The effects of total sleep deprivation on the generation of random sequences of key-presses, numbers and nouns

According to a recent hypothesis, executive functions should be particularly vulnerable to the effects of total sleep deprivation. Random generation is a task that taps executive functions. In three experiments we examined the effects of total sleep deprivation on random generation of keypresses, numbers, and nouns, in particular on the suppression of prepotent responses and the selection of next responses by way of applying a local-representativeness heuristic. With random key-presses suppression of prepotent responses did not suffer from lack of sleep, but it became poorer at a sufficiently high pacing rate. In contrast, suppression of prepotent responses suffered when numbers and nouns were generated. According to these findings different types of random generation tasks involve different types of inhibitory process. With only four response alternatives, but not with larger response sets, application of the local-representativeness heuristic was impaired after a night without sleep. In terms of a simple formal model, serial-order representations of the preceding responses are used in selecting the next response only for the small response set, and not for larger response sets. Thus, serial-order representations are likely to suffer from loss of sleep. These findings strongly suggest that random generation involves multiple processes and that total sleep deprivation does not impair all sorts of executive functions, but only some.     

No evidence of age-related increases in unconscious plagiarism during free recall

In three experiments younger and older participants took part in a group generation task prior to a delayed recall task. In each, participants were required to recall the items that they had generated, avoiding plagiarism errors. All studies showed the same pattern: older adults did not plagiarise their partners any more than younger adults did. However, older adults were more likely than younger adults to intrude with entirely novel items not previously generated by anyone. These findings stand in opposition to the single previous demonstration of age-related increases in plagiarism during recall.     

No evidence of age-related increases in unconscious plagiarism during free recall

In three experiments younger and older participants took part in a group generation task prior to a delayed recall task. In each, participants were required to recall the items that they had generated, avoiding plagiarism errors. All studies showed the same pattern: older adults did not plagiarise their partners any more than younger adults did. However, older adults were more likely than younger adults to intrude with entirely novel items not previously generated by anyone. These findings stand in opposition to the single previous demonstration of age-related increases in plagiarism during recall.     

Age-related differences in idea generation and selection for propositional language

Conceptual preparation mechanisms such as novel idea generation and selection from amongst competing alternatives are critical for language production and may contribute to age-related language deficits. This study investigated whether older adults show diminished idea generation and selection abilities, compared to younger adults. Twenty younger (18–35 years) and 20 older (60–80 years) adults completed two novel experimental tasks, an idea generation task and a selection task. Older participants were slower than younger participants overall on both tasks. Importantly, this difference was more pronounced for task conditions with greater demands on generation and selection. Older adults were also significantly reduced on a semantic, but not phonemic, word fluency task. Overall, the older group showed evidence of age-related decline specific to idea generation and selection ability. This has implications for the message formulation stage of propositional language decline in normal aging.     

Aging and implicit learning: explorations in contextual cuing

In contextual cuing, faster responses are made to repeated displays containing context-target associations than to novel displays without such covariances. We report that healthy older adults showed learning impairments in contextual cuing when compared with younger adults. The display properties in the task were altered to artificially increase younger adults' response times to match those of older adults and to produce faster responses in older participants; however, younger participants' learning remained intact, whereas older participants continued to show impairments under these conditions. These results suggest that older adults have intrinsic deficits in contextual cuing that cannot be attributed to their slower overall response speed.     

The role of age and perceptual symbols in language comprehension

Older and younger participants read sentences about objects and were then shown a picture of an object that either matched or mismatched the implied shape of the object in the sentence. Participants' response times were recorded when they judged whether the object had been mentioned in the sentence. Responses were faster in the shape-matching condition for all participants, but the mismatch effect was stronger for older than for younger adults, even when the larger variability of the older group's response times was controlled for. These results suggest that older adults may construct stronger situation models than younger adults.     

Suppression of reflexive saccades in younger and older adults: Age comparisons on an antisaccade task

Inhibitory control of prepotent responses has been examined by using the antisaccade task, during which a reflexive saccade toward a peripheral onset must be suppressed before an eye movement in the opposite direction from the onset can be executed. In the present experiments, we sought to determine whether older and younger adults would perform similarly on this task. Older adults had a harder time suppressing their reflexive responses, as measured by an increase in the proportion of saccade direction errors. Despite an age-related decline in saccade direction accuracy, the increase in saccade latency associated with the antisaccade condition was the same for both younger and older adults. These results support the view that the effectiveness of inhibitory control declines with age (Hasher & Zacks, 1988; Hasher, Zacks, & May, 1999).     

