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.

Peace, Love, and Pit Bulls – What Your Choice of Dog Says About You as a Person

December 11, 2012
Not at all as aggressive as the dreaded Chihuahua.

Not at all as aggressive as the dreaded Chihuahua.

The term Pit Bull usually refers to the American Pit Bull Terrier, the Staffordshire Terrier, and the American Staffordshire Terrier. They all share certain typical characteristics, such as an athletic build, large jaw, and muscular neck.

Are they vicious freaks? The breed as such does not display any typically aggressive behavior. Research show that other dogs like Chihuahua and the Dachshund are much more aggressive. And yet statistics from CDC show that Pit Bulls kill by far more than any other dog breed. How can this be?

Well, for one, the Pit Bulls are strong so that when they do attack they can do more damage than Chihuahuas or a Dachshunds.

But perhaps more importantly, Pit Bulls attract a certain type of owners who contribute to the problem. Several studies have shown this. In 2006 one study published in Journal of Interpersonal Violence looked at 355 dogs of high and low risk profile. The high risk dogs are those common in fatal attacks, mainly Pit Bulls, making up 92 percent of the sample, but also Rottweilers and some other breeds. They found a clear overrepresentation of criminal convictions among owners of high risk dogs for things like assault, domestic violence, endangering children, and illegal possession of drugs and weapons.

This could be seen as a social marker but other studies have examined the personality traits of high risk dog owners. In 2009, one study published in Journal of Forensic Science found that these owners score high on the traits primary psychopathy and sensation seeking. Another study that followed up on that study in the same journal interviewed 754 college students about their dogs and their personality, thoughts, and behavior. It found a similar pattern of antisocial tendencies. These traits are highly inheritable and resistant to environmental influences. So it’s not a social marker but a matter of personality.

And that is why you should be cautious when you encounter a Pit Bull. While the breed has a good temperament and some owners are responsible, the combination of anatomy and ownership profile makes for a dangerous dog. This is no doubt why liability insurance costs so much for these dogs, and why many companies refuse to insure Pit Bulls. The insurance companies are disinterested in the debate; they must be competitive and just look at the risk and the bottom line.

In a way this is obvious. I mean, even if you don’t believe in the statistics and the research, no one can deny that these dogs are feared by many. So who wants a dog that will scare people? Exactly those that are identified in the research – individuals scoring high on sensation seeking and psychopathy. People who think a Pit Bull would be exciting to own and who don’t have much empathy with others.

Why Intelligent People Are Healthier

November 29, 2012

“If you ask what is the single most important key to longevity, I would have to say it is avoiding worry, stress and tension. And if you didn’t ask me, I’d still have to say it.” George Burns (1896-1996)

The studies on intelligence and longevity all agree that those with high IQs live longer. One of these studies, the Swedish Conscript Study, is especially impressive since it includes practically all Swedish men born between 1950 and 1976 – making the number of participants just under one million. They all took an intelligence test which uses a nine grade scale. Those scoring 9 were 20 years later shown to have a 70 percent less risk of mortality than those scoring a 1.

This may sound like something obvious – people with high intelligence come from better homes and have been brought up by parents who give them more fruit and vegetables and less pizza and soft drinks. However, it was shown that adjusting for things like parental socioeconomic status as well as blood pressure, weight, physical illness at conscription, the risk of mortality for those with the highest intelligence was still reduced by 60 percent compared to those with the lowest intelligence. This is really worth noticing – social background makes up less than 10 percent of the reduced risk of mortality. This is partly explained by the fact that the men were in their 40s at the follow-up, and few die from cardiovascular disease at that age. But it’s still interesting to note that social background is such a little factor in overall mortality.

So while it’s known that intelligent people engage in health behaviors – eating vegetables, exercising, following the doctor’s orders when ill. It’s reasonable to suspect that a healthy lifestyle is the mediator between IQ and longevity, even though this lifestyle is probably more a matter of personal decision than upbringing. It accords well with the connection between IQ and death in cardiovascular disease, the biggest killer. But if we look at cancer, the second biggest killer, the connection with intelligence is weak or non-existent. For skin cancer it’s even inversed. How can that be?

I haven’t found any explanation for this paradox in the literature, but looking at the causes of these two killers it’s clear that cardiovascular disease is related to stress in a way that cancer is not. And stress is a lot about lack of control. It’s a well-known fact that those prone to stress, that is those having the trait neuroticism, have more heart disease. This idea is supported by another large study, called the Vietnam Experience Study, which looked at mortality of veterans and found that the more neurotic a veteran was the more a high intelligence would lower his mortality.

This suggests that a major part of why intelligence promotes health is in that it protects against the harmful effects of stress and thus against cardiovascular disease. How? It could be that they use their intelligence to cope with stressful events better. It may also be a matter of what some researchers call system integrity. A high intelligence, according to this theory, is an indication of a  generally more robust and well built organism that doesn’t break under pressure as easily as the average. Although this has been hard to prove some studies have found that reaction time, as a proxy for system integrity, account for most of the correlation between intelligence and mortality. It could of course also be a combination of stress handling ability and system integrity.

All of these interesting findings are found in the relatively new field of cognitive epidemiology. While it doesn’t disprove that eating lots of vegetables is good for you (it really is) it shows that this may be of less importance than most of us imagine compared to stress – our proneness to it in form of neuroticism, but perhaps even more important how we cope with it, both psychologically and in terms of biological hardiness.


Is Testosterone and Social Mobility Causing Anorexia in Women?

August 27, 2012

You can never be too skinny or too rich. Nancy and Henry Kissinger.

A recent study published in Personality and Individual Differences 51 (2011) showed a link between prenatal testosterone levels (as measured with the ratio between the second and fourth finger) and anorexia.  Why would that be?

Earlier, several studies have found that men as well as women with high levels of testosterone react with stress specifically when their social status is in jeopardy and they become very eager to regain their status.

But social status is not the same for men and women. Traditionally, but also in present time, men measure status in terms of social dominance and power. Women, on the other hand are more likely to assert themselves by weight control. Because from an evolutionary standpoint women haven’t had much power other than that of attracting the powerful male. And one way to do that is to look good and stay in shape.

The question is how normal weight control can turn into anorexia. I think this relates to how modern society clashes with our evolutionary nature. As a species, we have lived most of our time in small groups that have been relatively equal. People have always fought to climb the social ladder and to maintain their positions. But modern society has enormous class differences. So anyone high testosterone person in the upper part of the hierarchy can now fall so much further down, even lose their place in it altogether.

This explains why white women are more anorectic than women of other races, and why women from the upper class or upper middle class are more affected than lower classes. They are the ones who are highest in the hierarchy so they are most likely to end up in a situation in which they feel their status is being threatened. And in today’s society, social mobility makes this threat more realistic than ever. This increased threat from the modern environment probably makes some of these high testosterone women go overboard in their attempt to maintain their status. They lose perspective on things and their genetic programing gets the better of them.

This is just a theory of course proposed by the late Linda Mealy and others. But it makes sense in light of this study. And it makes a whole lot more sense than conventional wisdom of how it’s the media or the fashion industry or evil men who pressure women to lose weight. Any part of those industries with an agenda to change women rather than to make money would be outcompeted. And men are horny, regardless of where in the social hierarchy they are. They would not pressure women into becoming something they found sexually repulsive.

So that’s why Henry Kissinger, who once proclaimed that power makes a man sexy,  judging by the picture above, thought skinny does the same for a woman.

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