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Psycasm is the exploration of the world psychological. Every day phenomenon explained and manipulated to one's own advantage. Written by a slightly overambitious undergrad, Psycasm aims at exploring a whole range of social and cognitive processes in order to best understand how our minds, and those mechanisms that drive them, work.

My posts are presented as opinion and commentary and do not represent the views of LabSpaces Productions, LLC, my employer, or my educational institution.

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Sunday, January 9, 2011

I have stumbled upon an interesting area of research. It seems that, like some other seemingly arbitrary measures (like digit ratios), that it has the capacity to have modest (if rough) predictive power. It also seems, at first glance, to border on the kooky side of science, and in parts reminds me of old arguments about racial intelligence and head-bumps, cranial capacity, and ol' fashioned racism.

It is the study of eye colour and its predictive power.

Eye colour is genetic (and follows Mendelian rules*), so the possibility exists that eye colour can reveal details about our genetic make-up. It's a rough-and-ready kind of measure, but like digit-ratio measures, it may serve a purpose. Data exists to suggest that blue-eyed children are more behaviourally inhibited than their brown-eyed counter-parts, blue-eyedness is correlated with infant timidity, and, may serve as a marker for social wariness (in children) (Kleisner et al, 2010). In an interesting study Kleisner et al (2010) took a bunch of photos of guys and girls, and asked subjects to rate them on a number of subjective measures. They found that brown-eyes in men were correlated with a higher dominance rating than blue-eyes (at p =.031). After controlling for age in the target-photo eye-colour remained significant (p =.05). As good scientists, they then changed the eye colour in all the photos and found that eye colour no longer predicted dominance scores. Thus, they found that males who are perceived as more dominant (i.e. having traits linked to higher testosterone) had brown eyes significantly more often. Oh, and for the record, eye-colour had no relation to attractiveness scores, but...

In a separate study it was found that blue-eyed men found blue-eyed women more attractive than brown-eyed women, and that brown-eyed men demonstrated no preference either way (Laeng, Mathisen & Johnson, 2007). What's that mechanism, and why did Kleisner et al (2010) miss it? Well, it's likely they missed it because they didn't record participant eye colour (a strange oversight). But what's the mechanism here? Is it in-group out-group stuff (as per this infamous excercise)? Apparently not. Laeng and friends (2010) argues that, given that eyes are mendelian in nature, a blue-eyed man may preferentially select a blue-eyed women because, once their child is born, blue eyes would serve as a rough indicator of paternity. If the child's eyes were brown he could be pretty sure it wasn't his. Brown-eyed men don't seem to care because there's a 25% likelihood (in any given situation) that the kid is going to have brown eyes anyway, and since there are more brown eyed men out there than there out with blue eyes...

Finally, here's a quick study before we enter the murky depths of plausibility. Suedfeld et al (2002) administered a survey to Jewish Holocaust survivors and an American Jewish control group. They found the European Jewish survivors were significantly more likely to have blue eyes and blonde hair (i.e. 'lighter' features) than the control group. They also found that male survivors had lighter eyes and hair than female survivors, and that survivors who hid from the nazi's did not different significantly either way (Suedfeld et al, 2002). This is predicated on the assumption that Jews did have darker features. I'm relying on the validity of the paper to support this assumption.

But here things get... messy.


"... it is argued that the predicted relationship between eye color and personality resulted from the higher need to be competitive in the North European climate. A competitive person is characterized by a tendency to be antagonistic, egocentric, and sceptical of others’ intentions rather than cooperative and, as such, could be expected to score low on a measure of Agreeableness. Since eye color is weakly sex-linked (Frost 2006) we do not anticipate this phenomena to still be present in only females. We argue that lighteyed people, whatever their sex, would be more competitive psychologically than dark eyed people if they are of north European descent."

- Gardiner and Jackson (2010)


I'm a little wary of the premise. They cite an evolutionary story that Northern Europeans hunted in more dangerous conditions, thus more men were hurt and killed. Women had less to forage for, and so relied on the men. So here you've got a shortage of males and the fact that the environment was so unforgiving that it was difficult for a man to provide for a great number of offspring. This lead to the assumption that men were less polygamous. Therefore, any adaptive advantage (i.e. being a kick-ass hunter, being dominant, being able to secure resources) you can convey would win you your pick of the ladies. Apparently eye-colour can do this, but not in the direction you'd expect. It has a blue-eye bias. Despite the weak link to testosterone and dominance, being blue-eyed (i.e. different) in Northern Europe you some how managed to convey greater mate-worthiness.

I'm skeptical. They only reference a book, by Frost, published in 2006, to support their just-so story. I'm thinking there might have been more rigorous methods to validate it.

So they give these Northern Europeans some personality tests. They find that, yes, blue-eyed Northerners are... less agreeable. I don't know why they didn't measure Competitiveness more directly, and they use a referenced link stating that blue-eyes and digit-ratio correlation indicate higher testosterone. If you read the link, and know about digit ratios, it's a measure of prenatal androgen exposure. I guess that's when the eyes are formed, but a lot can happen between then and adulthood.

Unsurprisingly, evidence to the contrary exists suggesting there's no meaningful correlation between eye-colour and behaviour (Elias, Nicolas & Abramson, 2008).

