Coolidge effect

In biology and psychology, the Coolidge effect is a phenomenon—seen in nearly every mammalian species in which it has been tested—whereby males (and to a lesser extent females) exhibit continuous sexual activity if they are introduced to receptive sexual partners,^[1][2][3][4] but will eventually stop having sex if the partner has already been copulated with.

Origin of the term

Ethologist Frank A. Beach is credited with naming the "Coolidge effect" in 1955, after one of his students suggested the term at a psychology conference.^[5] He attributed the neologism to:^[5]

… an old joke about Calvin Coolidge when he was President … The President and Mrs. Coolidge were being shown [separately] around an experimental government farm. When [Mrs. Coolidge] came to the chicken yard she noticed that a rooster was mating very frequently. She asked the attendant how often that happened and was told, “Dozens of times each day.” Mrs. Coolidge said, “Tell that to the President when he comes by.” Upon being told, President asked, “Same hen every time?” The reply was, “Oh, no, Mr. President, a different hen every time.” President: “Tell that to Mrs. Coolidge.”

The joke appears in a 1978 book (A New Look at Love, by Elaine Hatfield and G. William Walster, p.75), citing an earlier source (footnote 19, Chapter 5).[1]

Empirical evidence

The original experiments with rats applied the following protocol:^[6] A male rat was be placed into an enclosed large box with four or five female rats in in heat. He immediately began to mate with all the female rats again and again until eventually, he became exhausted. The females continued nudging and licking him, yet he did not respond. When a novel female was introduced into the box, he became alert and began to mate once again with the new female. This phenomenon is not limited to common rats.^[7] The Coolidge effect is attributed to an increase in dopamine levels and the subsequent effect upon an animal's limbic system.^[8]

Human males experience a post-ejaculatory refractory period after sex. They are temporarily incapable of engaging in sex with the same female after ejaculation and require time to recover full sexual function. In popular reference, the Coolidge effect is the well-documented phenomenon that the post-ejaculatory refractory period is reduced or eliminated if a novel female becomes available.^[9] This effect is cited by evolutionary biologists as one reason why males are more likely to desire sex with a greater number and variety of partners than females,^[9] though of course sometimes human females are known to copulate with multiple and novel partners as well.

While the Coolidge effect is usually seen demonstrated by males—that is, males displaying renewed excitement with a novel female—Lester and Gorzalka developed a model to determine whether or not the Coolidge effect also occurs in females. Their experiment, which used hamsters instead of rats, found that it does occur to a lesser degrees in females.^[3][4]

On simultaneous hermaphrodites

A 2007 study focusing on the Coolidge effect in simultaneously hermaphroditic species confirmed the validity of the Coolidge effect in freshwater snail Lymnaea stagnalis.^[10] Biomphalaria glabrata, another simultaneous hermaphrodite freshwater snail, does not exhibit sex-specific effects of partner novelty, and thus there is no Coolidge effect in the species.^[11]

See also

• Bruce effect

References

1. ^ Reber, A. S. & Reber, E., The Penguin dictionary of psychology (3rd ed.), London: Penguin, ISBN 0140514511 
2. ^ Brown, R. E. (1974), "Sexual arousal, the Coolidge effect and dominance in the rat (Rattus norvegicus)", Animal Behaviour 22 (3): 634–637, doi:10.1016/S0003-3472(74)80009-6 
3. ^ ^{a b} Lester, GL; Gorzalka, BB (1988), "Effect of novel and familiar mating partners on the duration of sexual receptivity in the female hamster", Behavioral Neural Biology 49 (3): 398–405, PMID 3408449 
4. ^ ^{a b} Pinel, John (2007), Biopsychology (6th ed.), Boston: Pearson Allyn and Bacon, ISBN 0205426514 
5. ^ ^{a b} Dewsbury, Donald A. (2000) "Frank A. Beach, Master Teacher," Portraits of Pioneers in Psychology, Volume 4, p269-281
6. ^ Beach, F. A. & Jordan, L. (1956), "Sexual Exhaustion and Recovery in the Male Rat", Quarterly Journal of Experimental Psychology 8: 121–133 
7. ^ Wilson, J; Kuehn, R. & Beach, F. A. (1963), "Modifications in the Sexual Behavior of Male Rats Produced by Changing the Stimulus Female", Journal of Comparative and Physiological Psychology 56: 636–644 
8. ^ Fiorino, D. F.; Coury, A. & Phillips, A. G. (1997), "Dynamic Changes in Nucleus Accumbens Dopamine Efflux During the Coolidge Effect in Male Rats", Journal of Neuroscience 17 (12): 4849–4855, http://www.jneurosci.org/cgi/content/full/17/12/4849 
9. ^ ^{a b} Hergenhahn, B. R.; Olson, Matthew H. (2003), An introduction to theories of personality, Upper Saddle River, N.J.: Prentice Hall, pp. 396–397, ISBN 0130992267 
10. ^ Koene J. M. & Maat A. T. (6 November 2007) "Coolidge effect in pond snails: male motivation in a simultaneous hermaphrodite". BMC Evolutionary Biology 7: 212. doi:10.1186/1471-2148-7-212
11. ^ Häderer I. K., Werminghausen J., Michiels N. K., Timmermeyer N. & Anthes N. (12 October 2009) "No effect of mate novelty on sexual motivation in the freshwater snail Biomphalaria glabrata". Frontiers in Zoology 66: 23. doi:10.1186/1742-9994-6-23.