The precedence effect: revisited.

The precedence effect, as investigated by Wallach et al. [Am. J. Psychol. 62, 324-336 (1949)] was studied in three experiments. Experiment I was a replication of the original work of Wallach et al. Although the first click pair appears to dominate the perception of the position of the lateral image, the effect of the first click pair does not appear to "offset" or "cancel" the effect of the second click pair in terms of producing a lateral image at midline. The data are consistent with Zurek's [J. Acoust. Soc. Am. 67, 952-964 (1980)] proposal that the binaural system is less sensitive to the interaural temporal difference of the second click pair. Experiment II indicated that the effect of the first click pair on lateral judgments still dominates that of the second click pair when the images are judged to be off midline. In all of these studies, the variability of the data is quite high. Experiment III showed that the first click pair also led to a larger change in masked thresholds (masking-level differences, MLDs) than does the second click pair. These data reconfirm the use of two-click stimuli for demonstrations of the precedence effect and they describe some of the limitations of the procedure and the generalities of the effect.