Perception of emotional intonation by brain-damaged adults: the influence of task processing levels.

This research examined perception of moods from the tone-of-voice of semantically neutral phrases following unilateral cerebrovascular accident. It was hypothesized that right hemisphere damage (RHD) would impair even low-level discrimination and recognition of affective prosody, while left hemisphere damage (LHD) would affect performance only as associational-cognitive task demands increased. Thirty-three male subjects, 11 each in RHD, LHD, and normal groups, were given three tasks that varied in presumed amounts of processing undertaken for successful completion. Discrimination of prosodic patterns was expected to require the fewest cognitive operations. An intermediate task involved selecting from two possibilities the label that described moods conveyed prosodically. In the third task, prosodic mood selection was made from four choices, increasing the number of comparisons necessary for accurate judgment. As hypothesized, RHD subjects were inferior to normal subjects in all tasks. LHD subjects were equivalent to normal subjects for the first two tasks, but fell to the level of the RHD group for the third task. These results indicated that the right hemisphere in men was primarily involved in the reception and recognition of emotional prosodic stimuli. Increasing cognitive demands, however, brought about a shift in emphasis from the right hemisphere to both hemispheres. An implication of these findings concerns the need to examine performance levels that invoke changes from expected patterns of hemispheric specialization to advance our knowledge of functional asymmetries.