Mammary intercourse has sometimes been considered a perversion. A study of the condom usage habits of New Zealand sex workers said that they offered various safe sex alternatives to vaginal sex to clients who refused to wear a condom. The primary subjects of pornographic depictions are pornographic models, who pose for still photographs, and pornographic actors or porn stars, who perform in pornographic films. Commenting on why there are not as many female gay cock macrophiles, psychologist Helen Friedman theorized that because women gay hentai in most societies already view men as dominant naked milf and powerful, there no need for them to fantasize about it. They may regard it as an enhancing element of their sex lives or as their primary form of sexual activity. As well as traditional attraction, the topic also incorporates feederism and gaining, where sexual gratification is obtained via the process of gaining body fat. Lesbian pornography typically features a wider range of appearances and body types than is typical of mainstream pornography. This genre also features male-on-male fellatio through a small hole made in a bathroom divider. The warm sensation felt when urine trickles on the body seems to give very relaxing and pleasurable feelings to the person. People may experience pleasure from anal sex by stimulation of the anal nerve endings, and orgasm may be achieved through anal penetration – by indirect stimulation of the prostate in men, indirect clitoral/G-spot stimulation in women, and associated sensory nerves . 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. 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.