Final answer:
William Masters and Virginia Johnson are the researchers who identified the human sexual response cycle, dividing it into the phases of excitement, plateau, orgasm, and resolution.
Step-by-step explanation:
The researchers who conducted the studies that identified the human sexual response cycle were William Masters and Virginia Johnson. Their pioneering work led to the division of the sexual response into four phases: excitement, plateau, orgasm, and resolution. They observed a variety of sexual behaviors and physiological responses, collecting data that was influential in the field of sex research.
Masters and Johnson's observations of nearly 700 individuals participating in sexual activities allowed them to record changes in blood pressure, respiration rates, and indications of sexual arousal such as vaginal lubrication and penile tumescence. Their work resulted in a comprehensive understanding of sexual physiology and challenged many pre-existing notions about sex. Although their findings have been subject to criticisms and evolving insights, the importance of their contributions to the field remains significant.