A theoretical note on sex linkage and race differences in spatial visualization ability.

Evidence on the poorer spatial visualization ability in various Negro populations compared to the white populations and on the direction and magnitude of sex difference in spatial ability relative to other abilities suggests the genetic hypothesis that spatial ability is enhanced by a sex-linked recessive gene and that, since the 20-30 percent admixture of Caucasian genes in American Negroes came mostly from male white ancestors, relatively fewer X-linked than autosomal Caucasian genes were transmitted to the American Negro gene pool. The genetic model as explicitly formulated indicates the kinds of data which could substantiate or disporve the theory, but which do not now exist.