AN ERA'S CONVENTIONAL WISDOM has a remarkable ability to color perceptions, seducing people to linger over certain facts and to hurry past others. In the early 1960s, for instance, when the prevailing cultural belief was that nurture, not nature, was the prime shaper of human beings, one of us sat with colleagues behind a one-way mirror watching a mother with her autistic, 6-year-old son. When the clinical team tried to get the child to sit on his mother's lap, he stiffened and looked away, while his mother seemed only remotely interested in the whole experiment. Watching behind the mirror, the team was convinced that they were witnessing "icebox mothering," then presumed to be the cause of childhood autism and schizophrenia. Never mind that this particular mother had raised other perfectly healthy children and had already spent years in frustrating interaction with this heartbreakingly difficult child. The clinical team was looking for icebox mothering, and that's what they found. In the grips of the "radical environmentalism" of the day, many of us also subscribed to the view that the boom-and-bust cycles of manic-depression were outward signs of excessive achievement strivings presumably inculcated in children by overambitious parents. We scoffed at the few "genetic determinists" among us who suggested that bipolar disorder might prove to have neural and biochemical origins. Similarly, we were sure that male homosexuality was an arrested stage of psychosexual development caused by a dominant, overbearing mother and a weak, passive father. The idea that sexual orientation might be partly or wholly due to genetic variation struck us as laughably archaic. In the anything-is-possible '60s, the conventional wisdom conceded almost nothing to nature to the intractable biological powers that shape people's temperaments before they are born and continue to shape their personalities long after they leave the womb.
The Greek philosopher Heraclitus may have said "A man's character is his fate," Freud may have written "Biology is destiny" and grandmothers may have told many generations that "The leopard doesn't change his spots" and "The apple doesn't fall far from the tree." But in the '60s, even whispering such thoughts was radically out of favor. Lobotomies and electroshock had given biological psychiatry a bad name, and Hitler had done the same thing for genetics and eugenics. The human potential movement, the feminist movement and the War on Poverty were dawning, bringing with them a belief soon to become dogma in the plasticity and perfectibility of human nature.
The prevailing idea then was that human beings were blank slates, infinitely malleable by their environments and fully capable of reinventing themselves. We dismissed the notion that depression, shyness, phobias, aggressiveness, schizophrenia, impulsivity, criminality you name it were even partly caused by instincts, drives, inherited predispositions, defective neuro-transmitters or random genetic mutations. The root causes of such problems, most of us thought, lay in ambiguous family communication patterns, childhood mistreatment or other environmental influences. This view, in a slightly less extreme form, has continued to inform much American clinical work ever since. It suggests that if you rearrange family interactions or provide enough intensive psychotherapy, you can create radical personality change.
But for the three of us, as well as others, long-held beliefs in radical environmentalism especially in the importance of early family influence and the malleability of basic temperament have gradually been replaced by perspectives that give more weight to biological foundations. In the 1960s, lithium's miraculous success with manic-depression and Thorazine's mixed but helpful results with schizophrenics began the demolition process. More of the structure collapsed in the 1970s and 1980s, when large-scale research with adoptees and identical twins teased out the relative influences of nature and nurture. …