Academic journal article Attention, Perception and Psychophysics

The Effects of Age on Channel Capacity for Absolute Identification of Tonal Duration

Academic journal article Attention, Perception and Psychophysics

The Effects of Age on Channel Capacity for Absolute Identification of Tonal Duration

Article excerpt

We compared the ability of younger and older adults to identify which 2-kHz tones of eight varying durations was presented on a trial with their ability to discriminate between adjacent pairs of duration-varying tones drawn from the same set. We used signal detection analyses to construct scales of perceived duration for both tasks. Scales derived from pairwise comparisons of adjacent durations were related linearly to the logarithm of stimulus duration; these were essentially identical in younger and older adults. However, scales derived from the eight-alternative absolute identification experiments, which were also linearly related to the logarithm of duration, indicated that older adults outperformed younger adults on this task. These results suggest that the ability to process large numbers of stimuli that differ only in duration is at least as good, if not better, in older than in younger adults, relative to the ability of each group to discriminate between two stimuli differing only in duration.

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To extract and process attended stimuli when the listening situation is poor (e.g., when there are competing sound sources or there is excessive reverberation), listeners often need to engage higher order, more central processing mechanisms. By focusing their attention on particular frequency regions, by inhibiting irrelevant signals, and by using context to disambiguate signals, listeners are often able to recover information that is degraded or lost at the sensory level. Because of age-related declines in hearing, older adults are more likely than younger adults are to have to engage these higher order processes in order to function in everyday listening situations (see Schneider, Pichora- Fuller, & Daneman, 2009, for a review). Consequently, they may become more skilled at operating under such conditions than younger adults, provided that the relevant higher order central processes are preserved in old age. Indeed, there is evidence that older adults benefit more from context than do younger adults in difficult listening situations (Pichora-Fuller, Schneider, & Daneman, 1995; Sheldon, Pichora-Fuller, & Schneider, 2008), suggesting that, not only is the ability to use context to disambiguate signals preserved in old age, but older adults become more skilled in its employment.

Given that there are large and obvious declines with age in peripheral auditory processes (Murphy, Schneider, Speranza, & Moraglia, 2006; Schneider & Pichora-Fuller, 2000), it also may be that some higher order or more central auditory and cognitive processes decline with age. If they do, the auditory processing abilities of older adults would be doubly compromised-first, by cochlear degeneration, and second, by age-related changes in retrocochlear auditory processes. Although there is considerable evidence that age-related cochlear degeneration greatly reduces the spectral and temporal resolution of the auditory system (see Schneider, 1997; Schneider & Pichora-Fuller, 2000, 2001, for recent reviews), thereby compromising the signal at the level of the cochlea, the evidence concerning age-related changes in retrocochlear processes in healthy aging is sparse. For example, Ison, Virag, Allen, and Hammond (2002) and Murphy et al. found no evidence of age-related changes in auditory attention bands-that is, changes in the ability of older adults to focus their attention on a particular frequency range. In addition, Murphy et al. failed to find any evidence for age-related declines in top-down gain control-that is, in the ability of the auditory system to adjust its gain to accommodate different listening situations. A number of studies have shown that there is a nonlinear amplifier within the auditory system that amplifies very low-intensity stimuli and attenuates high-intensity stimuli, thereby extending the range over which the auditory system can respond (Brownell, 1997; Gordon & Schneider, 2007; Parker, Murphy, & Schneider, 2002; Robles & Ruggero, 2001; Yates, 1995). …

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