Cum swapping pornography involves performers trading semen between their mouths. Social attitudes towards the discussion and presentation of sexuality has become more tolerant and legal definitions of obscenity have become more limited, leading to an industry for the production and consumption of pornography in the latter half of the 20th century. Often a dominant woman, she may be called a Dom, Domme /ˈdɒm/, Femdomme, Domina, or Dominatrix, depending on context or personal preference. Gang bang pornography is a type hentai porn of pornography that depicts an individual engaging in physical sexual activity with multiple partners sequentially or at once. The nipples are erogenous zones, and vigorous stimulation of them during masturbation usually causes the penis to become erect more quickly than it would otherwise. As of 2010, they were reported to live together as a monogamous couple outside of their porn careers and want to continue working together for another 50 years. However the genre remains a very small proportion of the pornographic nude milfs DVD market; for example at porn retailer HotMovies. BDSM pornography depicts bondage and discipline, domination and submission, sadism and masochism. Exhibitionist pornography features performers, usually female exposing themselves in public and spans simple flashing to public sex. Failure to honor a safeword is considered serious misconduct and could even change the sexual consent situation into a crime, depending on the relevant law, since the bottom has explicitly revoked his or her consent to any actions that follow the use of the safeword . The interaction between tops and bottoms—where physical or mental control of the bottom is surrendered to the top—is sometimes known as power exchange, whether in the context of an encounter or a relationship. In a separate article analyzing 12 men who engaged in bestiality, an additional analysis of an 11-man subgroup revealed that 6 had engaged in coprophilic behavior, compared with only 1 in the matched control group gaysex consisting of 12 SM-oriented males who did not engage in bestiality.