1953: Kinsey reports 39 per cent of women usually achieve orgasm.
1966: Masters & Johnson declare that sex research is ethically acceptable if the experimenter does not become erotically involved.
1968: Endurance tests on athletes show that sex before a match is not liable to harm performance.
1969: Invention of penile tumescence gauge to collect data.
1970: Invention of vaginal photoplethysmograph to measure female arousal.
1976: A survey finds 16 per cent of US medical students believe that masturbation is a cause of emotional and mental illess. And that 97 per cent of males and 78 per cent of females masturbate.
1979: A survey of rubber fetishists finds they are not more neurotic than average. But they are more prudish.
1980: A survey among US college students suggests that 51 per cent of males are performing oral sex on 31 per cent of females, and 31 per cent of females are performing on 58 per cent of males.
1991: A survey of US women reveals that those who do not shave their legs or armpits are more likely to be feminists or lesbian.
1992: Masters & Johnson divorce.