抑制和加工速度与液态智力的年老化

研究抑制能力和加工速度在液态智力年老化过程中的相对作用。被试为142名18~85岁健康成年人,完成包括抑制优势反应、加工速度和液态智力共13项测验。分层回归分析显示,抑制能力与年龄相关的特异性变异,在控制简单的速度变量时较控制复杂的速度变量时更大;结构方程分析表明,对液态智力年老化的中介作用,当选取较复杂的速度变量时加工速度的作用更大,而当选取较简单的速度变量时抑制能力的作用更大。研究结果表明,在液态智力的年老化过程中,除了加工速度的作用之外,抑制能力也起重要的中介作用。该结果为认知年老化的抑制理论和执行衰退假说提供了认知行为学研究的证据,并且对加工速度理论作了有益的补充和修正     

Why do older adults have difficulty with semantic fluency?

Aging involves many cognitive declines, particularly in fluid intelligence, with relative maintenance of crystallized intelligence. This paradox is evident in the language domain: lexical retrieval becomes slower and less accurate, despite well preserved vocabularies. Verbal fluency assesses both crystallized and fluid aspects of language. Semantic fluency hypothetically reflects semantic knowledge, while letter fluency putatively reflects executive functioning, which would predict a greater impact of aging on the latter. However, the opposite is typically observed.

To investigate factors contributing to such asymmetries, we examined verbal fluency in 86 adults (30-89 years). Multiple regression analyses indicated that semantic fluency depends largely on lexical retrieval speed, as well as visualization strategies to support controlled retrieval, skills which may disproportionately decline with age. By contrast, letter fluency relies heavily on vocabulary knowledge, providing some protection against age-related declines. These findings contribute to our understanding of the mechanisms of typical age-related declines in word retrieval.     

Performance of healthy, older adults on the Tower of London Revised: Associations with verbal and nonverbal abilities

Neuropsychological studies suggest a subclinical impairment in executive function that occurs with normal aging. This is the first study to examine the performance of healthy older adults on the Tower of London-Revised (TOL-R), as well as the relationship between TOL-R performance and verbal and nonverbal abilities. Performance of 63 older adult participants on the TOL-R and two WAIS-III subtests was compared to that of 35 young adult college students. Group comparisons indicated age differences in TOL-R performance; however, these were eliminated after adjusting for individual differences in Matrix Reasoning performance. In the older adult groups, multiple regression analyses demonstrated that Matrix Reasoning performance was a stronger predictor of TOL-R performance than was chronological age or years of education. These results suggest that performance on the TOL-R is a psychometrically sound executive function measure for older adults and that individual differences in fluid intelligence are more predictive of performance than chronological age.     

Differential trajectories of age-related changes in components of executive and memory processes

Several studies have demonstrated age-related declines in general executive function and memory. In this study, we examined cross-sectional and longitudinal age effects in more specific cognitive processes that constitute executive function and memory. We postulated that, whereas some components of executive and memory functions would show age differences and longitudinal declines, other specific abilities would be maintained or even improve with repeated testing. In a sample of individuals ≥55 years old from the Baltimore Longitudinal Study of Aging, we found longitudinal declines in inhibition, manipulation, semantic retrieval, phonological retrieval, switching, and long-term memory over a maximum of 14 years follow-up. In contrast, abstraction, capacity, chunking, discrimination, and short-term memory were maintained or even improved longitudinally, probably due in part to repeated testing. Moreover, whereas several different abilities were correlated across participants' cross-sectional performance, longitudinal changes in performance showed more heterogeneous trajectories. Finally, compared with cross-sectional performance, longitudinal trajectories showed better distinction between participants with and those without later cognitive impairment. These results show that longitudinal cognitive aging of executive and memory functions is not a uniform process but a heterogeneous one and suggest that certain executive and memory functions remain stable despite age-related declines in other component processes. (PsycINFO Database Record (c) 2012 APA, all rights reserved).     

Executive functioning as a mediator of the relationship between age and episodic memory in healthy aging

The extent to which age-related differences in executive functioning account for age-related differences in recall from episodic memory was examined in a group of healthy older adults. Fifty-one subjects between the ages of 60 and 91 years were given tests of general cognitive abilities, episodic memory, and executive functioning. A mediational model was proposed with executive functioning as the mediator of the relationship between age and delayed recall. Consistent with this model, regression analyses indicated that, when considered alone, age was a significant predictor of recall (p <.001); however, age was not a significant predictor of recall when the effect of executive functioning was partialled out of the equation (p=.37). Furthermore, the unique contribution of executive functioning accounted for 36% of the variance in recall performance. A significant portion of age-related differences in episodic memory recall, therefore, may be due to age-related differences in the executive skills required for optimal performance on such tests.     

