Reading or viewing pornography, sexual fantasy or other erotic stimuli may lead to a desire for sexual release such as by masturbation. A spanking may be carried out with the use of a bare or gloved hand, or with any hentai sex of a variety of implements, including a paddle, strap, hairbrush, feather duster or belt. 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. A celebrity can fight the release in court to maintain deniability while still enjoying the career benefits. The genre presents itself as real couples having real sex. These actors often play the top roles but this is not always the case, such as with Kristen Bjorn and some Bel Ami models. Bondage pornography specializes in the depiction of sexual bondage or BDSM activities gay movies as porn milf photographs, stories, movies, or drawings. Concerted deployed sexual rejection exercised on the partner can be an aspect of Dominance and Submission as well. Medical pornography involves sexualized medical, often fake, including gynecological pelvic examinations, rectal examinations, and pelvic or gynecological ultrasounds. Real school shots or videos which are sexualized may violate privacy laws in some countries. Clothed female, naked male pornography features naked men and clothed women; typically, the women humiliate and abuse the men or perform fellatio and/or handjobs on the men. 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. It has since become popular enough with couples to be discussed during an episode of Sex and the City. In humans, females generally have more round and voluptuous buttocks, caused by estrogen that encourages the body to store fat in the buttocks, hips, and thighs.