12 PSYCHOTHERAPY: SCIENTIFIC AND RELIGIOUS chap.
present-day observer. Researchers who put their faith in family histories seem to have utterly ignored the pertinent fact that children of the Kallikak family were also reared in Kallikak environments. The observed results may be as much due to the social surroundings and to the cultural handicaps as to defective genes.
Whether or not personality disorders can be inherited is still more problematical, despite a vast amount of data made available by research. Perhaps in time the study of identical twins may lead to more precise knowledge of hereditary factors, although it is evident that such twins are almost always exposed to the same environmental influences.192 The psychoses of identical twins often have the same characteristics and are manifest at the same period in life, but this is by no means always true.83
Reinhardtl89 examines the evidence from twin studies for the inheritance of temperamental traits, with especial reference to the graphological analyses by Saudek and Seeman. Such studies have revealed marked similarities in personality traits among identical twins ; but the author shows that these might be explained by the peculiar social relationship of the pairs to their environment. Indeed, the very traits which have been found common to a given pair are those that might have resulted from their close community of feeling, and their united reaction to environmental influences.
Statistical data have been the basis of various studies on the relation of heredity to personality disorders, but these data include official diagnosis made in different hospitals or communities and are therefore not strictly comparable. In arriving at these diagnoses the factor of environment has often been neglected and yet from them some valuable conclusions may be drawn. Rudin,198 for example, has found that, if one or both