Adult Age Differences in Tower of Hanoi Performance: Influence From Demographic and Cognitive Variables

We examined performance in a five-disk version of the Tower of Hanoi (TOH) puzzle, assumed to reflect executive functioning, in population-based samples ranging in age from 35 to 85 years (N ?=?2798). Univariate analyses revealed significant age effects across three TOH measures as reflected by an age-related increase in moves to solution, a gradual slowing of performance, and an increase in rule violations with advanced age. The age-related influence was eliminated, or reduced considerably, when controlling for demographic and cognitive background variables. Across the dependent measures, Block Design and a measure of episodic memory (recall) were the consistent predictors. No effects of education were detected, while significant gender differences, favoring males, were observed for two TOH measures. Taken together, the results suggest that age-related deficits observed in TOH performance reflects an age-related impairment in visuospatial ability in addition to impairments in executive functions.     

Executive functioning and processing speed in age-related differences in memory: Contribution of a coding task

The aim of the present study was to examine executive dysfunctioning and decreased processing speed as potential mediators of age-related differences in episodic memory. We compared the performances of young and elderly adults in a free-recall task. Participants were also given tests to measure executive functions and perceptual processing speed and a coding task (the Digit Symbol Substitution Test, DSST). More precisely, we tested the hypothesis that executive functions would mediate the age-related differences observed in the free-recall task better than perceptual speed. We also tested the assumption that a coding task, assumed to involve both executive processes and perceptual speed, would be the best mediator of age-related differences in memory. Findings first confirmed that the DSST combines executive processes and perceptual speed. Secondly, they showed that executive functions are a significant mediator of age-related differences in memory, and that DSST performance is the best predictor.     

Cognitive functioning in healthy older adults aged 64-81: a cohort study into the effects of age, sex, and education

The objective of this study was to determine a possible differential effect of age, education, and sex on cognitive speed, verbal memory, executive functioning, and verbal fluency in healthy older adults. A group of 578 healthy participants in the age range of 64-81 was recruited from a large population study of healthy adults (Maastricht Aging Study). Even in healthy individuals in this restricted age range, there is a clear, age-related decrease in performance on executive functioning, verbal fluency, verbal memory, and cognitive speed tasks. The capacity to inhibit information is affected most. Education had a substantial effect on cognitive functioning: participants with a middle or high level of education performed better on cognitive tests than did participants with a low level of education. Women performed better than men on verbal memory tasks. Therefore, education and sex must be taken into account when examining an older individual's cognitive performance.     

Construct validity and age sensitivity of prospective memory

We administered four prospective memory tasks to 330 adults between 18 and 89 years of age to investigate the relationship among the measures of performance in the four tasks, as well as the relationship of the prospective memory measures to age, other cognitive abilities, and noncognitive factors. The four prospective memory variables were found to exhibit both convergent and discriminant validity, indicating that prospective memory ability appears to represent a distinct dimension of individual differences. The prospective memory construct was significantly related to other cognitive abilities, such as executive functioning, fluid intelligence, episodic memory, and perceptual speed, but it was only weakly related to self-ratings of (primarily retrospective) memory and to personality traits. Although a substantial proportion of the age-related variance on the prospective memory construct was shared with other cognitive abilities, we also found some evidence of unique, statistically independent, age-related influences on prospective memory.     

Influences of item organizability and semantic retrieval cues on word recall in very old age

Abstract

This research investigated the influence of organizational structure in the materials and category cues at retrieval on episodic memory performance in very old age. A community-based sample of healthy, very old adults (N = 224) between 75 and 96 years was presented with two lists of words: a list of semantically unrelated words and a list of words from four taxonomic categories randomly intermixed. Free recall was assessed for both tasks and, for the organizable list, subjects received a cued recall test as well. Results showed an overall age-related deterioration of memory performance, although the ability to utilize item organizability and retrieval cues remained intact across age. Evidence from data on memory performance, as well as analyses of the nature of organizable free recall, suggests that problems at both encoding and retrieval may underlie the age-related performance deficit. In addition, there were age-related increases in (a) forgetting between free and cued recall, and (b) intrusion errors. Finally, regression analyses indicated that, in addition to age, level of schooling as well as markers of general cognitive status (the Mini-Mental State Examination) and fluid intelligence (Block Design) accounted for performance variation across all memory tasks.     

