A precedence effect in the perception of inter-aural cross correlation.

Does the precedence effect, well known in the field of sound localization or lateralization, also apply to other percepts based on binaural processing? We have compared, with one and the same experimental paradigm, a manifestation of the traditional precedence effect in lateralization with a possible similar effect in the perception of diffuseness or compactness of a sound image. With dichotic headphone stimulation, lateralization was controlled by the inter-aural time delay (IATD), and diffuseness/compactness by the inter-aural cross correlation (IACC). The experimental paradigm rests on the principle of estimating the over-all sensation of a 20-ms noise burst, which was subdivided in two parts, with the relevant dichotic information (IATD or IACC) in the leading part being opposite to that in the trailing part. When each part is 10 ms, it is found that the overall sensation is slightly dominated by the information in the leading part, both for lateralization and for compactness/diffuseness. This dominance of the leading part can be compensated by a certain decrease of its duration and/or amplitude relative to that of the trailing part. It is found that this quantitative measure for the 'strength' of the precedence effect for the present stimulus is essentially the same for IATD and IACC, suggesting that the precedence effect does not apply exclusively to sound localization or lateralization, but to at least one other percept based on binaural processing as well, namely the processing of inter-aural cross correlation.