Age-related differences in gap detection: effects of task difficulty and cognitive ability

Abstract

Differences in gap detection for younger and older adults have been shown to vary with the complexity of the task or stimuli, but the factors that contribute to these differences remain unknown. To address this question, we examined the extent to which age-related differences in processing speed and workload predicted age-related differences in gap detection. Gap detection thresholds were measured for 10 younger and 11 older adults in two conditions that varied in task complexity but used identical stimuli: (1) gap location fixed at the beginning, middle, or end of a noise burst and (2) gap location varied randomly from trial to trial from the beginning, middle, or end of the noise. We hypothesized that gap location uncertainty would place increased demands on cognitive and attentional resources and result in significantly higher gap detection thresholds for older but not younger adults. Overall, gap detection thresholds were lower for the middle location as compared to beginning and end locations and were lower for the fixed than the random condition. In general, larger age-related differences in gap detection were observed for more challenging conditions. That is, gap detection thresholds for older adults were significantly larger for the random condition than for the fixed condition when the gap was at the beginning and end locations but not the middle. In contrast, gap detection thresholds for younger adults were not significantly different for the random and fixed condition at any location. Subjective ratings of workload indicated that older adults found the gap detection task more mentally demanding than younger adults. Consistent with these findings, results of the Purdue Pegboard and Connections tests revealed age-related slowing of processing speed. Moreover, age group differences in workload and processing speed predicted gap detection in younger and older adults when gap location varied from trial to trial; these associations were not observed when gap location remained constant across trials. Taken together, these results suggest that age-related differences in complex measures of auditory temporal processing may be explained, in part, by age-related deficits in processing speed and attention.

Figure 1

Mean pure-tone thresholds (dB HL) (±1 SEM) for the right ears (test ears) of younger participants (filled) and older participants (open) plotted as a function of audiometric frequency (Hz).

Figure 2

Effects of gap location and gap location uncertainty on gap detection thresholds. A. Individual and mean gap detection thresholds when gap location was fixed for younger adults (filled) and older adults (open). Mean gap detection thresholds were significantly larger in older than younger adults when the gap was located in the beginning of the noise. B. Individual and mean gap detection thresholds when gap location was varied from trial to trial for younger adults (filled) and older adults (open). Gap detection thresholds were significantly larger in older than younger adults when the gap was located in the beginning or end of the noise. C. Mean gap detection thresholds for younger adults (filled) and older adults (open) for the fixed conditions (circles) and random conditions (triangles). Significant differences in gap detection for fixed and random conditions were observed for older but not younger adults.

Figure 3

Individual variation in processing speed (Purdue pegboard assembly) predicts gap detection thresholds for the random condition only (r=−.68, p=.001).