The influence of functional social support on executive functioning in middle-aged African Americans

Social support has a positive influence on cognitive functioning and buffers cognitive decline in older adults. This study examined the relations between social support and executive functioning in middle-aged adults. A community-based sample of African Americans completed the Interpersonal Support Evaluation List, a measure of functions of social support, and two measures of executive functioning, the Stroop Color and Word Test and the Wisconsin Card Sorting Test (WCST). Hierarchical regression analyses were used to explore the hypothesis that different facets of perceived social support influence performance on measures of executive functioning. After controlling for age, gender, and education, social support facets including belonging support, self-esteem support, appraisal support, and tangible support were significant predictors of Stroop performance. In addition, tangible support significantly predicted WCST performance. These findings add to previous literature on social support and cognition; however, findings for middle-aged adults are unique and suggest that social support has a positive influence on some executive functions in African Americans prior to old age.     

The influence of functional social support on executive functioning in middle-aged African Americans

ABSTRACT

Social support has a positive influence on cognitive functioning and buffers cognitive decline in older adults. This study examined the relations between social support and executive functioning in middle-aged adults. A community-based sample of African Americans completed the Interpersonal Support Evaluation List, a measure of functions of social support, and two measures of executive functioning, the Stroop Color and Word Test and the Wisconsin Card Sorting Test (WCST). Hierarchical regression analyses were used to explore the hypothesis that different facets of perceived social support influence performance on measures of executive functioning. After controlling for age, gender, and education, social support facets including belonging support, selfesteem support, appraisal support, and tangible support were significant predictors of Stroop performance. In addition, tangible support significantly predicted WCST performance. These findings add to previous literature on social support and cognition; however, findings for middle-aged adults are unique and suggest that social support has a positive influence on some executive functions in African Americans prior to old age.     

Tai Chi exercise training enhances executive function and fluid intelligence of healthy older adults: Cross-sectional and longitudinal evidence

Executive function and fluid intelligence are two of the crucial frontal lobe functions susceptible to aging. Tai Chi as a mind-body exercise has been proposed for preventing cognitive aging. However, whether Tai Chi has similar effects on multiple components of executive functions in older adults remains underspecified. Moreover, it is not currently known whether Tai Chi exercise training improvements in lower-order executive functions are able to explain improvements in higher-order fluid intelligence. Study 1 included a cross-sectional design based on a large sample of healthy older adults (55–79 years old). Modeling results showed that experience of Tai Chi training exerted significantly positive effects on fluid intelligence, inhibition and updating after controlling for age and education. Both inhibition and updating mediated effects of Tai Chi on fluid intelligence. Study 2 carried out a 12-month Tai Chi training intervention on a novice group and an experienced group of older adults. Results indicated that only the novices exhibited significant improvements in inhibition and fluid intelligence. In addition, improvements in fluid intelligence were no longer significant after controlling for improvements in inhibition. These results shed lights on the mechanism by which mind-body training enhances intelligence.     

Effortful semantic decision-making boosts memory performance in older adults

A major concern in age-related cognitive decline is episodic memory (EM). Previous studies indicate that both resource and binding deficits contribute to EM decline. Environmental support by task manipulations encouraging stronger cognitive effort and deeper levels of processing may facilitate compensation for these two deficits. To clarify factors that can counteract age-related EM decline, we assessed effects of cognitive effort (four levels) and level of processing (LoP, shallow/deep) during encoding on subsequent retrieval. Young (YAs, N?=?23) and older (OAs, N?=?23) adults performed two incidental encoding tasks, deep/semantic and shallow/perceptual. Cognitive effort was manipulated by varying decision-making demands. EM performance, indexed by d-prime, was later tested using a recognition task. Results showed that regardless of LoP, increased cognitive effort caused higher d-primes in both age groups. Compared to YAs, OAs showed a lower d-prime after shallow encoding across all cognitive effort levels, and after deep encoding with low cognitive effort. Deep encoding with higher levels of cognitive effort completely eliminated these age differences. Our findings support an environmental-compensatory account of cognitive ageing and can have important therapeutic implications.     

