Men who, for the purposes of the study, were considering just a fling with a woman were more likely to peek at a picture of her body than men who were thinking about a long-term relationship, the research found. The guys considering a long-term relationship showed a preference for looking at her face.

　　The findings may reflect men's evolutionary drives, said study co-author Jaime Confer, a psychology graduate student at the University of Texas in Austin. Men who want a fling, she said, may be subconsciously looking to a woman's waistline to judge the woman's current fertility. Men looking for long-term partners, on the other hand, may be more interested in her face for clues of reproductive potential in the future.

　　Previous studies have noted that a woman's face reflects her youth and health, which can affect her future reproductive abilities. Lots of wrinkles might suggest she has few childbearing years left, for example. The body, on the other hand, holds clues as to how fertile a woman is right now. Waist-to-hip ratio can signal whether a woman is already pregnant, and maybe even whether she is currently ovulating, according to previous research.

　　Confer and her colleagues asked 192 men and 183 women, all heterosexual and in college, to consider entering into either a short- or long-term heterosexual relationship. The students were given a masked picture of a potential date, with boxes covering both the head and clothed body. They could choose to remove either the box covering the head or the box covering the body, but not both.

　　On the whole, 61 percent of men and 69 percent of women chose to see the individual's face. But among the men who were thinking short-term, the interest in viewing the woman's face decreased. Of the men considering short-term relationships, 52 percent chose to see the body.