Reading or viewing pornography, sexual fantasy or other erotic stimuli may lead to a desire for sexual release such as by masturbation. Both sexes sometimes apply lubricating substances to intensify sensation. Lying face down one may use the hands, one may straddle a pillow, the corner or edge of the bed, a partner leg or some scrunched-up clothing and hump the vulva and clitoris against gay boy porn it. Being forced to wear diapers as a form of humiliation is sometimes a behavior encountered in sexual masochism. It is geared towards heterosexual men, who most typically define a threesome as such. Contrary to the other two types, B/D does not define the Tops and Bottoms itself, and is used to describe the general activities with either partner being the receiver and the giver. Types of anal sex can also be a part of lesbian sexual practices. The Girls Gone Wild gay hentai series is one example. Lolita pornography caters to ephebophiles. These are often fake. The glans itself may widen and lengthen as the stimulation continues, becoming slightly darker in colour, while the gliding action of the foreskin reduces friction. The two sets of people involved often meet either randomly or arrange to meet up beforehand over the Internet. Solo pornography recognized with AVN Awards include the All Alone series and All Natural: Glamour Solos. Preggo pornography features pregnant performers and may include erotic lactation as a fetish. Breast fetishism is a paraphilic sexual interest focused on female breasts . Unlike the usual power neutral relationships and play styles commonly followed by couples, activities and relationships within a BDSM context are often characterized by the participants taking on complementary, but unequal roles; thus, the idea of informed consent of both the partners becomes essential. The term BDSM dates back to 1969; however, the origin of the term BDSM is unclear and is believed to have been formed either from joining the term B&D porn milf with S&M , or as a compound initialism from B&D, D&S , and S&M.