Frequencies of three cerebral dominance genotypes who show right or left ear superiority on a verbal dichotic listening test and left or right field superiority on a tachistoscopic lateral field test of perceptual dominance are deduced. A hypothesis is offered relating direction of cerebral dominance, as defined by genotype, to degree of lateral specialization and perceptual ability, and a theoretical distribution of subjects according to spatial-perceptual ability and lateralization is derived. This distribution corresponds almost exactly with empirical data, thus confirming the proposed correlation between lateralization and spatial-perceptual capacity.