Age-related changes in within- and between-channel gap detection using sinusoidal stimuli

Pure tone gap stimuli with identical (within-channel) or dissimilar (between-channel) marker frequencies of 1 and 2 kHz were presented to young and old listeners in a two-interval forced choice gap detection task. To estimate the influence of extraneous duration cues on gap detection, thresholds in the between-channel conditions were obtained for two different sets of reference stimuli: reference stimuli that were matched to the overall duration of the gap stimulus, i.e., two markers plus the gap, and reference stimuli that were fixed at the combined duration of the two markers excluding the gap. Results from within-channel conditions were consistent with previous studies, i.e., there were small but highly reliable age differences, smaller gap thresholds at longer marker durations, and an interaction between the two variables. In between-channel conditions, however, age differences were not as clear cut. Rather, the effect of age varied as a function of duration cue and was more pronounced when stimuli were matched for overall duration than when the duration of the reference tone was fixed.