Age, Race, and Implicit Prejudice: Using Process Dissociation to Separate the Underlying Components

ABSTRACT— Older adults express greater prejudice than younger adults, but it is not clear why. In a community-based sample, we found that older White adults demonstrated more racial prejudice on an implicit measure, the race Implicit Association Test, than did younger adults. Process-dissociation procedures indicated that this difference in implicit prejudice was due to older adults having less control of their automatic prejudicial associations rather than stronger automatic prejudicial associations. Furthermore, this age difference in control was mediated by age-related deficits in inhibitory ability. White participants showed stronger automatic prejudicial associations than did Black participants.     

Age,working memory,and the Tower of London task

The current study explores the role of three components of working memory in age differences in an executive task, the Tower of London (TOL). The TOL task is sensitive to frontal lobe damage, and is widely used to measure planning ability. Dual tasks were used to test the involvement of the phonological loop (articulatory suppression), visuospatial buffer (pattern tapping), and central executive (random generation) in age effects on the TOL. Older adults showed greater reliance than young on domain-specific verbal and spatial memory components in performing the TOL. In terms of executive function, qualitatively different interference patterns were seen in young and old participants. However, the validity of using random generation tasks to assess executive function in older populations can be questioned. For older participants, performing the TOL loads all components of working memory, whereas for the younger participants the TOL more specifically loads executive functioning.     

Adult Age Differences in Memory for Verbs and Nouns

Younger and older adults were asked to remember noun pairs (e.g., head – cap), verb pairs (e.g., bounce – throw), and verb-noun pairs (e.g., break – stick). For half of the pairs, participants used imagined objects and performed an action or series of related actions for each pair. For the other half of the pairs, participants read but did not perform the pairs. Free recall and cued recall tests revealed that age differences in memory for both performed and nonperformed items were larger for verbs than for nouns. The recall advantage of nouns over verbs was larger for older than for younger adults. Verbs are hypothesized to be more difficult for older adults to remember because they are more and less specific than nouns and because it is more difficult to integrate verbs with other words than to integrate nouns with other words.     

Lexical access in younger and older adults: the case of the mass/count distinction.

Although lexicosemantic deficits are not typically seen in older adults, some studies indicate that age-related changes in semantic processing may occur. We had groups of older and younger adults perform speeded lexical decision on mass (e.g., honey), count (e.g., car), and dual nouns, which may be either mass or count (e.g., lamb). Singular dual nouns engendered significantly faster response times in older adults than mass and count nouns, whereas younger adults manifested similar response times to count and dual nouns. These results point toward a three-way distinction in the lexicon between mass, count, and dual nouns. Older adults appear to treat a larger set of nouns as dual than do younger adults. This may be due to awareness of the mass/count ambiguity present in a greater number of lexical items, as a result of their greater linguistic experience. Alternatively, in order to conserve processing resources, older adults may not activate mass/count information when recognizing a dual noun unless a mass or count reading is forced by context.     

Age differences in recollection: three patterns of enhanced encoding

Memory encoding conditions can be manipulated in a variety of ways, and many of these methods result in improved recollection for both younger and older adults relative to baseline conditions. Previous results have shown differential age-related patterns of improvement, however, with some manipulations giving equal improvement to young and old participants, some benefiting older adults more, and others benefiting younger adults more. In 2 experiments, the authors show that presenting pictures with words benefited older more than younger participants, word generation benefited both groups equally, and an encoding condition requiring novel integrative processing benefited younger more than older adults. The authors discuss these results in terms of the enhanced elaboration afforded and processing demanded by differential combinations of age groups and encoding conditions.     

Age-Related Changes in Neural Activation During Working Memory Performance

Changes in frontal lobe functions are a typical part of aging of the brain. There are age-related declines in working memory performance, a skill requiring frontal lobe activation. This study examined neural activation, using [15 O] water positron emission tomography (PET) methodology, during performance on two verbal working memory tasks in younger and older participants. The results demonstrated the typical areas of activation associated with working memory performance (e.g., dorsolateral prefrontal cortex and inferior parietal cortex) in both groups. However, the younger participants utilized the right dorsolateral prefrontal cortex and anterior cingulate gyrus significantly more than the older participants. In turn, the older participants used the left dorsolateral prefrontal cortex significantly more than the younger participants and maintained material-specific lateralization in their pattern of activation. These findings are consistent with a previous report of different age-related patterns of frontal activation during working memory.     

