T The Coolidge Effect reproductive tract. Another proposed adaptive benefit of the Coolidge effect is that it allows Gavin Vance1 and Todd K. Shackelford2 males to copulate with a new female more quickly 1Oakland University, Rochester, MI, USA after finishing copulation with a previous female, 2Department of Psychology, Oakland University, as the male does not risk displacing his own Rochester, MI, USA semen from the new female. The Coolidge effect has been observed in a number of species. The first instance of this effect Synonyms was observed in rats (Beach and Jordan 1956) and has been confirmed in more recent research which Male sexual refractory period; Parental invest- showed that, in addition to a shortened refractory ment theory; Sperm competition period, male rats presented with novel sexual stimuli showed increased dopaminergic activity in the nucleus accumbens (Fiorino et al. 1997). Definition This effect has also been observed in non- mammalian species such as fish (Jordan and A phenomenon occurring in the males of some Brooks 2010), invertebrates (Steiger et al. 2008), sexually reproducing species wherein post- and hermaphroditic pond snails adopting the male copulatory sexual arousal may be reignited if the role during copulation (Koene and Ter Maat male is presented with new sexual partners. 2007). The Coolidge effect is a phenomenon observed The Coolidge effect may also extend to differ- in some sexually reproducing animals in which ential sperm allocation. Research has found evi- sexual arousal is reignited by novel sexual stimuli. dence that males of some species, such as The term was first coined by Frank A. Beach European bitterlings, will allocate sperm differen- (Beach and Jordan 1956) and refers to a story tially, such that males will produce higher-quality involving US President Calvin Coolidge and ejaculates during copulation with novel females his wife. than with familiar females (Pizzari et al. 2003; After completing sexual intercourse with a Spence et al. 2013). Because males have lower female, males will often experience a refractory obligate parental investment to produce offspring period, during which they are unable to engage in to reproductive maturity than females, males pos- sexual activity. One evolutionary explanation for sess adaptations for gaining sexual access to the refractory period is that it prevents males from females. The Coolidge effect and the differential displacing their own semen from the female’s © Springer Nature Switzerland AG 2021 J. Vonk, T. K. Shackelford (eds.), Encyclopedia of Animal Cognition and Behavior, https://doi.org/10.1007/978-3-319-47829-6_352-1 2 The Coolidge Effect allocation of sperm to novel females are examples ▶ Sexual Attraction of adaptations that facilitate male mating. ▶ Sperm Competition Some evidence for the Coolidge effect has also been observed in humans. For example, one study investigated sex differences in the desire for sex- References ual variety and found that, across cultures, men reported desire for a greater number of different Beach, F. A., & Jordan, L. (1956). Sexual exhaustion and sexual partners than did women (Schmitt 2003). recovery in the male rat. Quarterly Journal of Experi- In a more recent study, men more than women mental Psychology, 8, 121–133. expressed a greater preference for a variety of Fiorino, D. F., Coury, A., & Phillips, A. G. (1997). ’ Dynamic changes in nucleus accumbens dopamine sexual partners, regardless of the target s attrac- efflux during the Coolidge effect in male rats. Journal tiveness (Hughes et al. 2020). The same study also of Neuroscience, 17, 4849–4855. reported that men more than women have a stron- Hughes, S. M., Aung, T., Harrison, M. A., LaFayette, J. N., ger preference for their partner to frequently & Gallup Jr, G. G. (2020). Experimental evidence for sex differences in sexual variety preferences: Support change their physical appearance, whereas for the Coolidge effect in humans. Archives of Sexual women more than men reported changing their Behavior, 26,1–15. own appearance more frequently. The results of Jordan, L. A., & Brooks, R. C. (2010). The lifetime costs of this study suggest not only that men have a pref- increased male reproductive effort: Courtship, copula- tion and the Coolidge effect. Journal of Evolutionary erence for sexual variety but also that women may Biology, 23, 2403–2409. be attuned to this preference. Koene, J. M., & Ter Maat, A. (2007). Coolidge effect in While females may maximize their genetic pond snails: Male motivation in a simultaneous her- success by enforcing their ability to choose high- maphrodite. BMC Evolutionary Biology, 7, 212. Pizzari, T., Cornwallis, C. K., Løvlie, H., Jakobsson, S., & quality mating partners, males may often maxi- Birkhead, T. R. (2003). Sophisticated sperm allocation mize their genetic success by gaining sexual in male fowl. Nature, 426,70–74. access to as many partners as possible. The Coo- Schmitt, D. P. (2003). Universal sex differences in the lidge effect is one way in which males of some desire for sexual variety: Tests from 52 nations, 6 con- tinents, and 13 islands. Journal of Personality and species are adapted to copulate with a large num- Social Psychology, 85, 85. ber of females. Spence, R., Reichard, M., & Smith, C. (2013). Strategic sperm allocation and a Coolidge effect in an externally fertilizing species. Behavioral Ecology, 24,82–88. Steiger, S., Franz, R., Eggert, A. K., & Müller, J. K. (2008). Cross-References The Coolidge effect, individual recognition and selec- tion for distinctive cuticular signatures in a burying ▶ Arousal beetle. Proceedings of the Royal Society B: Biological – ▶ Sex Differences Sciences, 275, 1831 1838..