Nipple stimulation

At puberty, the male's breasts remain rudimentary but the female's develop further, mainly due to the presence of estrogen and progesterone.

[5] The stimulation of women's nipples from suckling, including breastfeeding, promotes the production and release of oxytocin and prolactin.

[11] Nipple erection is due to the contraction of smooth muscle under the control of the autonomic nervous system,[12] and is a product of the pilomotor reflex which causes goose bumps.

[14][15][16] In Patterns of Sexual Behavior, a 1951 analysis of 191 traditional cultures, the researchers noted that stimulation of the female breast by the male before sex "seemed absent in all subhuman forms, although it is common among the members of many different human societies.

A recent psychological study found that the presence of nipple erection can influence people's views of a woman's intelligence, morality, and sexuality.