A sexual surrogate, sometimes called a surrogate partner, is a member of a sex therapy team consisting of client(s), supervising therapist, and surrogate. Some couples attend sexual surrogacy sessions together, while some people (either single or in a couple) attend them alone. The surrogate engages in education and often intimate physical contact and/or sexual activity with clients to achieve a therapeutic goal. Masters and Johnson introduced the practice in their textbook on Human Sexual Inadequacy, published in 1970.