Coolidge effect

In biology and psychology, the term Coolidge effect describes phenomena seen in nearly every species that it has been tested in whereby males show continuously high sexual performance given the introduction of new receptive females (e.g. Brown, 1974 ). The sex difference that the effect refers to is explained by Bateman's principle.

Origin of the term

The term comes from an old joke according to which President Calvin Coolidge and his wife allegedly visited a poultry farm one day. 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.

"Perhaps you could point that out to Mr. Coolidge," replied the First Lady in a pointedly loud voice. 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." "Perhaps you could point that out to Mrs. Coolidge," replied the President.

Empirical evidence

The original (Beach and Jordan, 1956) experiments with rats followed the following protocol. A male rat would be placed into an enclosed large box with four or five female rats in estrus. He would immediately begin mating with all of the female rats repeatedly until eventually exhausted. Although the females would continue nudging and licking him to continue, he would not respond. However, if a novel female were introduced to the box he would become alert and find the ability to mate once again with the new female. This phenomenon, which has been termed the Coolidge Effect, is not limited to Rattus norvegicus (Wilson, Khuen, Beach, 1963). It is attributed to an increase in dopamine levels and its subsequent effect upon the limbic system.

While the Coolidge effect is usually seen demonstrated by males (that is, males displaying renewed excitement with a novel female), Lester and Gorzalka came up with a model to see if the Coolidge effect occurs in females also. They used hamsters instead of rats, and the results showed that it does occur in lesser degrees in females.

Some researchers think that exposure to the pheromones of a new female is a significant factor in this phenomenon.

The Coolidge effect has sometimes been mentioned as an explanation of why pornographic images are exciting to the male when first purchased, but after repeated viewing can "lose its effect". The phenomenon may also explain why male pornographic actors may use the services of a fluffer.

See also

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