Starting with erotic stories and woodblock prints from before the 20th century, Japanese pornography evolved into distinct subcategories with the media that in addition of hot gay sex pornographic videos and magazines featuring live actors, there is exist categories of pornographic manga , pornographic computer games , and pornographic anime . 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. Advocates of RACK argue that SSC can hamper discussion of risk because no activity is truly safe, and that discussion of even low-risk possibilities is necessary for truly informed consent. Particular areas and processes of the body that change during pregnancy may also hentai movies become the focus of psychological investment, but nudity porn milf or sexual activity is not always essential, and in some cases actual pregnancy is not necessary to invoke arousal. The range of its individual characteristics is thereby wide. Snowballing or snowdropping is the human sexual practice in which one person takes someone else semen into his or her mouth and then passes it to the mouth of the other, usually through kissing. Although there may be no connection between coprophilia and sadomasochism , the limited data on the former comes from studies of the latter. Solo performances in gay pornography have been described in 1985 as either or both active and/or passive , whereas female solo performances are said to be exclusively passive . When the interest in a particular subject is obsessive, the behavior may be described as stalking. Use of the agreed safeword is seen by some as an explicit withdrawal of consent. New York photographer Irving Klaw also published illustrated adventure/bondage serials by fetish artists Eric Stanton, Gene Bilbrew, Adolfo Ruiz and others. There is, however, no third party camera work involved. Voyeur pornography may also include shots of topless women on topless beaches who are unaware of the cameras but may legally be photographed due to the public setting.