Psychosomatic Medicine 22:251-258 (1960)
© 1960 American Psychosomatic Society

Homosexuality and Heterosexuality in Identical Twins

¹ New York State Psychiatric Institute and the Department of Psychiatry, College of Physicians and Surgeons, Columbia University New York, N. Y.

Two sets of identical twins, one male and the other female, have been studied in whom the development of the overt psychosexual role was divergent in the sense that one of each pair was heterosexual while the other was homosexual. In the male pair the roles were overtly determined to the extent of genital satisfaction; in the adolescent female pair the roles were determined but without as yet overt sexual intimacies.

The determining life experiences for the differentiation of the sexual role were found in the prenatal fantasies of the parents of one pair for a child different in sex from that of the twins at birth; and a slight but definite anatomical differentiation in the twins which determined for the mother a special attachment for one or the other child. There resulted early differentiation of the body ego for each of the individuals and later in life enhancement of the sexual role through the existence or deprivation of significant extrafamilial relations. Of significance also was the parental attitude toward the role of the individual child disclosed through the naming of the child.

Biologically appropriate sexual behavior was unrelated to the type or degree of psychopathology.

Homosexual seduction in itself was not found to determine homosexual behavior nor deter heterosexual behavior.

Neurological and various biochemical examinations failed to reveal differences between these identical twin pairs divergent for homosexuality and heterosexuality.