In an effort to provide a unifying framework for understanding monaural and binaural processing of intensity differences, an experiment was performed to assess whether temporal weighting functions estimated in two-interval monaural intensity-discrimination tasks could account for data in single-interval interaural intensity-discrimination tasks. In both tasks, stimuli consisted of a 50-ms burst of noise with a 5-ms probe segment at temporal positions ranging between the onset and offset of the overall stimulus. During the probe segment, one monaural interval or binaural channel of each trial contained an intensity increment and the other contained a decrement. Listeners were instructed to choose the interval/channel containing the increment. The pattern of monaural thresholds was roughly symmetrical (an inverted U) across temporal position of the probe but interaural thresholds were substantially higher for a brief time interval following stimulus onset. A two-sided exponential temporal window fit to the monaural data accounted for the interaural data well when combined with a post-onset-weighting function that described greatest weighting of binaural information at stimulus onset. A second experiment showed that the specific procedure used in measuring fringed interaural-intensity-difference- discrimination thresholds affects thresholds as a function of fringe duration and influences the form of the best-fitting post-onset-weighting function.
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The authors would like to thank Dr. Armin Kohlrausch, Dr. Pat Zurek, and two anonymous reviewers who provided helpful comments and suggestions for improving this paper. This work was supported by Research Grant No. R01 DC 00683 and Research Grant No. R03 DC 05343, both from the National Institute on Deafness and Communication Disorders, National Institutes of Health. 1