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Substantial research has examined cognition in aging bilinguals. However, less work has investigated the effects of aging on language itself in bilingualism. In this article I comprehensively review prior research on this topic, and interpret the evidence in light of current theories of aging and theories of bilingualism. First, aging indeed appears to affect bilinguals' language performance, though there is considerable variability in the trajectory across adulthood (declines, age-invariance, and improvements) and in the extent to which these trajectories resemble those found in monolinguals. I argue that these age effects are likely explained by the key opposing forces of increasing experience and cognitive declines in aging. Second, consistent with some theoretical work on bilingual language processing, the grammatical processing mechanisms do not seem to change between younger and older bilingual adults, even after decades of immersion. I conclude by discussing how future research can further advance the field.
While much attention has been devoted to the cognition of aging multilingual individuals, little is known about how age affects their grammatical processing. We assessed subject-verb number-agreement processing in sixty native (L1) and sixty non-native (L2) speakers of German (age: 18-84) using a binary-choice sentence-completion task, along with various individual-differences tests. Our results revealed differential effects of age on L1 and L2 speakers' accuracy and reaction times (RTs). L1 speakers' RTs increased with age, and they became more susceptible to attraction errors. In contrast, L2 speakers' RTs decreased, once age-related slowing was controlled for, and their overall accuracy increased. We interpret this as resulting from increased L2 exposure. Moreover, L2 speakers' accuracy/RT patterns were more strongly affected by cognitive variables (working memory, interference control) than L1 speakers'. Our findings show that as regards bilinguals' grammatical processing ability, aging is associated with both gains (in experience) and losses (in cognitive abilities).
Previous research with younger adults has revealed differences between native (L1) and non-native late-bilingual (L2) speakers with respect to how morphologically complex words are processed. This study examines whether these L1/L2 differences persist into old age. We tested masked-priming effects for derived and inflected word forms in older L1 and L2 speakers of German and compared them to results from younger L1 and L2 speakers on the same experiment (mean ages: 62 vs. 24). We found longer overall response times paired with better accuracy scores for older (L1 and L2) participants than for younger participants. The priming patterns, however, were not affected by chronological age. While both L1 and L2 speakers showed derivational priming, only the L1 speakers demonstrated inflectional priming. We argue that general performance in both L1 and L2 is affected by aging, but that the more profound differences between native and non-native processing persist into old age.
Older adults demonstrate a slower speed of linguistic processing, including sentence processing. In nonlinguistic cognitive domains such as memory, research suggests that age-related slowing of processing speed may be a strategy adopted in order to avoid potential error and/or to spare “cognitive resources.” So far, very few studies have tested whether older adults’ slower processing speed in the linguistic domain has a strategic nature as well. To fill this gap, we tested whether older adults can maintain language processing accuracy when a faster processing speed is enforced externally. Specifically, we compared sentence comprehension accuracy in younger and older adults when sentences were presented at the participant’s median self-paced reading speed versus twice as fast. We hypothesized that an external speed increase will cause a smaller accuracy decline in older than younger adults because older adults tend to adopt self-paced processing speeds “further away” from their performance limits. The hypothesis was not confirmed: The decline in accuracy due to faster presentation did not differ by age group. Thus, we found no evidence for strategic nature of age-related slowing of sentence processing. On the basis of our experimental design, we suggest that the age-related slowing of sentence processing is caused not only by motor slowdown, but also by a slowdown in cognitive processing
In addition to sensory decline, age-related losses in auditory perception also reflect impairments in attentional modulation of perceptual saliency. Using an attention and intensity-modulated dichotic listening paradigm, we investigated electrophysiological correlates of processing conflicts between attentional focus and perceptual saliency in 25 younger and 26 older adults. Participants were instructed to attend to the right or left ear, and perceptual saliency was manipulated by varying the intensities of both ears. Attentional control demand was higher in conditions when attentional focus and perceptual saliency favored opposing ears than in conditions without such conflicts. Relative to younger adults, older adults modulated their attention less flexibly and were more influenced by perceptual saliency. Our results show, for the first time, that in younger adults a late negativity in the event-related potential (ERP) at fronto-central and parietal electrodes was sensitive to perceptual-attentional conflicts during auditory processing (N450 modulation effect). Crucially, the magnitude of the N450 modulation effect correlated positively with task performance. In line with lower attentional flexibility, the ERP waveforms of older adults showed absence of the late negativity and the modulation effect. This suggests that aging compromises the activation of the frontoparietal attentional network when processing the competing and conflicting auditory information.
Multitalker situations confront listeners with a plethora of competing auditory inputs, and hence require selective attention to relevant information, especially when the perceptual saliency of distracting inputs is high. This study augmented the classical forced-attention dichotic listening paradigm by adding an interaural intensity manipulation to investigate developmental differences in the interplay between perceptual saliency and attentional control during auditory processing between early and middle childhood. We found that older children were able to flexibly focus on instructed auditory inputs from either the right or the left ear, overcoming the effects of perceptual saliency. In contrast, younger children implemented their attentional focus less efficiently. Direct comparisons of the present data with data from a recently published study of younger and older adults from our group suggest that younger children and older adults show similar levels of performance. Critically, follow-up comparisons revealed that younger children's performance restrictions reflect difficulties in attentional control only, whereas older adults' performance deficits also reflect an exaggerated reliance on perceptual saliency. We conclude that auditory attentional control improves considerably from middle to late childhood and that auditory attention deficits in healthy aging cannot be reduced to a simple reversal of child developmental improvements.
Older adults often experience hearing difficulties in multitalker situations. Attentional control of auditory perception is crucial in situations where a plethora of auditory inputs compete for further processing. We combined an intensity-modulated dichotic listening paradigm with attentional manipulations to study adult age differences in the interplay between perceptual saliency and attentional control of auditory processing. When confronted with two competing sources of verbal auditory input, older adults modulated their attention less flexibly and were more driven by perceptual saliency than younger adults. These findings suggest that aging severely impairs the attentional regulation of auditory perception.
Normal aging is associated with a decline in different cognitive domains and local structural atrophy as well as decreases in dopamine concentration and receptor density. To date, it is largely unknown how these reductions in dopaminergic neurotransmission affect human brain regions responsible for reward-based decision making in older adults. Using a learning criterion in a probabilistic object reversal task, we found a learning stage by age interaction in the dorsolateral prefrontal cortex (dIPFC) during decision making. While young adults recruited the dlPFC in an early stage of learning reward associations, older adults recruited the dlPFC when reward associations had already been learned. Furthermore, we found a reduced change in ventral striatal BOLD signal in older as compared to younger adults in response to high probability rewards. Our data are in line with behavioral evidence that older adults show altered stimulus-reward learning and support the view of an altered fronto-striatal interaction during reward-based decision making in old age, which contributes to prolonged learning of reward associations.