Cultural history of the buttocks desirability of buttocks: Since the early 2000s, songs about the female buttocks have proliferated, especially in the hip-hop, reggae/dancehall, and R&B genres. Buttocks are often emphasized in pornography. Patricia Hill Collins, an African-American post-modern feminist writer, theorizes that this is derived from a stereotype that black women are promiscuous, and their buttocks are objectified by pornography as a result. A buttocks fetish or buttocks partialism refers to a condition wherein the buttocks becomes a primary focus of sexual attention. It may be associated with coprophilia, panty fetishism, eproctophilia, and sadomasochistic corporal punishment involving the buttocks. "Pygophilia" refers to sexual arousal
Sexual arousal rats in the similar manner. Whether the regularity observed in frogs is applicable to humans remains unknown. Unambiguous experimental evidence for the existence of the Tarkhanov regularity in human sexual behaviour has never been obtained. Another explanation of sexual arousal is offered by the approach which Kazimierz Imieliński calls the "psychohydraulic model of sexuality." This point of view likens human sexuality to a steam boiler, with biological processes or internal irritants creating sexual tension. If the level of this tension reaches threshold, sexual arousal occurs as the expression of necessity to let off steam. Gary F. Kelly (Clarkson University) describes