Feb 20 2007

Eyes and Personality

Several readers have sent me this article on the discovery of a link between personality and the iris of the eye. The study raises several interesting concepts in biology.

The study basically shows a link between certain specific characteristics visible in the iris (the colored part of the eye) and personality. To quote the article:

“The researchers looked at crypts (pits) and contraction furrows (lines curving around the outer edge of the iris), which are formed when pupils dilate.
It was found that those with more crypts were likely to be tender, warm and trusting, while those with more furrows were more likely to be neurotic, impulsive and give in to cravings.”

The study is accepted for publication but not yet in print. To put the study in context in terms of its utility as scientific evidence, the study has found a correlation between two biological factors. Such evidence does not demonstrate cause and effect. Also, since correlations can be found randomly they are often not considered confirmed until they are replicated by later studies. Also, to be useful scientifically they must lead to a causal hypothesis that leads to predictions that can be tested. In other words – what does the correlation mean and how can we test it?

The researchers in this study do have a rather plausible hypothesis. The PAX6 gene is known to control the embryological development of the iris, and also plays a role in the development of the frontal lobes. They hypothesize that different variants of the PAX6 gene lead to either more iris crypts and a warm personality in one variant, or more furrows and greater neurosis and impulsivity in another.

If true, this is direct support for the notion that genes play a major role in determining personality. In my opinion this has been well established (see Steve Pinker’s book The Blank Slate for a good overview). Of course, environmental factors play a role, but to a different degree with different personality traits and in different individuals. But all that is necessary for a genetic link to be established is for there to be a significant trend toward one personality type with certain gene variants. It is unlikely that we will find a single gene controlling complex personality traits; it is more likely that many genes interact in a complex way. But that genes, and through them the hard-wiring of our brains, determines our basic personality structure is now an unavoidable conclusion.

The other biological fact that this study (assuming its conclusions hold up) demonstrates is that sometimes single genes control different aspects of biology or development. In this case, one gene affects the development of both the iris and the brain. This concept is useful in understanding the complexity and precise interactions of the body. It also may provide a helpful tool, in that one gene effect may be a good marker for another. In this case, the physical features of the iris may be a marker for certain personality types.

There is both potential and danger in this fact. In the hands of experience professionals, biological markers such as this can be a useful diagnostic tool. However, in the hands of the greedy and unscrupulous, they can easily be turned into pseudoscientific quack devices or tests based upon a simplistic misunderstanding of the nature of correlation. The potential for abuse is quite large. Imagine if employers started using iris screening when evaluating potential candidates. They do the same now with handwriting analysis and lie detectors. All of the complexity and subtlety of evaluating a biological marker in the context of other information and understanding the limits of such tools will be distilled down to a simple screen with definitive simple results. If the dot turns blue – do not hire this jerk.

The other potential for abuse of this kind of scientific information is in falsely claiming that it supports a pseudoscientific notion – in this case iridology. Iridology is based upon the idea the entire body is represented in the iris of the eye, and biological disorders can be diagnosed by comparing the flecks and other features of the iris to a chart. A dark fleck and 3 o’clock indicates kidney problems, for example. The idea is utter nonsense without a shred of scientific evidence. There is also no mechanism even remotely plausible to explain how so much biological information could be represented in the iris. The pathways simply do not exist.

But it is easy to see how an iridology enthusiast would misuse this study as support for the central claims of iridology. So before they even get a chance, let me debunk any such claims. First, iridology maps the iris physically to the body. Unlike phrenology (the study of bumps on the head) it does not map the iris to personality. Second, the biological marker here does not use the specific location of certain characteristics of the iris, but rather looks at the overall number of either crypts or furrows. The latter is something that can result from the genetic program that controls iris formation, the former is not. Finally, the link here is probably a specific gene that influences the development of both the brain and the iris – it is not dependent upon any informational connection between the body and the iris, as is iridology.

So this study is interesting both in what it tells us, and what it does not tell us, about the iris as a window into biology.

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