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letting a good story get in the way of a few facts?

Today in the Herald I learned that eye colour can reflect personality. Apparently

[r]esearchers from the University of Queensland and the University of NSW analysed the eye colour of 336 Australians - most with a northern European background. They answered a series of questionnaires measuring aspects of their personality like agreeableness, conscientiousness and neuroticism.

The story went on to say that blue eyes were linked to competitiveness, and that this would be useful in acquiring a mate during the extreme conditions in northern Europe during the last Ice Age. Along with its own, slightly different version of the story, Medical Daily helpfully provides a link to the original paper (which is a couple of years old). The abstract (Gardiner & Jackson, 2010) tells us that

The current study investigates whether eye color provides a marker of Agreeableness in North Europeans. Extrapolating from Frost's (2006) research uncovering an unusually diverse range of hair and eye color in northern Europe, we tested the hypothesis that light eyed individuals of North European descent would be less agreeable (a personality marker for competitiveness) when compared to their dark eyed counterparts, whereas there would be no such effect for people of European descent in general. The hypothesis was tested in Australia to provide consistent environmental conditions for both groups of people. Results support the hypothesis. Implications and conclusions are discussed.

My first thought was - in extreme environments, when the whole group has to work together to survive, would a strong competitive streak really be that useful, or would cooperative behaviour be favoured? 

The survey participants were university students, & the way they were classified was interesting: 

Participants of White UK origin were classified as North European in origin (63.1%) and all other white Europeans were classified as being of Non-UK White European descent. Our designation of participants from the UK as being classified as North European and subject to the effects of the Ice Age is in-line with Frost’s (2006) theoretical account... We chose UK participants as being representative of North Europeans because we thought that its relative isolation as an island would be more likely to have led to less migration than other parts of Europe which might be more commonly defined as being part of North Europe such as the Scandinavian countries.

Yet the British Isles have a long history of migrations from Europe (going well back into prehistoric times). 

Respondents self-reported their eye colour, presumably selecting from the categories listed by Gardiner & Jackson (blue, green, hazel, brown, or black). A more objective measure would have seen photographs assessed by a third party. (It would be useful to know whether the participants knew what was being studied, as prior knowledge of the hypothesis, for example, could have biased their choices when completing the surveys.) The researchers found that 

light-eyed Europeans are less agreeable than their dark eyed counterparts

who tended to see themselves as more altruistic and helpful. Medical Daily reported that the researchers "believe the link has evolutionary roots", & the journal article bears this out. Oh goody - evolutionary psychology. I do like a good story. According to the research article, 

sexual selection was stronger in ancestral Northern and Eastern Europeans because the steppe-tundra environment of the last ice age skewed the operational sex ratio towards a male shortage. There were two causes for this shortage of males: firstly, men had to hunt over large distances in search for herds thereby often incurring injuries and dying younger; secondly, women had fewer opportunities to gather food and thus required more male provisioning, resulting in less polygyny.

Evidence, please. Evidence that men 20,000 years ago were dying off at a higher rate than women. Are sex ratios skewed, in the skeletal remains we have available from this time period? (Sex ratios tend to be slightly skewed in favour of males in modern hunter-gatherer populations such as Inuit & Australian Aborigines.) 

Also, what was that Ice Age environment really like? Up close to the kilometre-thick glaciers that pushed down from the north, conditions would have been severe, but further south? OK, there were periods when the average temperature was rather colder than now: these are the 'glacial' periods. And glacial periods were separated by 'interglacials', lasting thousands or tens of thousands of years, when things were more temperate & in fact temperatures approximated those we experience now. The 'Ice Age' wasn't one long spell of unremitting cold. Would there really have been sufficiently strong selection, for sufficiently long periods of time, to generate the eye-colour frequencies observed in modern populations? Or are we looking at the result of a bottleneck event, for example?

The article goes on to say that the supposed skewed sex ratio would have generated strong competition between women for the available men, and goes further: that because blue-eyed women are supposedly more competitive, they'd have won out and achieved more matings, spreading their genes around.

Again, evidence, please. If this proposed mechanism shaped our behaviour so strongly, well, we're only 12,000 years or so out of the last glacial period, so there would presumably still be evidence of similar sexual selection in today's populations. In fact, Gardiner & Jackson comment that 

blue eyes are still much rarer than brown and thus selection based on rare color advantage, even in the present time, may still exist in North Europe.

Somehow I doubt it: 99% of Estonians, 75% of Germans, and 90% of Danes have blue eyes. Rare colour selection, if it exists, should be in favour of brown-eyed people, in those Northern European populations.

E.Gardiner & C.J.Jackson (2010) Eye color predicts disagreeableness in North Europeans: support in favor of Frost (2006) Current Psychology 29: 1-9 doi: 10.1007/s12144-009-9070-1

Quick Personality Survey!
This cat's markings look like:

 

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4 Comments

Umm, what do red eyes say about personality? Asking for a fiend.

My first thought is the same as yours... cultures in fringe, barely-habitable environments survive specifically because people *cooperate* -- competitiveness is a luxury that is only affordable for groups living in parts of the world that are comfortable and forgiving.

My evidence for this is as strong as Gardiner & Jackson's, i.e. none.

No doubt there are sound evo-psych reasons why we both leaped to the same first thought. Perhaps we have shared ancestry.

The authors seem to be trying on two separate and mutually-incompatible arguments simultaneously. They follow Frost* in suggesting that there were two selective forces going on in parallel in northern Europe during the Ice ages: environmental pressures encouraging a more competitive disposition, and sexual selection where the ladies preferred blue eyes (resulting in a link between blue eyes and competitiveness that is coincidental). This has several flaws which you have already touched on. But at the same time, the authors also want to suggest that eye colour is linked to personality *directly* (not an outrageous idea, what with the link between fur colour and temperament in domestic animals).

It's all a bit muddled.

* A case of nominal determinism if ever there was one.

Asking for a fiend.

I saw what you did there!

Perhaps that's what you get when a psychologist and a management-school academic venture to 'try' to explain human evolution?

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