The Masters and Johnson research team head by William H. Masters (1915-2001) and Virginia E. Johnson (born 1925) pioneered research into human sexuality from 1957 until the 1990s. The follow-up to this volume is
Human Sexual Inadequacy.
They wrote in the Preface to this 1966 book, "If problems in the complex field of human sexual behavior are to be attacked successfully, psychologic theory and sociologic concept must at times find support in physiologic fact. Without adequate support from basic sexual physiology, much of psychological theory will remain theory and much of sociological concept will remain concept... This text represents the first step, a faltering step at best, but at least a first step toward and open-door policy. The door of investigative objectivity must not be closed again." They acknowledge that "The concentration of study subjects from upper socioeconomic and intellectual strata provided by this major source of supply has not been offset by a statistically significant number of lower-range family units obtained from out-patient clinic sources." (Pg. 11)
They summarize: "A more concise picture of physiologic reaction to sexual stimuli may be presented by dividing the human male's and female's cycles of sexual response into four separate phases. Progressively, the four phases are: (1) the excitement phase; (2) the plateau phase; (3) the orgasmic phase; and (4) the resolution phase. This arbitrary four-part division of the sexual response cycle provides an effective framework for detailed description of physiologic variants in sexual reaction." (Pg. 4)
They observe, "The importance of development by marital units of specific coital techniques to facilitate clitoral stimulation has been emphasized repeatedly in the literature." (Pg. 59). They significantly note, "The human female frequently is not content with one orgasmic experience..." (Pg. 64) Later, they add, "the female is capable of maintaining an orgasmic experience for a relatively long period of time." (Pg. 131)
They note, "alteration in male responsive ability usually falls within one or more of six general categories: (1) monotony of a repetitious sexual relationship... (2) preoccupation with career or economic pursuits; (3) mental or physical fatigue; (4) overindulgence in food or drink; (5) physical or mental infirmities of either individual or his spouse; (6) fear of performance ..." (Pg. 260)
Masters and Johnson (who later married, but still later divorced) were the first truly "scientific" sex researchers, and their pathfinding work remains of interest.