Dichotic listening indices of right hemisphere semantic processing.

A new dichotic listening technique, based on a psychophysical threshold procedure and providing ordinal scale measurement of lateral asymmetry, was used to investigate variation in the size of right-ear advantage for verbal vs manual response modalities across three semantic categories of stimuli in 60 right-handed males. For manual responders, abstract words elicited a significantly greater right-ear advantage than did concrete words, while emotional words elicited a non-significant left-ear advantage. Verbal responders showed no significant difference in the size of right-ear advantage across stimuli. The results suggest that both response modality and stimulus type are important variables for dichotic listening paradigms seeking evidence of right hemisphere contributions to semantic processing.