Coolidge Effect
A biological phenomenon in which an animal shows renewed mating interest when introduced to a new partner, even after losing interest in a previous one — observed across many species.
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Origin
Behavioral endocrinologist Frank A. Beach coined the term around 1958, naming it after a famous joke about President Calvin Coolidge. In the anecdote, Mrs. Coolidge tours a farm and remarks on a rooster's prolific mating; when told "a different hen every time," the President replies, "Tell that to Mrs. Coolidge." Beach and colleague Lisbeth Jordan had studied the phenomenon in rats in 1955, observing that males who had reached exhaustion with one partner would resume mating immediately upon introduction of a new one.
Updated February 22, 2026