The permanently enlarged human breast is a peculiarity of our species. Most likely, it evolved as a sexual signal communicating fertility (1).
The sexual signal theory is supported by the importance of breasts in physical attractiveness. Their use in pornography points to the same conclusion.
Yet, it is worth noting that breasts are far less eroticized in forager societies where women go topless and use their milk-producing organs to feed babies. In such societies, breasts are denigrated as utilitarian and unromantic. They are spoken of as milk containers.
Even amongst foragers, breasts are not entirely lacking in sexual significance. According to anthropologists (2) the breasts are generally stimulated in foreplay around the globe.
Moreover, the breasts play a key role in female sexual arousal. In their classic report on the female sexual response, Masters and Johnson (3) pointed out that breast volume increases during sexual arousal.
That observation would be difficult to explain if the breast served purely as a visual signal. After all, it would make more sense if the breast reached maximum size while still attracting a mate and before copulation has begun.
Indeed, the phenomenon leads one to suspect that men are not the only ones who like breasts. Women also derive a great deal of satisfaction from them and this is not just from their use as a visual stimulus that manipulates men whether in the real world or in the fantasy kingdom of pornography, exotic dancing, and "entertainment."
Beneath the surface interesting events are taking place. Stimulation of the nipple that occurs during breast feeding increases the amount of the hormone oxytocin that circulates. Oxytocin is often referred to as the "cuddling hormone" because it is released by male and female mammals during close social encounters of various kinds (4).
In addition to its general social effects, whereby a mother feels closeness for the baby she is feeding, there are other more specialized functions. One is that milk flows, a reflex known as the "milk let-down response" familiar to mothers and dairy farmers alike. Another - you guessed it - is orgasm. Indeed, some women report experiencing their first orgasm, not from genital stimulation, but from breast feeding.
Contrary to Jena Pincott's recent post, neuroscientist Larry Young's view that breast stimulation enhances heterosexual bonding does not seem so far fetched. Men are not the only ones who are mad about mammaries. Women love them too.
1. Barber, N. (1995). The evolutionary psychology of physical attractiveness: Sexual selection and human morphology. Ethology and Sociobiology, 16, 395-424.
2. Ford, C. S., & Beach, F. A. (1951). Patterns of sexual behavior. New York: Harper.
3. Masters, W. H., & Johnson, V. E. (1966). Human sexual response. Boston: Little Brown.
4. Uvnas-Moberg, K. (1998). Oxytocin may mediate the benefits of positive social interaction and emotions. Psychoneuroendocrinology 23: 819-835.