Some anthropologists and sociobiologists believe that breast fetishism derives from the breasts similarity to buttocks, but instead provide sexual attraction from the front of the body. The use of the word creampie to describe such scenes originated in U. If one person is penetrated by two objects, it is generically called double penetration . Sadomasochism is practiced in isolation relatively rarely, though some masochists report biting, pinching, or even stun-gunning themselves as a prelude to, or as part of, masturbation. Participants who exert sexual control over their partners are known as dominants or tops while participants who take the passive, receiving, or obedient role are known as submissives or bottoms. Today, religions vary in their views of masturbation; some view it as a spiritually detrimental practice, some see it as not spiritually detrimental, and others take a situational view. Once insertion is complete, the fingers are either clenched into a fist or kept straight. Contrary to the other two types, B/D does not define the Tops and Bottoms itself, and is used to describe the general activities with either partner being the receiver and the giver. Its gain in prominence has been attributed to its depiction in the film Pecker, which was released in 1998. Bukkake is a sex act portrayed in pornographic films, in which several men ejaculate on a woman, or another man. Medical pornography involves sexualized medical, often fake, including gynecological pelvic examinations, rectal examinations, and pelvic or gynecological ultrasounds. Bestiality big tit milf is illegal in many countries. In S/M, the Sadist is usually the Top and the Masochist the Bottom, but these roles are frequently more complicated or jumbled . Multiple men and women Bisexual pornography features one woman and two men who all perform hentai sex sex acts on each other. Masturbation is the self-sexual stimulation of the genitals for sexual arousal or other sexual pleasure, usually to the point hot gay sex of orgasm. Sexual orientation Pornography features an increasing variety of combinations of actors by their sexual orientation such as lesbian, gay, bisexual, and transsexuals in addition to traditional heterosexual roles.