Coolidge Effect

The Coolidge effect is the phenomenon in which males of many species, including humans, show renewed sexual interest and responsiveness when introduced to a new female partner, even after their interest in a prior, still-available partner has waned. The effect involves both an increase in sexual responsiveness and a shortened refractory period, and researchers link it evolutionarily to polygynous mating systems in which a male's reproductive success benefits from fertilizing multiple females; the pattern has been documented across human cultures in both sexes, though it is more pronounced in males.