How to get a left-ear advantage: A technical review of assessing brain asymmetry with dichotic listening.

The dichotic-listening paradigm with verbal stimuli is a widely employed behavioral task for the assessment of hemispheric asymmetry for speech and language processing. Participants with assumed left-hemispheric dominance report the right-ear stimulus with higher probability than the left-ear stimulus. However, there is substantial between-subject and trial-to-trial variability observed in the paradigm, motivating scrutiny of the task set-up and theoretical models. Here, we give an in-depth discussion of specific features of stimulus material and experimental parameters, as well as the conditions of stimulus/response selection, which explain a significant proportion of intra- and inter-individual variability. Carefully considering these factors should be at the heart of any experimental planning when using the dichotic-listening paradigm to achieve an optimal testing situation for measuring laterality and avoid confounds in between-subject and between-group comparisons.