Breasts play a substantial role in female sexual pleasure. When nipples are full of nerves, during an MRI study, it was found that stimulating the nipple lights up the same part of the brain that is linked to the genitals. A study carried out, reported that touching the nipples/breasts causes or enhances sexual arousal in approximately 82% of young women. When aroused, a woman’s breasts can swell to up to 25% of their normal size, and become more sensitive. Stimulating the nipples releases neurochemicals like; Dopamine and Oxycontin. This in turn causes the vagina to swell and lubricate.
There is far less study on the importance of nipple use for men, however one piece of research done in 2006 reported that 52% of men get aroused by nipple play.