Personally, I'm unconvinced. It's a very poorly researched area ["eye color" = DE only gets 45 hits], and thus far, these are not very rigorous findings. My thoughts are that if you want to make a claim saying that Blue-Eyed Northern Europeans are less Agreeable than their brown-eyed counter parts, you should at least be measuring it by some objective outcome (say, criminal records?). Additionally (and this wouldn't be hard) identify the proportion of blue-eyed and brown-eyed Northerners in a matched sample comparison. If Blue-eyes were selected for, we'd see a disproportionate number of blue-eyes in the population. If it's competitiveness your after, it almost certainly correlates with something else - such as income, or sporting representation (just guessing). Despite the fact that blue-eyedness is recessive, we do have evidence to suggest it is maintained systematically by blue-eyed men. They make an excellent falsifiable prediction (both as their premise, and in their study) yet fail to rule out some of the more obvious possibilities.

Prior to that, however, is some suggestion that eye-colour does predict simpler behaviours in children. Perhaps such things hold over time...? I'm not sure, I'm skeptical, and would like to see much more research.

So what's the moral here? Eye colour has the potential to be marginally revealing about people, not in an Iridology kind of way**, but you know, in an actual way. But if you're a blue-eyed lady, my guess is you have a slightly better chance of securing a blue-eye boy than a brown-eyed boy, all other things being equal. I guess I blew my chance though, my girlfriend is brown-eyed and from an Asian country... there goes my chance at mendelian markers...


*That is, if both parents are blue, the child will be blue. If parents are mixed (blue-brown) then the child will be 1/4 blue, 3/4 brown. Blue has been found to be recessive at all grades of brown (Laeng and friends, 2007).

** Iridology basically subdivides the eye up into ~90 components, then assess the health of your organs based on some magic feature of your eye. Note to these idiots: The Iris does not change over the life-span!


Gardiner, E., & Jackson, C. (2010). Eye color Predicts Disagreeableness in North Europeans: Support in Favor of Frost (2006) Current Psychology, 29 (1), 1-9 DOI: 10.1007/s12144-009-9070-1 Kleisner, K., Kočnar, T., Rubešová, A., & Flegr, J. (2010).

Eye color predicts but does not directly influence perceived dominance in men Personality and Individual Differences, 49 (1), 59-64 DOI: 10.1016/j.paid.2010.03.011 Suedfeld, P., Paterson, H., Soriano, E., & Zuvic, S. (2002).

Lethal Stereotypes: Hair and Eye Color as Survival Characteristics During the Holocaust1 Journal of Applied Social Psychology, 32 (11), 2368-2376 DOI: 10.1111/j.1559-1816.2002.tb01867.x Suedfeld, P., Paterson, H., Soriano, E., & Zuvic, S. (2002).

Eye color as an indicator of behavior: revisiting Worthy and Scott. Psychological reports, 102 (3), 759-78 PMID: 18763448

Laeng, B., Mathisen, R., & Johnsen, J. (2006). Why do blue-eyed men prefer women with the same eye color? Behavioral Ecology and Sociobiology, 61 (3), 371-384 DOI: 10.1007/s00265-006-0266-1

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Could you also look into the timeline of development?

The shy blue-eyed children could have this stage of shying from not-known grown-ups for a longer time, or other stages also.

At least in my childhood it was a saying that blondes get into puberty, called "becoming difficult" then,  much later than darkies, and for my whole girls´ school it was true.

I do not have my paper any more, and I personally got into puberty at the exakt average age of 14 years and 8 months - being Celtic, green eyes, brown-red hair and getting sunburnt easily was also in the middle as for looks.

BUT: I do have a Celtic temper, and always had!!!

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Cool post Rift. As for the brown eyed kids.. hmm.. I was one.. and I was ridiculously shy. I was the kid who always got a note home from the teacher saying that something must be done about my shyness. I eventually grew out of it of course, and now there is no trace of that left, however, regarding this study.. I find that hard to believe.

Regarding Iridology, I don't know enough about it myself to comment, but I do have some interesting anecdotal info.. My little sister was born without her thyroid gland. They figured that out when she was 10 days old, and she's been taking eltroxin everyday to keep her healthy. She is doing great, just like anyone else w a working thyroid. In a random meeting w an iridologist however, that was the first thing she said. 'Do you have thyroid problems? Cause I could swear it looks like you don't have that gland'. I don't think their goal is to diagnose on an ongoing basis, but rather it's another way to take a overall glance at how your body works. I'm not judging one way or another, just saying that on occasion, people do get things right.

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I'm afraid I don't have the exact papers for the findings in infants, as it was cited in another paper I used. I'm guessing these effect sizes are small, and no human would be able to identify the pattern without the help of statistics. To think that a brown eyed kid behaves x or a blue eyed kid behaves y is probably going to be incorrect, but over enough individuals in the population these effects exist. It's fascinating, but it's a pretty poorly researched area, so I imagine that if further research occurs, it will be a battle-ground...

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Besides the usual correlation does not imply causation...

The problem with all this group of research is that if you do enough correlations, it's statistically certain that you will find some that are significant to the p<0.05.

This is where evidence based and science based differ. Yes, you may have some statistical basis for your hypothesis, but if you don't have the rest (biological plausibility, etc) then it is only that, a statistical result.

Would be interesting to interview their research team and look on how many clinical characteristics their team has looked at, before finding this one to publish.



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