Solving a Mystery for Satoshi Kanazawa

February 14, 2013

Over at the Big Think, psychologist Satoshi Kanazawa lists what he considers the unsolved mysteries of evolutionary psychology. One of these mysteries is the question of why people with many siblings have many children. According to Kanazawa this doesn’t make any evolutionary sense at all,

This is because people with many siblings have the option of investing in their younger siblings and increasing their reproductive success by doing so.  Humans are just as genetically related to their full siblings as they are to their own biological children; both share half their genes.

I think the solution to this mystery can be found in viewing extraversion and introversion as evolutionary strategies. There is plenty of research showing that extraverts are more sexually active than introverts. This would lead to them having more children (we’re dealing with an evolutionary time scale so we can ignore the effect of contraception), and since it’s also a highly inheritable trait it would make a person with many siblings more likely to have extraverted parents and for that reason he is likely to have inherited their extraversion and have many children himself.

But if so, why aren’t we all extraverts – if it’s enables us to spread our genes so well? To understand this I think we need to look at differences in this trait between people living in environments with varying degrees of resources. In good times with plenty of food available, extraverts would propagate and spread their genes by having many children but a relatively small parental investment. But sooner or later hard times would come and then the introverted strategy of few children and high parental investment would pay off. If there is a scarcity of food, giving all you can spare to one child rather than sharing it between 4-5 children becomes a winning strategy. That way, hard times would ensure that genes for introversion would survive.

Now, it’s a fact that different regions vary in resources. People who have originated in a cold climate, or at least in a region with long cold winters should, if this theory is correct, have a higher level of introversion than people from warmer regions. We are all familiar with the stereotypes of the introverted northerners and extraverted southerners. Is there any truth in it?

Looking at extraversion scores from Richard Lynn’s study (1995) of 36 (I omitted Iceland because it has a microscopic population) nations there is actually a bit of a pattern supporting the theory.

The average level of extraversion for all countries was 18.4. But those who originated in a cold climate (Nordic or Central Asian) averaged at 17.2, while those originating in a warm climate averaged at 20.0, with intermediary countries averaging at 17.9.

Extraversion scores by country and climatic origin.

Extraversion scores by country and climatic origin.

I’m probably not the first person to have this idea but since Kanazawa insists that it’s a mystery and this seems to be a plausible explanation, I thought I should share it.


Can You Tell What a Person Is Like Just by Looking at Him?

November 13, 2012

It seems unlikely but there is a lot of research that illustrates that most people can assess someone’s personality based on very little information. A photograph, an office, bedroom, a personal website have all shown to be sufficient to achieve a better than random result in guessing personality as well as sexual orientation.

A German study on this (Borkenau 2009) found that just seeing a headshot of someone for 50 milliseconds was enough to assess extraversion. In order to find out how the participants were able to spot this trait, Borkenau and his colleagues had a second group look for visual characteristics in the headshots. It turns out the people who were rated as extraverted looked more cheerful and smiled more than others. This makes sense since a lot of research has found that extraverts actually are more cheerful than introverts.

While spotting extraversion by looking at a picture for 50 milliseconds may sound impressive, it’s probably not. Thing is, the study looked at all the five traits included in the popular Big Five model of personality – Extraversion, Neuroticism, Agreeability, Openness to Experience, and Conscientiousness. And the participants only got one right. So why did they get any right at all?

The answer may be found in how they got the others wrong. It turns out that the people with headshots showing cheerful and smiley faces were all considered to be extraverted, low on neuroticism, and high on agreeableness. These traits are all socially desirable. In other words, they attributed socially desirable traits to people who looked cheerful. And as it happens, extraverts generally report feeling happier than introverts so they probably smiled more – but that appears to have been just a happy accident.

This study suggest that people make judgments based largely on wishful thinking. They see a person who is smiling and they assume that he or she is what they consider a pleasant person. Social psychologists have shown this phenomenon numerous times; people look at conspicuous information, like a broad smile and ignore the less obvious information, like that the person in question is being photographed so he may be smiling even if he isn’t that cheerful or he may not be smiling because something caught his eye.

They way to assess someone’s personality is not by “speed reading”, it’s by long-term observation. To look at how people behave when you are familiar with the situation, to gather lots of data and see patterns emerge. If you thinks someone is pleasant because they smile it only means you’re an easy target for sales people.


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