Internal ejaculation shots are a comparatively recent development in pornography; they are not found in early pornographic films. Sexologist Alfred Kind suggested that the buttocks is the primary sexual presentation site in primates. In more vigorous forms of fisting, such as punching or punchfisting, a fully clenched fist may be inserted and withdrawn slowly. Softcore gay pornography also exists; it at one time constituted the genre, and may be produced as beefcake pornography for heterosexual female and homosexual male consumption. Participants who exert sexual control over their partners are known as dominants or tops while participants who take the passive, receiving, or obedient role are known as submissives or bottoms. Some may keep their hand stationary while pumping into it with pelvic thrusts in order to simulate the motions of sexual intercourse. Transsexual pornography is a genre of pornography. New York photographer Irving Klaw also published illustrated adventure/bondage serials by fetish artists Eric Stanton, Gene Bilbrew, Adolfo Ruiz and others. Hardcore pornography is pornography that depicts penetration or extreme fetish acts, or both. It is sometimes combined with BDSM features. Other objects such as ball point pens and thermometers are sometimes used, although this practice can lead to injury and/or infection. Target audience are teenage / young adult women. Spanking can be administered in a number of spanking positions. On May 27, 2010 the television program The Doctors discussed the topic with dozens of teens, parents, and professionals. Comic books often featured characters being tied up and tying others up, particularly in damsel in distress plots. Use of the agreed safeword is seen by some porno gay as an explicit withdrawal of consent. Foot fetishism has been defined as a pronounced sexual interest in the feet or footwear. Some men also enjoy anal stimulation, with fingers or otherwise, without any prostate stimulation. John Stagliano is considered to have started the gonzo pornography genre with his Buttman series of films.