Reliability of laterality effects in a dichotic listening task with words and syllables

Large and reliable laterality effects have been found using a dichotic target detection task in a recent experiment using word stimuli pronounced with an emotional component. The present study tested the hypothesis that the magnitude and reliability of the laterality effects would increase with the removal of the emotional component and variations in word frequency. Thirty-two participants completed both a dichotic syllable detection task and a dichotic word detection task. In both tasks, stimuli were pronounced in a neutral tone of voice. Each task was completed twice to allow the estimation of test-retest reliability. Results failed to confirm the hypothesis since they were generally similar to those obtained in the previous study. A significant right ear advantage (REA) was found only with the word task. Although no ear advantage was found for the syllable task, somewhat better reliability was demonstrated compared to that obtained with words. The present findings suggest that including an emotional component does not reduce the reliability or magnitude of auditory laterality effects. In fact, the emotional component may have forced participants to focus on the language aspects of the stimuli. This might partly account for the reduced reliability in words and the absence of REA in syllables. Motivational factors inherent to the within-subject design used here are also discussed.