Johnson, who grew up in rural Missouri near the small town of Golden City, was a twice-divorced mother in her 30s when she went job-hunting at Washington University in St. Louis in the late 1950s. She was trying to support her young family while she pursued a college degree.
She soon became an assistant to obstetrician-gynecologist William Masters, and later his lover and co-collaborator on a large-scale human sexuality experiments.
Johnson recruited graduate students, nurses, faculty wives and other participants for what was described as the "biggest sex experiment in U.S. history." The after-hours research, first on the medical school campus at Washington University and later at a nearby building, shattered basic perceptions about female sexuality, including Freud's concept that vaginal -- rather than clitoral -- orgasm was the more mature sexual response for women.
She took the case studies -- and asked the uncomfortable questions.
Hundreds of couples, not all of them married, would participate in the observed research, later discussed in their 1966 book, "Human Sexual Response." That book and their second, 1970's "Human Sexual Inadequacy," were both best-sellers.
For the next 20 years, Masters and Johnson were celebrities, the topic of late-night talk show hosts and on the cover of news magazines.
"The family feeling was they changed the study of sex with the landmark publishing of their books," Scott Johnson said.
Her attorney, Dave Harlan, described Johnson as "strong willed, extremely intelligent, extremely independent."
Masters and Johnson married in 1971 and divorced after 20 years. The Masters and Johnson Institute in St. Louis closed in 1994. Masters died in 2001.
A private funeral is planned.
Copyright 2013 The Associated Press.