In the 1920s, Havelock Ellis reported that turn-of-the-century seamstresses using treadle-operated sewing machines could achieve orgasm by sitting near the edge of their chairs. The speed of the hand motion will vary from person to person, although it is not uncommon for the speed to increase as ejaculation nears and for it to decrease during the ejaculation itself. Ethnic pornography is a genre of pornography that features performers of specific ethnic groups, or depictions of interracial sexual activity. Common phrases used to refer to these individuals are chicks with dicks, trannies, or shemales, although these are generally considered pejorative slurs among transwomen. Com, there are only 655 bisexual titles out of a catalogue of more than 90,000 films. This is sometimes the case for punishment scenes between master/slave couples or for some extreme or edgeplay scenes which may include abductions, rape play, or interrogation. Contact mutual masturbation One person touching another person to masturbate. This practice has a distinct effect of immobilization and pain. It is distinguished from these concepts in that the cuckold thrill in their partner acts is specifically masochistic; gayporn as such it is considered a category of BDSM fetish. Twink pornography features younger performers, and usually features young men under 30 who identify as gay or bisexual. The principal characteristic of voyeurism is that the voyeur does not normally interact directly with the subject of his/her interest, who is often unaware of being observed. Masturbation involves touching, pressing, rubbing or massaging a person genital area, either with the fingers or against an object such as a pillow; inserting fingers or an object into the anus ; and stimulating the penis or vulva with an electric vibrator, which may also be inserted into the vagina or anus. In these cases, the appearance of an enlarged abdomen caused by obesity or overeating may be sufficient, or simply the suggestion of a protruding navel.