Bartholomeus (1974)
BARTHOLOMEUS, Bonnie. “Effects of Task Requirements on Ear Superiority for Sung Speech.” Cortex 10/3 (1974): 215-223.
Opens with a review of the pre-existing literature regarding laterality effects in audition during dichotic listening experiments. Notes that none of the previous studies had sufficiently tested whether these effects were entirely due to stimulus variables (i.e. acoustic features) or possibly influenced or determined by task requirements. Bartholomeus presents the view that speech processing involves two stages: auditory and phonetic, citing earlier work by Shankweiler and Pisoni (1972). She proposes two alternate hypotheses: (1) the presence of phonetically-encoded acoustic input is sufficient to cause right-ear (left hemisphere) effects; (2) task requirements will influence these laterality effects, such that only a phonetic discrimination task will cause right-ear superiority. In the current experiment, a dichotic listening paradigm was used. Three task conditions were set, each presented on a different day, but with the same subjects and the same stimuli in all cases. In this way, it was possible to directly test the question of task-influenced changes in laterality. The stimuli consisted of
pairs of melodies sung to different sequences of letters by different singers. (217)
The three tasks, performed on different days, required identification of singer, letter, or melody. The results were somewhat equivocal (in part because laterality effects were mostly nonsignificant), but weakly supported the second hypothesis that task influenced, in that
a trend towards right-ear superiority in perception of encoded acoustical information was observed only on the task which clearly demanded accurate phoneme recognition (letter sequence task). (221)
This study succeeds more in pointing up flaws in earlier experimental designs, and suggesting areas for future research, than in establishing a superior methodological paradigm.
