Ivory Towers: Taking a nose at face value

ONE of the things people are good at is telling the difference between male and female faces, yet the cues we use to discriminate are so subtle that we cannot tell how we do it, particularly when beards and lipstick are absent. Two recent papers in Perception (1993, vol 22) throw a little light on the subject.

In Sex Discrimination: how do we tell the difference between male and female faces, the researchers investigated the role of the eyes, nose, chin, eyebrows, skin texture and other features in a photograph on people's ability to assess the gender of the subject. In the follow-up paper - What's the difference between men and women? Evidence from facial measurement - measurements of facial features were analysed to see what separates the sexes.

Earlier research on the topic had shown that in judging the gender of photographic subjects, eyes are more important than mouths, and mouths are more important than noses. But full-face photographs may tend to underestimate the contribution of nose protuberance. However, they first wanted to eliminate cosmetic aids, so 88 female and 91 male adults were photographed, full face, neutral expression, no make-up and with swimming caps concealing hair. Respondents still correctly judged gender in 96 per cent of cases. Most errors were in judging female faces as male.

Further experiments were conducted with chins, noses or eyes masked, or with laser-scanned pictures obscuring details of skin texture. They also saw if it made a difference seeing photographs upside-down. Finally, they used computer images to manipulate features to see what effect changing nose shapes had. While individual features certainly contributed towards gender assessment, masking any single one of them did not produce any dramatic decrease in performance. Using laser-scanned pictures to reduce textural and three-dimensional cues resulted in considerably more errors.

Turning the picture upside-down also produces errors. Research in 1987 showed one circumstance in which seeing things inverted can be an advantage: composite photographs were made from pictures of celebrities by joining the top half of one face to the bottom half of another. Subjects were better at identifying the celebrities when the pictures were viewed upside-down. Inversion disrupts the process of configural processing making it harder to see the picture as a whole face. If you want to see it as a whole, it is easier the right way up; if you want to separate the two halves, look at it upside-down.

All the evidence seems to suggest that face recognition and gender assignment is a highly complex procedure using all available cues and the relationships between them. The mathematical analysis, however, did confirm that men's noses stick out further, while women have larger cheeks.