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. Interactive pornography, available in CD-ROM and DVD format, allows the viewer to select the particular acts performed at any one time, sometimes with the camera providing a first person view. Mammary intercourse is known as titty-fucking, titfuck, or a titjob in the United States, as well as tit wank or French fuck in the United Kingdom - the latter term dating back to the 1930s; while a more jocular equivalent is a trip down mammary lane. Transgender pornography features performers gay hentai who cross-dress for sexual gratification, either for themselves or for their partners. 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. The other person may do the same during or after. A related term used in the genre is the term cougar, which implies an older woman as predator. The existence of such content in commercially available pornography is widely considered an urban legend. The loose and direct camera work often includes tight shots of horny milfs the genitalia, unlike some traditional porn. These gay sex video actors often play the top roles but this is not always the case, such as with Kristen Bjorn and some Bel Ami models. In Japan, point of view pornography is referred to as hamedori . The term pearl necklace is used by some because the drops of semen deposited by the man resemble a necklace of translucent white pearls. Examples of mentally oriented practices are education games, during which the dominant requires certain forms of behavior from the submissive. Lying face down on a comfortable surface such as a mattress or pillow, the penis can be rubbed against it. The most common type of erotic spanking is administered on the bare buttocks, but can also be combined with bondage, in order to heighten sexual arousal and feelings of helplessness.
