Young normal-hearing listeners, elderly normal-hearing listeners, and elderly hearing-impaired listeners were tested on a variety of phonetic identification tasks. Where identity was cued by stimulus duration, the elderly hearing-impaired listeners evidenced normal identification functions. On a task in which there were multiple cues to vowel identity, performance was also normal. On a/b d g/identification task in which the starting frequency of the second formant was varied, performance was abnormal for both the elderly hearing-impaired listeners and the elderly normal-hearing listeners. We conclude that errors in phonetic identification among elderly hearing-impaired listeners with mild to moderate, sloping hearing impairment do not stem from abnormalities in processing stimulus duration. The results with the /b d g/continuum suggest that one factor underlying errors may be an inability to base identification on dynamic spectral information when relatively static information, which is normally characteristic of a phonetic segment, is unavailable.

The effects of mild-to-moderate hearing impairment on the perceptual importance of three acoustic correlates of stop consonant place of articulation were examined. Normal-hearing and hearing-impaired adults identified a stimulus set comprising all possible combinations of the levels of three factors: formant transition type (three levels), spectral tilt type (three levels), and abruptness of frequency change (two levels). The levels of these factors correspond to those appropriate for /b/, /d/, and /g/ in the /ae/ environment. Normal-hearing subjects responded primarily in accord with the place of articulation specified by the formant transitions. Hearing-impaired subjects showed less-than-normal reliance on formant transitions and greater-than-normal reliance on spectral tilt and abruptness of frequency change. These results suggest that hearing impairment affects the perceptual importance of cues to stop consonant identity, increasing the importance of information provided by both temporal characteristics and gross spectral shape and decreasing the importance of information provided by the formant transitions.

Comparisons were made between groups of old and young subjects in a dichotic task. In the first experiment old and young subjects had digit spans representative of their respective populations, and in accord with previous dichotic research younger subjects recalled with greater accuracy. The main effect of group and the Group x Test (ear reported first vs ear reported second) interaction were reliable with both serial and free recall scoring. In the second experiment young subjects were matched to old subjects on the basis of digit span. Matching eliminated the group and Group x Test interaction with seriall recall and the group effect with free recall, suggesting that digit span and dichotic memory are mediated by common mechanisms. Error trends and the Group x Test interactions with free recall revealed that some age related differences persisted even after matching. These differences are discussed in terms of regression artifact and processing capacity.

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Comparisons were made of the response latencies of old (mean age = 69.2 years) and young (mean age = 26.8 years) subjects on simple and choice reaction time (RT) tasks and "physical identity" (PI) and "name identity" (NI) trials of a letter-matching task. Young subjects were faster than old subjects on all tasks, and the absolute difference between groups increased with processing complexity (simple RT < choice RT < PI < NI). However, in support of the hypothesis that aging is associated with a general reduction in processing speed, the relative difference between groups did not vary with task, except for a subset of the NI trials. Response latencies for the NI trials varied with stimulus letter for both age groups, but the magnitude of the letter effect was greater for the elderly. Their latencies were disproportionately long for the more difficult letters. A second experiment showed that NI latency reflected the visual similarity of the letters with respect to the other letters in the stimulus set. It is suggested, therefore, that the NI letter effect resulted from differences in letter identification time. The disproportionately long latencies of the elderly for the visually similar letters are discussed in terms of the hypothesis that aging is associated with an increase in internal noise.283