Buttocks are sometimes emphasized in pornography, where they are often referred to as booty. Top and dominant are widely recognized for those partner in the relationship or activity who are, respectively, the physically active or controlling participants. Being forced to wear diapers as a form of humiliation is sometimes a behavior encountered in sexual masochism. New York photographer Irving Klaw also published illustrated adventure/bondage serials by fetish artists Eric Stanton, hentai porn Gene Bilbrew, Adolfo Ruiz and others. 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 gay twinks objectified by porn as a result. Sadism describes sexual pleasure derived by inflicting pain, degradation, humiliation on another person or causing another person to suffer. Some people get sexual pleasure by inserting objects, such as urethral sounds, into the urethra , a practice known as naked milf urethral play or sounding. The term has also applied to other professions and even companies trying to appeal to a gay demographic. Exhibitionism: Becoming noticeably desperate or wetting oneself with the express purpose of being seen by strangers. Some men enjoy masturbating during pegging. Reality and voyeur pornography, animated videos, and legally prohibited acts also influence the classification of pornography. The purpose of this kind of agreement is primarily to encourage discussion and negotiation in advance, and then to document that understanding for the benefit of all parties. Instead, all five fingers are kept straight and held as close together as possible , then slowly inserted into a well lubricated vagina or rectum. Shotacon : Similar to Lolicon, this genre involves prepubescent or under-aged boys between the ages 6–12. Cartoon pornography includes, but is not limited to, hentai and parody renditions of famous cartoons and comics. A bisexual threesome may involve a man having sex with a man and a woman, the woman having sex with a man and a woman, or all three having sex with each other.