Major Gene Locus of Spearman's General Factor of Intelligence

Abstract

The reigning biometrical paradigm asserts that continuous variation implies the determination of intelligence by many genes with small effects. However, if an appreciable amount of the variability of a continuous trait is due to Mendelian segregation at a single locus, we may speak of the major locus for that trait. In such a case the distributions between the genotypic classes show considerable overlap, caused by error of measurement and environmental influences. As confirmed by Mendelian analysis, Spearman's general factor is the result of genotypes with discrete true scores of central processing time, the heterozygotes being exactly in the mean of the differences of the means of homozygotes.