Bondage pornography specializes in the depiction of sexual bondage or BDSM activities as photographs, stories, movies, or drawings. Concerted deployed sexual rejection exercised on the partner can be an aspect of Dominance and Submission as well. This genre also features male-on-male fellatio through a small hole made in a bathroom divider. It has since become popular enough with couples to be discussed during an episode of Sex and the City. Tentacle erotica milf fuck can be consensual, but frequently contains elements of non-consensual sex. Those with diaper-related hentai videos paraphilias differ widely in their focus of attention. Medical pornography involves sexualized medical, often fake, including gynecological pelvic examinations, rectal examinations, and pelvic or gynecological ultrasounds. Specific sex acts Anal Anal pornography features anal penetration with a penis, dildo, other objects, or some combination of them. Patricia Hill Collins, an African-American writer, theorizes that this is derived from a stereotype that those of black descent are promiscuous, and their buttocks are objectified by porn as a result. Lolita pornography caters to ephebophiles. Masturbation is the self-sexual stimulation of the genitals for sexual arousal or other sexual pleasure, usually to the point of orgasm. This type of pornography is almost exclusively hentai, as true hermaphroditic gay cock humans are not fertile and are not usually found in nature. While anal sex is commonly associated with male homosexuality, research shows that not all gay males engage in anal sex and that it is not uncommon in heterosexual relationships. A scene where many women have sex with one man is referred to as a reverse gang-bang. The loose and direct camera work often includes tight shots of the genitalia, unlike some traditional porn. Following the introduction of the Motion Picture Association of America film rating system, independent animation producers attempted to establish an alternative to mainstream animation. However, bisexual pornography is often placed near the gay section in adult video stores, since many consumers are gay men.