If the eyes are windows to the soul, women usually prefer average portals. That is, we're comfortable with men whose pupils -- the black bulls-eye of the eyeball -- are normal-sized. As detailed in BLONDES, we pick up on pupil size unconsciously, and the size of a person's pupils affects our opinions of his or her attractiveness and desirability.

The pupil dilates when a person is emotionally or sexually aroused. That pretty much explains why men prefer women with big pupils. And women's general preference for men with normal pupils is also explainable: we don't want men who are overaroused....and potentially out of control sexually. Unless, of course, when we want them to be.

That explains the outcome of the latest pupil-size study by Peter Caryl and his colleagues at the University of Edinburgh. The psychologists found that women who were in the fertile part of the cycles -- in particular, four days before ovulation -- had a stronger preference for large-pupiled men. Previous experiments also found that women who prefer "bad boys" had a preference for guys with big pupils. Big pupils may be part of a suite of male sexual cues -- like strong chins and aggressive behavior -- that turn women on, some more than others, and more strongly at some times than other times of the cycle.

Of course, the researchers only asked women to rate pictures of men, not actual in-the-flesh subjects. There might be a big difference. A woman likely to conceive might prefer a bulked-up, pie-eyed hunk in theory -- but in real life the oaf might send her running.