The psychoanalyst Sigmund Freud distinguished female orgasms as clitoral in the young and immature, and vaginal in those with a healthy sexual response. Unsurprisingly, given that experts are yet to come to a consensus regarding the definition of an orgasm, there are multiple different forms of categorization for orgasms. It is also important to note that not all sexual activity is preceded by desire. Kaplan’s model differs from most other sexual response models as it includes desire – most models tend to avoid including non-genital changes. The following models are patterns that have been found to occur in all forms of sexual response and are not limited solely to penile-vaginal intercourse. Although the orgasm process can differ greatly between individuals, several basic physiological changes have been identified that tend to occur in the majority of incidences. Sex researchers have defined orgasms within staged models of sexual response. This research led to the establishment of sexology as a scientific discipline and is still an important part of today’s theories on orgasms. Masters and Virginia Johnson in their work, Human Sexual Response (1986) – a real-time observational study of the physiological effects of various sexual acts. The spirit of this work was taken forward by William H. Alfred Kinsey’s Sexual Behavior in the Human Male(1948) and Sexual Behavior in the Human Female (1953) sought to build “an objectively determined body of fact and sex,” through the use of in-depth interviews, challenging currently held views about sex.