People can tell a woman's age by the evenness of her facial skin color, even when other visual cues are absent. So say a team of researchers at the University of Göttingen who photographed the faces of 170 women from 11 to 76 years of age and altered the photos to remove all other signs of aging—facial furrows, folds, lines, and wrinkles. Only one sign remained: uneven skin color. The photos were then shown to 198 male and 232 female subjects who had to estimate each woman's age, as well as her perceived healthiness and attractiveness.
- Evenly colored faces were judged to be younger, healthier, and more attractive. Faces with uneven color were judged significantly older.
- The correlation was high between actual and estimated age (r=.708).
- This task was considered significantly easier by men than by women.
The authors conclude that "skin color distribution, independent of facial form and skin surface topography, seems to have a major influence on the perception of female facial age and judgments of attractiveness and health" (Fink et al. 2006).
Fine. But just one thing. Do we learn to use this visual cue through observation? Or do we clue into it because of some inborn predisposition? This question seems to be the study's starting point. The abstract tells us that "preferences for facial characteristics … may reflect adaptations for mate choice because they signal aspects of mate quality." What is an adaptation? It is a heritable trait favored by natural selection. Yet, having mentioned the 'a' word, the authors go no further—not even in their suggestions for further investigation.
It's not as if they couldn't have gone further. For instance, the male subjects evaluated evenness of female skin color more easily than the female subjects did. Is this sex difference hormonally mediated? Do men perform this task more easily if they have high testosterone levels? Less easily if they have low testosterone levels? Does task performance vary in women with the menstrual cycle? What about prepubertal children?
To be fair, this study is no worse than many others in evolutionary psychology. A typical E/P study will show that people behave adaptively in such and such a situation and a typical reader will come away thinking that the behavior must be an evolutionary adaptation. Yet such an impression is hardly warranted by the evidence. It may not even be intended by the author. But if it is unintended, just what is the reader supposed to think?
Fink, B., K. Grammer, and P.J. Matts. 2006. Visible skin color distribution plays a role in the perception of age, attractiveness, and health in female faces. Evolution and Human Behavior 27:433-442.