The relative influences of genetic and environmental factors in the development of human behavior have been intensely debated throughout the history of psychology. Theories of personality development have ranged from genetic determinism to extreme environmentalism, until environmentalism that attributes all human behaviors to an environment (“we are what we learn”) captivated developmental psychology in the 1950s. The more balanced view emphasizing interactions between genetic and environmental factors came to psychiatry in the 1960s and 1970s, but was slower to come to the field of personality. In the 1970s, there was still a debate about whether personality exists at all and whether behavior is determined by the environment only. A change towards an acceptance of genetic factors in personality development has been so rapid, that it is easily forgotten how “environmentalistic” the psychological explanations have been. Even in the 1960s, the major explanation for all personality disorders, including autism and schizophrenia, was inappropriate or abnormal parenting.