| Abstract: | The statistical analysis of difference scores (contrasts) is a fundamental problem in all learning, feeding, and training experiments and tests, and in longitudinal studies of growth and development. Outgoing from the analogy between the mathematical models of classical psychological test theory and quantitative genetics, as well as between the parameters reliability and heritability of these models, the present paper derives the formulas of the heritability of difference scores in general cases where it is not assumed that environmental deviations on distinct tests and measurements are uncorrelated. Contrary to the assertion, made by FELDMAN and LEWONTIN , heritabilities in the broad sense can be used as ideal weighting factors in long-range personnel index selection. Longitudinal studies of twins and the cotwin method are powerful experimental designs to estimate heritabilities of differences. |
