To bring scientific opinion on homosexuality up to date, attention must be given to four further attacks upon the problem. Most closely in line with early search for physical causation are accumulations of exact somatic measurements by such different agents as the so-called Harvard group in their _Explorations in Personality—a clinical ... study of fifty men of college age_ (only a partial publication of their findings), and G. W. Henry in his _Sex Variants_. Neither of these studies has, so far as published material indicates, established significant correlations between homosexuality and any somatic factor or group of factors measured. A statistical study limited to genetics was made in Germany during World War II by Theodor Lang.[3] On the ground that the offspring of a large group of parents should by the law of probability be equally divided between the two sexes, he made a statistical count of the siblings of several thousand homosexual men. He found a greater proportion of males among these than among siblings of a control group of heterosexuals. From this he argued that the homosexuals, though somatically male, possessed more than the average number of female genes, their brothers having in the aggregate more of the male determinants. Like all such studies this has been attacked on the grounds of its statistical soundness, but it has not been discredited. More conclusive in the same field is J. F. Kallman’s study of twins, _Heredity in Health and Mental Disorder_ (1953). Dr. Kallman compared, among other things, the incidence of homosexuality in identical and non-identical twins. Identical twins showed an enormously larger percent of similar sexual behavior than the latter, and his evidence is conclusive that “a genetically oriented ‘imbalance’ theory ... can no longer be regarded as an implausible explanation for certain groups of ... homosexuals.”[4] In the psychoanalytic field such dissenters from the so-called pan-sexualism of Freud as Jung, Adler, Horney and others have assembled evidence that sex is not always the prime cause of neurosis. Freud found it to be so, they say, because in his day social taboo made it the most common cause of insupportable tension. Now that sexual standards are less rigid (thanks in part to Freud’s work), other factors such as the thwarting of the ego or long-continued insecurity appear of almost equal importance. To account for the homosexual, these later psychoanalysts suggest such causal factors as early social humiliation resulting in withdrawal from heterosexual competition, acute anxiety with regard to childbearing, or reluctance to assume responsibility for a family. Still regarding homosexuality as a neurosis, that is, an abnormal way of escaping an untenable situation, they leave unanswered the question as to what predisposes an individual to the choice of this particular solution of his difficulties.[5]