Mats Larsson, a psychology graduate student at Örebro University in Sweden has linked iris patterns to personality traits. Larsson took photos of 428 volunteers’ eyes and administered a standard personality test. He then counted the frequency of crypts (squiggly lines radiating out from the pupil) and furrows (circular lines curving around the outer edge of the iris). He found that a low frequency of crypts was significantly associated with tender-mindedness, warmth, trust, and positive emotions, whereas more distinct and extended furrows were associated with impulsiveness.
His results might seem strange, but Larsson notes that earlier studies have tenuously linked darker eyes to higher scores on extroversion, neuroticism, and sociability, although the effects seem to fade after early childhood. And, he adds, brain and eye development are closely linked in utero, so the appearance of distinctive eye traits might well be related to patterns of brain differences. For example, Larsson points to a gene called PAX6, which controls iris tissue growth. Intriguingly, mutations in PAX6 have also been linked with high rates of unusual behavior, including poor impulse control and abnormalities in associated brain structures, like the left cingulate cortex. Still, cautions Larsson, looking deep into people’s eyes won’t give you irrefutableinsight into their personality. “We’ve only looked at group effects,” he says. “It’s not possible to describe an individual’s personality from our data.”