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. Common positions include lying on back or face down, sitting, squatting, kneeling or standing. When the interest in a particular subject is obsessive, the behavior may be described as stalking. Evolutionary gay hentai psychologists suggest that rounded buttocks may have evolved to be desirable trait because they provide a visual indication of the woman youth and fertility. The warm sensation felt when urine trickles on the body seems to give very relaxing and pleasurable feelings to the person. Examples of mentally oriented practices are education games, during which the dominant requires certain forms of behavior from the submissive. Diaper fetishism is totally independent from pedophilia as the wearer derives pleasure only from the diaper and/or use of it. The industry generally refers to gay twinks such films as adult films, which is part of adult entertainment. Real medical shots or videos may violate privacy laws in some countries. The term sadomasochism is derived from the words sadism and masochism . In Japanese, this natural-fibre rope is known as asanawa; the Japanese vocabulary does not make a distinction between hemp and jute. Group sex most commonly takes place in a private sex party or semi-public swinger gathering, but may also take place at massage parlors or brothels or, in some jurisdictions, at purpose-built locations such as sex clubs. Medical pornography involves sexualized medical, often fake, including gynecological pelvic examinations, rectal examinations, and pelvic or gynecological ultrasounds. Participants who exert sexual control over their partners are known as dominants or tops while participants who take the passive, receiving, or mature milfs obedient role are known as submissives or bottoms.