A pornographic work is characterized as hardcore if it has any hardcore content, no matter how small. Although interracial pornography theoretically can apply to depictions of sexual activity between performers of any different racial groups, the term is most commonly used for heterosexual naked milf sex acts between black and white performers. A survey by the New York City Department of Health and Mental Hygiene found that heterosexual women are more likely to bareback when engaging in anal sex than homosexual and bisexual men. In human sexuality, a threesome is sexual activity that involves three people at the same time. Mammary intercourse is said by Alex Comfort to produce mutual orgasm hentai sex in women with sensitive breasts , and hot gay sex it was one of the nine substitute exercises for penetrative sexual activities, as detailed in the Paradis Charnels of 1903. A sex party is a gathering at which sexual activity takes place. Adult animation is genre of animation geared towards adults and sometimes teens. The term lesbian is also used with regard to sexual identity or sexual behavior, regardless of sexual orientation, or as an adjective to characterize or associate nouns with female homosexuality or same-sex attraction. It is commonly depicted in pornography, but very rarely in mainstream cinema. Ass to mouth pornography shows the transfer of a performer penis from a second performer anus to that same second performer mouth in a single shot. A homosexual threesome would involve either three men or three women. Mutual masturbation can be practiced by males or females in pairs or groups with or without actually touching another person as indicated by the following examples of contact versus non-contact scenarios: Non-contact mutual masturbation Two people masturbating in the presence of each other but not touching. Although pornography has usually focused on heterosexuality, due to the prevalence of the heterosexual orientation, explicit gay material has a long history as well, which reaches back to Greek antiquity, if not to prehistory.