Ageing, remembering, and executive function

This study was designed to investigate the relationship between executive functions and the age-related decline in episodic memory through the states-of-awareness approach. Following the presentation of a word list, a group of younger adults and a group of older adults undertook a recognition test in which they classified their responses according to the Remember-Know-Guess procedure (Gardiner & Richardson-Klavehn, 2000). In order to operationalise the executive function hypothesis, we investigated three specific executive functions (updating, shifting, and inhibition of a prepotent response) described in Miyake et al.'s (2000) theoretical model, and a complex executive task. The results revealed that fewer "R" responses were made during the recognition test by the older than the younger group, whereas there was no difference between the groups in the number of "K" responses. In addition, correlations indicated that remembering depended on executive function measures, whereas knowing did not. The hierarchical regression analyses showed that controlling for executive function, and particularly for the 2-back test, largely removed the age-related variance in remembering. These findings support the notion that executive dysfunction, and specifically updating decline, plays a central role in age-related memory loss.     

Age deficits in the control of prepotent responses: evidence for an inhibitory decline

Older adults have more difficulty than younger adults appropriately directing their behavior when the required response is in competition with a prepotent response. The authors varied the difficulty of inhibiting a prepotent eye movement response by varying the response cue (peripheral onset or central arrow). The response cue manipulation did not affect prosaccade accuracy and latency for either age group and did not affect younger adults' antisaccades. Older adults' antisaccades were slower in the peripheral cue condition than in the central arrow condition. These findings are taken as support for the inhibitory deficit hypothesis of aging (L. Hasher, R. T. Zacks, & C. P. May, 1999).     

Selection demands versus association strength in the verb generation task

Neuroimaging and neuropsychological data from Thompson-Schill and colleagues (Thompson-Schill, D’Esposito, Aguirre, & Farah, 1997; Thompson-Schill et al., 1998) showed that in the verb generation task, the left inferior frontal gyrus (left IFG) was more involved in a high-selection condition, in which the noun had two verb responses of equal association strength, than in a low-selection condition, in which the noun had only one strongly associated verb. They proposed that the left IFG was involved in selecting semantic information from competing alternatives. The present study compared verb generation in two high-selection conditions that varied in the association strength of the most frequently produced verbs. The results from neurally intact participants and a patient with a lesion that included the left IFG indicated that association strength between nouns and the most frequently produced verb, rather than competition during verb selection, affected verb generation. The degree of involvement of the left IFG may depend on the difficulty of verb retrieval as reflected in association strength.     

The temporal distribution of autobiographical memory: changes in reliving and vividness over the life span do not explain the reminiscence bump

When autobiographical memories are elicited with word cues, personal events from middle childhood to early adulthood are overrepresented compared to events from other periods. It is, however, unclear whether these memories are also associated with greater recollection. In this online study, we examined whether autobiographical memories from adolescence and early adulthood are recollected more than memories from other lifetime periods. Participants rated personal events that were elicited with cue words on reliving or vividness. Consistent with previous studies, most memories came from the period in which the participants were between 6 and 20 years old. The memories from this period were not relived more or recalled more vividly than memories from other lifetime periods, suggesting that they do not involve more recollection. Recent events had higher levels of reliving and vividness than remote events, and older adults reported a stronger recollective experience than younger adults.     

Influence of response prepotency strength, general working memory resources, and specific working memory load on the ability to inhibit predominant responses: a comparison of young and elderly participants

One conception of inhibitory functioning suggests that the ability to successfully inhibit a predominant response depends mainly on the strength of that response, the general functioning of working memory processes, and the working memory demand of the task (Roberts, Hager, & Heron, 1994). The proposal that inhibition and functional working memory capacity interact was assessed in the present study using two motor inhibition tasks (Go/No-Go and response incompatibility) in young and older participants. The strength of prepotency was assessed with a short or long training phase for the response to be inhibited. The influence of working memory resources was evaluated by administering the tasks in full vs. divided attention conditions. The effect of working memory load was manipulated by increasing the number of target and distracter items in each task. Results showed no effect of prepotency strength, whereas dividing attentional resources and increasing working memory load were associated with greater inhibitory effects in both groups and for both tasks. This deleterious effect was higher for older participants, except in the working memory load condition of the Go/No-Go task. These results suggest an interactive link between working memory and response inhibition by showing that taxing working memory resources increases the difficulty of inhibiting prepotent responses in younger and older subjects. The additional detrimental effect of these factors on healthy elderly subjects was related to their decreased cognitive resources and to their shorter span size.     

Success and failure at dual-task coordination by younger and older adults

Dual-task processing was explored in younger and older adults in 2 experiments that used a tone discrimination and a letter discrimination task. To encourage parallel processing if that was possible, the authors presented the stimuli for the 2 tasks simultaneously, and participants were instructed to withhold their responses until both were ready. The authors found no evidence for parallel processing and no evidence that the management of central processing of dual tasks is qualitatively different in older adults than it is in younger adults. When one response was verbal and the other manual, the 2 responses closely coincided. When both responses were manual, the authors did find that the first response was not delayed enough to coincide with the 2nd and that this underestimation was greater in older adults.