Tone and pitch perception in Yoruba

One dichotic listening experiment studying hemispheric specialization for pitch in a linguistic context (Thai) (Van Lancker and Fromkin, 1973) found a right-ear advantage for words that are differentiated by tone only; in another study (Cantonese) (Benson, Smith, and Arreaga, 1973) no ear advantage was found for perception of tone in words. Both studies included contour tones, i.e., stimuli which involve pitch changes in time; however, it has been established that the left hemisphere is involved in temporal-order processing of auditory and visual stimuli (Cartoon and Nachson, 1971), and that subjects with left-hemisphere brain damage show impairment in processing temporally ordered auditory stimuli (Efron, 1963). Since the left hemisphere's sequence-processing role may be a factor in the processing of contour tones, a question remains regarding ear advantage in perception of purely level (i.e., noncontour) tones. Our study tests ear advantage in perception of level tones by speakers of Yoruba. Three sets of monosyllabic word pairs are presented dichotically: (1) pairs differing in tone only, (2) pairs differing in initial consonant only, and (3) a monosyllable presented on different musical pitches. Relative degree of hemispheric specialization is compared for each set.