Age differences in backward masking

The present study was designed to assess the effects of age on the time course of backward masking. In experiment 1, thresholds for detecting a 10- ms, 500-Hz sinusoidal signal were measured as a function of the temporal separation between the signal and a 50-ms broadband masker. Subjects were younger (18-24) and older (over age 65) adults with normal hearing (thresholds less than 20 dB HL) for frequencies of 4 kHz and below. Younger subjects exhibited less overall masking and steeper recovery functions than did the older adults. Masked thresholds for younger participants approached unmasked thresholds for signal-masker delays greater than 6-8 ms. In contrast, older adults exhibited significant masking even at the longest delay tested (20 ms). In experiment 2, signal duration was decreased to 5 ms for a separate group of younger adults. Although overall thresholds were elevated for the shorter signal duration, the slope of the backward masking recovery function was not different from that observed for younger adults in experiment 1. The results suggest that age, independent of hearing loss, affects the temporal course of backward masking.