in the 1940s and early 1950s all over the western world—the "Baby Boom Generation"—many of whom would grow up in relatively prosperous and safe conditions, within a middle class on the rise and with better access to education and entertainment than ever before. By their demographic weight and their social and educational background, they came to trigger a shift in society towards more permissive and informalized attitudes. The discovery of penicillin led to significant reductions in syphilis mortality, which, in turn, spurred an increase in non-traditional sex during the mid to late 1950s. There was an increase in sexual encounters between unmarried adults. Divorce rates were dramatically increasing and marriage rates were significantly decreasing in this time period. The number of unmarried Americans aged twenty to twenty-four more than doubled from 4.3 million in 1960 to 9.7 million in 1976. Men and women sought to reshape marriage by instilling new institutions of open marriage, mate swapping, swinging, and communal sex. Academic influences The Freudian school Sigmund Freud of Vienna believed human behavior was motivated by unconscious drives, primarily by the libido or "Sexual Energy". Freud proposed to study how these unconscious drives were repressed and found expression through other cultural outlets. He called this therapy "psychoanalysis". While Freud's ideas were sometimes ignored or provoked resistance within Viennese society, his ideas soon entered the discussions and working methods of anthropologists, artists and writers all over Europe, and from the 1920s in the United States. His conception of a primary sexual drive that would not be ultimately curbed by law, education or standards of decorum spelled a serious challenge to Victorian prudishness, and his theory of psychosexual development proposed a model for the development of sexual orientations and desires; children emerged from the Oedipus complex, a sexual desire towards their parent of the opposite sex. The idea of children having their parents as their early sexual targets were particularly shocking to Victorian and early 20th-century society. According to Freud's theory, in the earliest stage of a child's psychosexual development, the oral stage, the mother's breast became the formative source of all later erotic sensation. Much of his research remains widely contested by professionals in the field, though it has spurred critical developments in the humanities. Anarchist and Marxist Freud scholars Otto Gross and Wilhelm Reich (who famously coined the phrase "Sexual Revolution") developed a sociology of sex in the 1910s to 1930s