Spatial position versus ear of entry as determinant of the auditory laterality effects: a stereophonic test.

The study concerned discriminating between ear of entry and apparent spatial position as possible determinants of lateral asymmetries in the recall of simultaneous speech messages. Apparent localization to the left or right of the median plane was created either through a time difference (.7 msec), through intensity differences between presentations of the same verbal message at the two ears, or through dichotic presentations. Right-side advantage was observed with the three types of presentation (Experiments 1, 2, and 3). The finding of right-side advantage with stereophony based on a time difference only, in the absence of intensity difference, cannot be accounted for in terms of an ear advantage and shows that apparent spatial separation of the sources can by itself produce a laterality effect. Differences in the degree of lateral asymmetry between the various conditions were also observed. The findings of Experiments 4 and 5 suggest that these differences are better explained in terms of different impressions of localization of the sound sources than in terms of relative intensity at the "privileged" ear.