Hemispheric specialization in processing intonation contours

Hemispheric specialization in processing linguistic and non-linguistic intonation contours during sentence processing was examined in four experiments using subjects with unilateral left (LHD) or right hemisphere damage (RHD). When subjects were asked to identify intonation contours as questions or statements in semantically neutral sentences, the LHD group demonstrated a significantly poorer performance than the control group. No significant differences were found between the RHD and control groups. When subjects were asked to identify syntactically ambiguous sentences through the perception of intonation cues located at syntactic boundaries the same pattern of results emerged. In discriminating between the aforementioned segmentally identical sentences, no significant differences were found between groups. However, when the segmental information was degraded and subjects were asked to discriminate between isolated prosodic structures, the RHD group demonstrated a significantly poorer performance than the control group. No significant differences were found between LHD and control groups. This inverse pattern of results suggests a left hemisphere dominance in processing intonation contours that have a linguistic function. When the linguistic significance was reduced, the right hemisphere was dominant. Results are discussed in relation to predictions made by two different hypotheses regarding hemispheric specialization in processing prosody.