A type of art in which the artist uses his or her own body as the medium; it is closely related to Conceptual art and Performance art, and flourished mainly at the same time that these forms of expression were at their peak—the late 1960s and 1970s (there was something of a revival in the 1990s). Sometimes works of Body art are carried out in private and communicated by means of photographs or films; sometimes the execution of the ‘piece’ is public. The performance may be pre-choreographed or extemporaneous. Spectator participation is not usually invited. Body art is often playful in spirit, but several leading exponents have been concerned with self-inflicted pain or ritualistic acts of endurance. For example, in ‘Seedbed’ (1972) the American Body artist Vito Acconci (b 1940) spent several hours daily masturbating under a gallery-wide ramp while the sounds of his activity were relayed via loudspeakers to visitors overhead. The philosophy behind such works is obscure.