Masturbation is the self-sexual stimulation of the genitals for sexual arousal or other sexual pleasure, usually to the point of orgasm. 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. The name was coined from the title of the controversial book. Pornography is often distinguished from erotica, which consists of the portrayal of sexuality with high-art aspirations, focusing also on feelings and emotions, while pornography involves the depiction of acts in a sensational manner, with the entire focus on the physical act, so as to arouse quick intense reactions. Both sexes sometimes apply lubricating substances to intensify sensation. Transgender pornography features performers who cross-dress for sexual gratification, either for themselves or for their partners. A study of 164 males in Finland from two SM clubs found that 18.2% had engaged in coprophilia; 3% as a sadist, 6.1% as a masochist, and 9.1% as both. 18% of heterosexuals and 17% of homosexuals in the study pool had tried coprophilia, showing no statistically significant difference between heterosexuals and homosexuals. The cover can have hinges or be a separate part. Concerted deployed sexual rejection exercised on the partner can be an aspect of Dominance and Submission as well. Point of view gay hentai pornography is adult entertainment filmed to look as if the watcher videos gays were experiencing the sex act themselves. Oral sex pornography frequently features a person performing fellatio, and less frequently cunnilingus. A woman can use a secondary vibrator, between the dildo and her genitals, to get pleasure momporn from pegging. Many cultures describe pain as an aphrodisiac. Foot fetish pornography features heavy emphasis on the feet of the participants, either in combination with kissing and genital sex or in the context of acts such as trampling or crush fetishism. Some may keep their hand stationary while pumping into it with pelvic thrusts in order to simulate the motions of sexual intercourse.