Effects of aging on the precedence effect in sound localization

The precedence effect in sound localization can be evoked by presenting identical sounds (e.g., clicks) from pairs of loudspeakers placed on opposite sides of a subject's head. With appropriate inter-loudspeaker delays, normal subjects perceive a fused image originating from the side of the leading loudspeaker. Separate tests at loudspeaker delays ranging from 0 to 8 ms were presented to groups of young and elderly subjects. At 0 ms delay, young subjects perceived the fused image to be located halfway between the loudspeakers; at progressively longer delays, the image was perceived closer to the leading loudspeaker. Significant numbers of elderly subjects exhibited discrimination difficulties with delays below 0.7 ms.