The two hemispheres of the human brain differ in their function. For example, speech perception and production are in most individuals controlled by the left hemisphere. A traditionally, easy-to-use way of determining whether an individual processes speech in the left or the right hemisphere is the so-called dichotic-listening test. In this paradigm, participants are asked to listen to and repeat speech sounds which are presented via headphones. The sounds are presented in “stereo”, that is, one sound is presented to the left ear, while another one is presented simultaneously to the right ear. Participants with assumed left-hemispheric dominance report the right-ear stimulus with higher probability than the left-ear stimulus, and vice versa. However, there are substantial differences between individuals and from trial-to-trial.
In this review article, René Westerhausen (LCBC, University of Oslo) and Kristiina Kompus (University of Bergen) give an in-depth account of specific features of stimulus material and experimental set-up as well as the conditions of stimulus/response selection, which explain a significant proportion of these differences. In this, the present article provides a comprehensive overview of the factors that should be considered in order to achieve an unbiased and fair testing situation when applying dichotic listening for measuring speech laterality in research and clinical evaluation.