Theme was used to question the assumed direct effect of testosteron on men's sexual behavior. A co-occurence of testosterone peaks and sexual activity was observed more often in prospective fathers than in men who had no partner or did not want to have children with their current partner. Prospective fathers were also different from other social groups in that they had a higher frequency of patterns with monthly testosterone peaks. The observed patterns suggest that men have the ability to respond hormonally to their partner's menstrual cycle.

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