Because they're not into you? Ha, no, I don't mean when they turn their head or whole body away. I mean when their body and head remain facing you but they move their eyes away, usually up and away but sometimes straight to the side. Imagine them giggling and saying "Wellll....." -- that look. (For those who need reminding: one example, another, and another, plus the Penelope Cruz picture in the link just below.)

To continue on a previous post that discussed a hypothesis for why humans have white eyes -- to help others detect what we're looking at, and thus thinking about? -- I suggest that this reflex of girls is an amplifier of an underlying index of phenotypic quality, namely large clear eyes.

The biologist Oren Hasson (free PDFs) has proposed a distinction between two types of animal signals: "indices" are honest indicators of underlying quality, while "amplifiers" make the index easier to perceive for the recipient. As an example, if others care about your ectoparasite load, then having plumage whose color was complementary to that of the bug would amplify your signal: even from a distance, it would be obvious who was clean and who was crawling with bugs. Your spot-free or diseased plumage is the index, while its bug-contrasting color is the amplifier.

(Say, that sounds like another reason why humans evolved lighter skin when they left Africa and adopted agriculture, which introduced a huge disease burden, especially diseases that produce and/or leave behind unpleasant, visible cues. It would be easier to spot who had "good genes" here if they had light skin. This cause is likely minor, but there could be something to it.)

In the case of girly girls, their large clear eyes are the index (this is something we pay attention to when judging the attractiveness of female faces), while the looking-away reflex is the amplifier. People with larger eyes show more white than do those with beady eyes. By looking away, nearly all of the visible eye is white, making it easier for onlookers to judge eye size. It is simply easier for us to judge the area of a solid figure (the nearly all-white eye) than the sum of the areas of scraps and bits (the white parts on either side of the iris when a person is looking straight at you).

And as always, this doesn't have to be the only reason that the behavior has evolved. One alternative is that it serves to playfully tease the male by denying him eye-contact. I find that unsatisfying (the hypothesis, not teasing), since there are many ways to break eye-contact, and the most common way to do so while flirting just happens to make it easier to see what large, dreamy eyes a person has.

Labels: babes and hunks, signalling