The “Coolidge Effect”

Calvin Coolidge and his wife were being shown around a farm. Learning that a cockerel could have sex dozens of times a day, Mrs. Coolidge said to the farmer: “Perhaps you could point that out to Mr. Coolidge.” Upon being told, Mr. Coolidge asked, “Same hen every time?” “Oh no, Mr. President. A different hen each time,” the farmer replied. The President continued: “Tell that to Mrs. Coolidge.”

The Coolidge effect is a phenomenon seen in nearly every species in which it has been tested whereby males show continuously high sexual performance given the introduction of new receptive female partners.

The Red Queen by Matt Ridley, page 299.