew that phenomenon actually had a name. For the person who asked about the kids raised together with a huge age gap larger than seven years, then the youngest one gets the implant which would still keep the two from coming together because the younger one will be grossed out by it even if the older one wasn't. So it still balances out and it's very interesting too. Yeah that was implanted genetically inside humanity for a reason!

By anon68612 — On Mar 03, 2010

This imprint or reverse imprint depending on how you look at it, explains a lot of things. But what about biological siblings raised together who are seven or more years apart in age?

I had never thought of this before, but It is also interesting to me - how very young children who get to that stage of "you show me yours and I'll show you mine." Including up to the point of "Hey! I'll let you touch mine if you want to"

I'm referring to very young playmates, three or four years old. My kids went through this, my friends kids went through this, but I don't recall ever hearing of siblings, no matter how close in age who went through this with each other. C Quinn

By anon29645 — On Apr 06, 2009

Is this an example of evolutionary psychology? An adaptation to prevent inbreeding with the possible danger of allowing the expression of harmful recessive genes? I have read that children reared on kibbutzim show that trait.

Donald W. Bales

Mary McMahon
Mary McMahon

Ever since she began contributing to the site several years ago, Mary has embraced the exciting challenge of being a...

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