MENTAL AGES AND SOCIAL AGES OF NORMAL AND DEFECTIVE TWINS AND SIBLINGS.

The article discusses the nature-nurture problem by a study of the relative variables reflected in mental disabled twins and siblings. The method used in the research is a comparative study of the similarity in social competence within the twinned pairs and also a comparison of their mental levels, which information was available only for the mentally deficient group. The results show that there is a consistency in the differences in mental abilities and social functioning found within the identical twins, fraternal twins and sibling groups in both the normal and feebleminded experiments and variations of heredity and environment within the pairs.