The irrelevant speech effect among younger and older adults: The influence of background noises on reading comprehension.

BACKGROUND: Aging could exacerbate the decreases in cognitive functioning already caused by noise pollution. According to the inhibitory deficit hypothesis, older adults have more difficulty than do younger adults keeping irrelevant information from interfering with processing of relevant information. However, irrelevant speech studies typically fail to support this hypothesis. The present study aimed to quantify the effects of age and noise pollution on reading comprehension. METHODS: Seventeen younger (age 21-29) and 15 older (age 62-77) adults completed a reading task (reading discourse material for a follow-up comprehension test) in the presence of six irrelevant background noise conditions. Repeated measures ANOVAs and t tests were used to analyze participant accuracy on the follow-up comprehension tests. RESULTS: Contrary to the inhibitory deficit hypothesis, but congruent with previous irrelevant speech studies, younger and older adults did not have significantly different reading comprehension scores, and both groups' accuracy was greatest when asked to read in silence. Noise conditions that contained English speech, regardless of whether this background noise was spoken or sung, were most disruptive. CONCLUSION: Younger and older adults appear to be equally influenced by irrelevant background material when reading. Regardless of age, reading in a distraction-free environment whenever possible is the best way to maximize reading comprehension.

Making sense of age-related distractibility: the critical role of sensory modality.

Older adults are known to have reduced inhibitory control and therefore to be more distractible than young adults. Recently, we have proposed that sensory modality plays a crucial role in age-related distractibility. In this study, we examined age differences in vulnerability to unimodal and cross-modal visual and auditory distraction. A group of 24 younger (mean age=21.7 years) and 22 older adults (mean age=65.4 years) performed visual and auditory n-back tasks while ignoring visual and auditory distraction. Whereas reaction time data indicated that both young and older adults are particularly affected by unimodal distraction, accuracy data revealed that older adults, but not younger adults, are vulnerable to cross-modal visual distraction. These results support the notion that age-related distractibility is modality dependent.

The role of sensory modality in age-related distraction: a critical review and a renewed view.

Selective attention requires the ability to focus on relevant information and to ignore irrelevant information. The ability to inhibit irrelevant information has been proposed to be the main source of age-related cognitive change (e.g., Hasher & Zacks, 1988). Although age-related distraction by irrelevant information has been extensively demonstrated in the visual modality, studies involving auditory and cross-modal paradigms have revealed a mixed pattern of results. A comparative evaluation of these paradigms according to sensory modality suggests a twofold trend: Age-related distraction is more likely (a) in unimodal than in cross-modal paradigms and (b) when irrelevant information is presented in the visual modality, rather than in the auditory modality. This distinct pattern of age-related changes in selective attention may be linked to the reliance of the visual and auditory modalities on different filtering mechanisms. Distractors presented through the auditory modality can be filtered at both central and peripheral neurocognitive levels. In contrast, distractors presented through the visual modality are primarily suppressed at more central levels of processing, which may be more vulnerable to aging. We propose the hypothesis that age-related distractibility is modality dependent, a notion that might need to be incorporated in current theories of cognitive aging. Ultimately, this might lead to a more accurate account for the mixed pattern of impaired and preserved selective attention found in advancing age.

Aging and distraction by irrelevant speech: does emotional valence matter?

OBJECTIVES: From prior studies, we know that older adults are rarely more distracted by irrelevant speech than younger adults, which is remarkable in light of the inhibitory deficit view of aging. We tested the hypothesis that older adults are more distracted by emotional irrelevant speech during a visual cognitive task than younger adults. METHODS: Forty-eight younger (mean age = 21.9 years) and 48 older individuals (mean age = 68.1 years) performed a visual counting task while being exposed to irrelevant speech consisting of random numbers intermixed with neutral, positive, or negative words. Performance in these conditions was compared with that in a silence condition. RESULTS: Irrelevant speech increased counting time and decreased accuracy similarly for younger and older adults. Furthermore, the emotional conditions did not elicit a stronger effect than the neutral condition. Finally, we found implicit memory for irrelevant speech, but its level was independent of emotional valence and age. DISCUSSION: We conclude that emotional irrelevant speech has no disproportionate impact on cognitive performance in older adults. This can be regarded as a challenge to the inhibitory deficit hypothesis.

The effects of age on channel capacity for absolute identification of tonal duration.

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.

