With three studies, a long lived position that women have concealed ovulation, and its possible adaptive value were investigated. In the first study, systematic changes in women across the menstural cycle were elaborated and of those, cyclic changes in the facial symmetry in regularly ovulating women were investigated. The findings showed predictable fluctuations on females' facial symmetry throughout their menstural phases. In order to determine whether the differences among the deviation from the symmetry scores of the facial pictures obtained from four menstural phases (namely, menstural, proliferative, ovulatory, and secretory phases) were detectable by males, in the second experiment, males evaluated the facial-menstural pictures for their attractiveness. The male participants rated the pictures obtained from ovulatory phases as the most attractive of all. Also they found the pictures obtained from the menstural phases to be least attractive. In the third study, half of the male participants (familiar males) rated four menstural pictures obtained from the same females, the other half of them (unfamiliar males) rated four menstural pictures, but this time each of which obtained from different females. The males in the latter group were not able to distinguish attractiveness of the facial pictures of different females. The results indicate that although there is some extent of concealment of ovulation in women as an adaptation, it is not completely concealed, especially from the familiar (or pair-bonded) males. Thus, men might have equipped with a counter-adapt, a mental device, through their evolutionary history to cope with the problem of concealment of ovulation in women by staying with her and observing the cyclic changes on her facial attractiveness.
