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Dmitry Putilov
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    Dmitriy Putilov

Do women use the perceived ratio of index and ring finger lengths as a clue to man's health status rather then his aggressiveness?

Dmitriy A. Putilov, Lida Putilov

Novosibirsk State University, Psychology Faculty, Novosibirsk, Russia

Introduction. In humans, the ratio of index and ring finger lengths (2D/4D ratio) shows sexual dimorphism with men tending to have lower 2D/4D ratio compared to women. The studies initiated by Manning indicate that this dimorphism is a predictor of behavior that seems to be subject of sexual selection. It was found that the ratio is negatively associated with high testosterone levels, high achievements in sport, high scores on mental rotation test, darker skin, etc. Usually, the sexually dimorphic features (i.e. the relative sizes of breast, shoulders, hip, waist, etc.) serve as the honest signal (they are used by the members of the opposite sex as the clues to the mate quality). If the sexually dimorphic 2D/4D ratio similar to other dimorphic features in providing a clue of to mate quality (i.e. his masculinity/femininity), it can help to a young women to judge a man on his personality traits related to high testosterone levels, such as health and aggression. The first feature seems to be a definitely desired feature for a sexual partner, and the perceived ratio might serve as a clue for man's health status. However, the situation with another feature - aggression - is not so clear, because not only very low, but also very high levels of aggression would be undesired feature of a sexual partner.

Hypotheses. We hypothesized that perceived 2D/4D ratio of man's hand modulates the judgment of his health status by female subjects, but not by male subjects. We also hypothesized that women are not designed to judge the level of aggression, because the function of the preference for this feature might be too complex (i.e. U-shape). In particular, we anticipate that young women judge a hand with lower perceived ratio as belonging to healthier man, while there is no such a bias for judgment of a man's hand by a man. Moreover, we anticipate that neither women, nor men are able to judge a low perceived ratio as belonging to more or less aggressive man, because they are not searching for high or low aggression levels as desirable traits of a potential sexual partner.

Method. When someone puts his/her hand on the table and turn it to the left, the perceived 2D/4D ratio became higher. By contrast, the perceived ratio became lower, if his/her hand turned right. Using this feature, we created 5 pairs of photos of the same right hand with high and low perceived 2D/4D ratio by turning the hands of 5 men left and right. These 5 pairs of photos were shown to 30 female subjects and 30 male subjects (aged between 16 and 28) in the random order with a request to judge health status and level of aggression of these hands owners (from 1, bad health or low aggression, to 5, excellent health or high aggression). The protocol is shown in Appendix.

Results. Tables 1 and 2 of the appendix give the measurements of finger lengths on photos. They indicate that, indeed, a hand in left-turn position is looking as having lower 2D/4D ratio compared to the same hand in right-turn position. Tables 3-4 of the appendix show subjective scores for health and aggressiveness of men's hands. There is no significant difference in judgments of aggressiveness between left-turn and right-turn positions. The same is true for judgment of health status by male subjects. The only significant difference is found for females' judgments of health status. The higher heath status is associated with left-turn position (higher perceived 2D/4D ratio). The difference reaches the level of significance for the hand of the 1st man, and the similar tendency was noted for the 5th man hand. The mean difference (averaged over 5 hands) is highly significant (p=0.002).

Discussion. As we anticipated, the significant difference was found for the predicted feature (health, but not aggression) and in predicted subsample (female but not male subjects). However, the association pattern was the opposite to the anticipated pattern: higher health status is related to higher perceived 2D/4D ratio that points on lower testosterone levels. Prior to producing another interpretation of our results, they require replication (i.e. in the study of man's preference for higher 2D/4D ratio of woman's hand as reflecting her personality and reproductive traits related to higher oestrogen levels).