But starting with The World Biggest Gangbang , starring Annabel Chong, the pornographic industry began producing a series of films ostensibly setting gangbang records for most consecutive sex acts by one person in a short period. Lesbianism has been a hentai porn theme in erotic art since at least the time of ancient Rome, and many regard depictions of lesbianism to be erotic. Such films continued to be produced but could only be distributed by underground lesbian milfs channels. Rough sex pornography is similar to pornography featuring sadomasochism, and typically features a Top who humiliates and/or degrades a Bottom while being physically violent towards them. This category also includes pornographic home movies. Greater economic and social freedom allowed them gradually to be able to determine how they could form relationships and families. Freud, however, considered such extensions of sexual interest to fall within the range of the normal, unless marked out by exclusivity . Others may also use vibrators and other sexual devices more commonly associated with female masturbation. Babysitter pornography features usually teenage girls being exploited and having taboo sex with older, male employers. Fistees who are more experienced may take two fists . Buck Angel is the best-known actor in this genre. In the 1970s, the hardcore pornography genre introduced the stereotypical cumshot scene as a central element of the hardcore film, in which the male actor ejaculates in a way ensuring maximum visibility of the act itself. Mammary intercourse is said by Alex Comfort to produce mutual orgasm in women with sensitive breasts , and it was one of the gay twinks nine substitute exercises for penetrative sexual activities, as detailed in the Paradis Charnels of 1903. Targets the male audience, but is much less popular than Yaoi. Bukkake pornography usually depicts numerous men having sex with one woman, with multiple, usually 10 or more, men ejaculating on the female face. Within a BDSM or D/s context, facesitting can be an especially intense form of erotic humiliation.