Central auditory processing : IV. Ear dominance—Spatial and temporal complexity

Ear dominance for dichotically presented tones was measured in 63 right-handed subjects when the frequency difference (Δf) was small compared to the center frequency (f_c) and again when it was large. Although two-thirds of the population exhibited a left-ear dominance in both conditions, a shift toward right-ear dominance occurred when the Δf was increased. An additional study, employing the alternating tone illusion described by Deutsch, revealed the same general effect, i.e., a shift toward right-ear dominance with increasing values of Δf/f_c. The results of these experiments, coupled with a review of previously published data of other dichotic experiments, indicate that as the ratio of Δf/f_c increases, the subjective complexity of the sound image increases, and there is a progressive emergence of a “right-ear advantage” (or ear dominance). A tentative explanation relates these results to the effects of anatomical asymmetries of primary and auditory association cortex and the efferent temporal lobe enhancement mechanism described by R. Efron, P. H. Crandall, B. Koss, P. L. Divenyi, and E. W. Yund (Brain and Language, 1983, 19, 254–263.