Particular areas and processes of the body that change during pregnancy may also become the focus videos porno gay of psychological investment, but nudity or sexual activity is not always essential, and in some cases actual pregnancy is not necessary to invoke arousal. Breeding is sometimes followed by felching, which involves sucking the semen from the partner anus. In some creampie films, both gay and straight, intercourse and internal ejaculation are followed by performers licking up the semen that has dripped from their bodies. This type of pornography is almost exclusively hentai, as true hermaphroditic humans are not fertile and are not usually found in nature. Whether or not licking and fondling is considered tea bagging was once debated on the Howard Stern Show. The term bondage describes the practice of Physical restraining. Diaper fetishism, nappy fetishism or diaperism, is a sexual fetish in which a person feels a desire to wear or use diapers. Some pornographic films use an artificial semen substitute to simulate or enhance creampie shots. Some aspects of the research community distinguish between female ejaculation and what is colloquially known as squirting or gushing. Evolutionary psychologists suggest that rounded buttocks may have evolved to be desirable 3d hentai trait because they provide a visual indication of the woman youth and fertility. Group sex pornography features at least two men and two women , usually more, who all perform sex acts on each other. Content featuring male bisexuality has been a growing trend since the advent of internet pornography. In humans, females generally have more round and voluptuous buttocks, caused by estrogen that encourages the body to store fat in the buttocks, hips, and thighs. The term is typically used by the cinematographer within the narrative framework of a pornographic film, and since the 1970s has become a leitmotif of the hardcore genre. Internationally, hentai is a catch-all mature milfs term to describe a genre of anime and manga pornography.