Why do older adults have difficulty following conversations?

Age-related declines in understanding conversation may be largely a consequence of perceptual rather than cognitive declines. B. A. Schneider, M. Daneman, D. R. Murphy, and S. Kwong-See (2000) showed that age-related declines in comprehending single-talker discourse could be eliminated when adjustments were made to compensate for the poorer hearing of older adults. The authors used B. A. Schneider et al.'s methodology to investigate age-related differences in comprehending 2-person conversations. Compensating for hearing difficulties did not eliminate age-related differences when the 2 talkers were spatially separated by 9 degrees or 45 degrees azimuth, but it did when the talkers' contributions came from one central location. These findings suggest that dialogue poses more of a problem for older than for younger adults, not because of the additional cognitive requirements of having to follow 2 talkers rather than 1, but because older adults are not as good as younger adults at making use of the auditory cues that are available for helping listeners perceptually segregate the contributions of 2 spatially separated talkers.

A comparison of higher order auditory processes in younger and older adults.

The authors conducted 3 experiments investigating the effects of aging on higher order auditory processes. They compared younger and older adults with respect to (a) their auditory channel capacity, (b) the extent of their top-down control over auditory gain, and (c) their ability to focus attention on a narrow band of frequencies. To ensure that subclinical cochlear processing deficits in older adults (e.g., higher thresholds, poorer discrimination of frequency and intensity differences) did not limit performance, the authors used only stimuli that were perfectly discriminable by all participants. No age differences were found in any of these experiments, suggesting that some higher order auditory processes (e.g., top-down control over auditory gain, auditory attention) are preserved in normal aging, despite numerous age-related declines in peripheral auditory functionality.

Speech comprehension difficulties in older adults: cognitive slowing or age-related changes in hearing?

Speech comprehension declines more rapidly in older adults than in younger adults as speech rate increases. This effect is usually attributed to a slowing of brain function with age. Alternatively, this Age X Speed interaction could reflect the inability of the older adult's auditory system to cope with speed-induced stimulus degradation. When the authors speeded speech in a way that produced minimal degradation, both age groups were equally affected. However, when speech was speeded using other methods, word identification declined more in older than in younger adults. Hence, auditory decline rather than cognitive slowing may be responsible for older adults' poorer performance in speeded conditions.

Top-down gain control in the auditory system: evidence from identification and discrimination experiments.

The influence of intensity range in auditory identification and intensity discrimination experiments is well documented and is usually attributed to nonsensory factors. Recent studies, however, have suggested that the stimulus range effect might be sensory in origin. To test this notion, in one set of experiments, we had listeners identify the individual tones in a set. One baseline condition consisted of identifying four 1-kHz, low-intensity tones; the other consisted of identifying four 1-kHz, high-intensity tones. In the experimental conditions, these baseline tone sets were augmented by adding a fifth tone at either 1 or 5 kHz. Added 5-kHz tones had little effect on identification accuracy for the four baseline tones. When an added 1-kHz tone differed substantially in intensity from the four baseline tones, it adversely affected performance, with the addition of a high-intensity tone to a set of low-intensity tones having a more deleterious effect than the addition of a low-intensity tone to a set of high-intensity tones. These and further results, obtained in an exploration of this asymmetrical range effect in a third identification experiment and in two intensity-discrimination experiments, were consistent with the notion of a nonlinear amplifier under top-down control whose functions include protection against sensory overload from loud sounds. The identification data were well described by a signal-detection model using equal-variance Laplace distributions instead of the usual Gaussian distributions.

Comparing the effects of aging and background noise on short-term memory performance.

Paired associate recall was tested as a function of serial position for younger and older adults for five word pairs presented aurally in quiet and in noise. In Experiment 1, the addition of noise adversely affected recall in young adults, but only in the early serial positions. Experiments 2 and 3 suggested that the recall of older adults listening to the words in quiet was nearly equivalent to that of younger adults listening in noise. In Experiment 4, we determined the signal-to-noise ratio (S/N) such that, on average, younger and older adults were able to correctly hear the same percentage of words when words were presented one at a time in noise. In Experiment 5, younger adults were tested under this S/N. Compared with older adults from Experiment 3, younger adults in this experiment recalled more words at all serial positions. The results are interpreted as showing that encoding in secondary memory is impaired by aging and noise either as a function of degraded sensory representations, or as a function of reduced processing resources.