Coolidge effect

In biology and psychology, the term Coolidge effect describes a phenomenon—seen in nearly every mammalian species in which it has been tested—whereby both males and females exhibit continuous high sexual performance given the introduction of new receptive partners.

The term comes from an old joke, according to which U.S. President Calvin Coolidge and his wife allegedly visited a poultry farm. During the tour, Mrs. Coolidge inquired of the farmer how his farm managed to produce so many fertile eggs with such a small number of roosters. The farmer proudly explained that his roosters performed their duty dozens of times each day.

"Tell that to Mr. Coolidge," pointedly replied the First Lady.

The President, overhearing the remark, asked the farmer, "Does each rooster service the same hen each time?"

"No," replied the farmer, "there are many hens for each rooster."

"Tell that to Mrs. Coolidge," replied the President.