A related term used in the genre is the term cougar, which implies an older woman as predator. Interactive pornography, available in CD-ROM and DVD format, allows the viewer to select the particular acts performed at any one time, sometimes with the camera providing a first person view. What seems clear from the historical record is that much of the lesbian material in pornographic texts was intended for a male readership. Evolutionary psychologists suggest that rounded buttocks may have evolved to be desirable trait because they provide a visual indication of the woman youth and fertility. Transsexual porn star Wendy Williams has stated that transsexual Porn is classified as Straight Specialty. Other objects such as ball point pens and thermometers are sometimes used, although this practice can lead to injury and/or infection. Diaper fetishism, nappy fetishism or big tit milf diaperism, is a sexual fetish in which a person feels a desire to wear or use diapers. In Japanese, this natural-fibre rope is known as asanawa; the Japanese vocabulary does not make a distinction between hemp and jute. Bondage pornography specializes in the depiction of sexual bondage or BDSM activities as photographs, stories, movies, or drawings. Pornography may fall into more than one genre. Both forms of pornography generally contains nudity. Snowballing or snowdropping is the human sexual practice in which one person takes someone gay bear porn else semen into his or her mouth and then passes it to the mouth of the other, usually through kissing. Sometimes one or more fingers may be inserted into the anime hentai vagina to stroke its frontal wall where the G-spot may be located. If one person is penetrated by two objects, it is generically called double penetration . Sub-genres can also be classified into the characteristics of the performers or the type of sexual activity on which it concentrates, and not necessarily on the market to which each sub-genre appeals. Sexual relations between women have been illustrated as well as narrated, but much of the written material from the early modern period has been destroyed.