Individual differences in general intelligence and in 8 different special aptitudes or skills were hypothesized to be independent of family size and birth order indices. Evidence to the contrary, in the form of linear correlations, was predicted to be due to the confounding influence of socio-economic factors. Among the more familiar demographic indices, only sex was expected to be a source of variation in special aptitude--over and above general intelligence. Data for testing these hypotheses were obtained from the "Project Talent Data Bank." The hypotheses were generally supported. Intelligence and special ability were found to be independent of family size and birth order indices when socio-economic differences in intelligence were removed. No differences in special ability were associated with socio-economic status after differences due to general intelligence were removed. These findings discount the need for special educational programs which might be planned for later born children on the assumption that they are intellectually handicapped. The sex differences in ability may justify existing differences in vocational programs for boys and girls. But the actual reasons for these differences require further study. (Author)