Dichotic Listening to Melodic Patterns and Its Relationship to Hemispheric Specialization of Function

Ear advantages in dichotic listening are generally held to reflect greater involvement of the hemisphere contralateral to the preferred ear. Rationales for this view rely on the assumption that, when information arriving at the two ears is treated as a single complex signal, an advantage to a component of this signal based on ear of input will not interact with an advantage based on some other attribute, such as frequency. This assumption is shown, for the case of dichotically presented melodies, to be unjustified. Dichotic tone pairs that are presented in a sequential context are more accurately perceived and localized when the higher tone is to the right and the lower to the left, than when the higher tone is to the left and the lower to the right. This anisotropy can, in principle, give rise to patterns of ear advantage which may tend in either direction, depending on factors such as type of material presented, level of difficulty, task requirement, and category of listener. Since its basis is unknown, ear advantages resulting from this anisotropy cannot be assumed to reflect greater involvement of either hemisphere in processing the information.