Final answer:
Masters and Johnson's research was pivotal in understanding the human sexual response cycle using direct observations and physiological measurements. Their work was critiqued but also greatly influenced the field of sexology.
Step-by-step explanation:
The truth about Masters and Johnson's research is that they made significant contributions to the understanding of the human sexual response cycle and employed direct observation as well as physiological measurements in their studies. Although their work concentrated on biological aspects rather than solely on psychological aspects, their pioneering approach and findings were both critiqued and highly influential in the field of sexology. In their landmark study, they observed nearly 700 participants engaging in sexual activities, collecting data that included parameters such as blood pressure, respiration rate, vaginal lubrication, and penile tumescence. This led to their development of the sexual response cycle, which has been an important framework in sexological research.