Relationships of smiling and flirtation to aggression and 2D:4D, a prenatal androgen index.

Smiling has been reported to be a signal of submission/lower status, or a sign of cooperation. In the present study, use of smiling and flirtation to "make people receptive to my ideas" was conceptualized as mild aggression, since it is mildly manipulative of the perception of others as to one's internal emotional status. For 91 participants (55 female, 36 male), use of smiling and flirtation to make others receptive to one's ideas were associated with relational aggression and a more male-typical (smaller) right 2D:4D finger length ratio. The only significant relationship in the male sample alone was the relationship between smiling and relational aggression. In the female sample alone, use of smiling and flirtation to "make people receptive to my ideas" was associated with a more male-typical 2D:4D finger length ratio pattern, and there was a trend for flirtation to be associated with greater physical aggression. Both 2D:4D and physical aggression have been associated with higher prenatal androgen level. It is concluded that deliberate smiling and flirtation are mild forms of relational aggression, and are related to prenatal androgenic activity in a manner similar to physical aggression. These findings are discussed in terms of the different evolutionary strategies of men and women to control their social environments.