Bestiality is illegal in many countries. A pornographic work is characterized as hardcore if it has any hardcore content, no matter how small. The full-weight body-pressure, moisture, sex odors and darkness can be perceived as powerful sexual attractions or compulsions. Some aspects of the research community distinguish between female ejaculation and what is colloquially known as squirting or gushing. Many cultures describe pain as an aphrodisiac. Bear features a combination of middle-aged, hairy or overweight males. For much of the history of cinema and television, lesbianism was considered taboo, though since the 1960s it has increasingly become a genre in its own right. Today, pornographic films can be sold or rented on DVD, porno gay shown through Internet and special channels and pay-per-view on cable and satellite, and in adult theaters. Perhaps following the example set by gay pornography, they have become a popular subgenre within heterosexual pornography since the turn of the century, featuring both vaginal and anal ejaculations. Some may keep their hand stationary while pumping into it with pelvic thrusts in order to simulate the motions of sexual intercourse. For example, in Australia it is rated Refused Classification . If one person is penetrated by two objects, it is generically called double penetration . While anal sex is commonly associated with male homosexuality, research shows that not all gay males engage in anal sex and that it is not uncommon in heterosexual relationships. Group sex most commonly takes place in a private sex party or semi-public swinger gathering, but may also take place at massage parlors or brothels or, in some jurisdictions, at purpose-built locations such as sex clubs. 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. 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.