"While at Washington University, Johnson met research partner and future husband William Masters. The two developed the first tools for measuring sexual arousal in humans. ... Johnson and Masters identified the four stages of sexual response: the excitement phase, plateau phase, orgasmic phase, and resolution phase. The stages became known as the human sexual response cycle."
Masters and Johnson married in 1971. "She remained his wife and collaborator for 22 years," The New York Times has written, "the union finally ending because, she said, she wanted to spend more time with family and friends and he remained deeply absorbed in his work." Masters died in 2001.
The couple, the Times added, "revolutionized the way sex is studied, taught and enjoyed in America." They devoted "more than half a century to observing, measuring, pondering and demystifying the mechanics of sexual intercourse and determining how to make the sexual experience better for couples who found its pleasures elusive if not unattainable."
The Post-Dispatch notes that Masters and Johnson "were based in St. Louis and recruited members of the community for their work. The co-workers had an affair, then married (and later divorced). They started their work at Washington University and later founded their own nonprofit entity."