Can longitudinal changes in processing speed explain longitudinal age changes in fluid intelligence?

The processing-speed theory of cognitive aging contends tha age-related declines in intellectual function reflect the consequences of age-related slowing of processing speed. Cross-sectional data support this assumption. The association between 4-year changes in processing speed and 4-year changes in fluid intelligence was examined with a sample of 417 older adults. Changes in processing speed correlated .53 with changes in fluid intelligence. The difference in the explanatory power of processing speed regarding age-related differences and age-related changes is discussed with reference to other longitudinal studies and methodological considerations.     

Environmental topography and postural control demands shape aging-associated decrements in spatial navigation performance

This study tests the hypothesis that aging-induced cognitive permeation of sensorimotor functions contributes to adult age differences in spatial navigation performance. Virtual maze-like museums were projected in front of a treadmill. Sixteen 20-30-year-old men and sixteen 60-70-year-old men performed a way-finding task in city-block or variable topographies while walking with or without support. Walking support attenuated age-related decrements in navigational learning. Navigation load increased trunk-angle variability for older adults only. Age differences in spatial knowledge persisted despite perfect place-finding performance. City-block topography was easier than variable topography for younger adults only, indicating age-related differences in reliance on spatial relational learning. Attempts at supporting older adults' navigation performance should consider sensorimotor/cognitive interactions and qualitative differences in navigational activity.     

Can fluid intelligence be reduced to ‘simple’ short-term storage?

Much is written regarding the associations between human intelligence and cognition. However, it is unusual to find comprehensive studies. Here twenty four measures tapping eight cognitive abilities and skills are considered for assessing a sample of one hundred and eighty five young adults. The simultaneous relationships among fluid, crystallized, and spatial intelligence, along with short-term memory, working memory capacity, executive updating, attention, and processing speed are analyzed using a latent-variable approach. The key findings show that (a) short-term storage, working memory, and updating are hardly distinguishable, and (b) fluid intelligence is near-perfectly correlated with these three cognitive functions. It is concluded that this nuclear intelligence component can be largely identified with basic and general short-term storage processes, namely, encoding, maintenance, and retrieval.     

Executive functioning and memory as potential mediators of the episodic feeling-of-knowing accuracy

The study focused on the cognitive determinants of the accuracy of feeling-of-knowing (FOK) judgments made on episodic memory information. An individual differences approach was used on a sample of healthy older adults assessed on an episodic FOK task and on several neuropsychological measures. At a global level of analysis of FOK accuracy, the contributions of four general cognitive processes--episodic memory, executive functioning, fluid intelligence and processing speed--were examined concurrently. Stepwise regression analyses showed that executive functioning accounted for the major part of variance on FOK accuracy, followed by a significant contribution of episodic memory. After controlling for executive and memory involvement, fluid intelligence and processing speed no longer accounted for significant variance. At a more detailed level of analysis of FOK accuracy, the contributions of three specific executive processes--shifting, updating and inhibition--were assessed. The results revealed shifting function as the primary executive process engaged in the production of accurate FOK judgments in episodic memory. Some hypotheses are put forward to better understand the central role of executive functioning in the production of accurate FOK judgments.     

Working memory and phonological processing as predictors of children’s mathematical problem solving at different ages

The study explored the contribution of working memory (WM) to mathematical problem solving in younger (8-year-old) and older (11-year-old) children. The results showed that (1) significant age-related differences in WM performance were maintained when measures of phonological processing (i.e., digit naming speed, short-term memory, phonological deletion) were partialed from the analysis; (2) WM predicted solution accuracy of word problems independently of measures of problem representation, knowledge of operations and algorithms, phonological processing, fluid intelligence, reading, and math skill; and (3) a second-order WM factor was correlated with problem solving, suggesting that a general or executive system underlies age-related performance. The results were interpreted as support for the notion that the executive system was an important predictor of age-related changes in problem solving beyond the contribution of math and reading skills, and this system operates independently of the phonological system and domain-specific knowledge in predicting solution accuracy.     

Task coordination and aging: explorations of executive control processes in the task switching paradigm.

A number of models of cognitive aging suggest that older adults exhibit disproportionate performance decrements on tasks which require executive control processes. In a series of three studies we examined age-related differences in executive control processes and more specifically in the executive control processes which underlie performance in the task switching paradigm. Young and old adults were presented with rows of digits and were required to indicate whether the number of digits (element number task) or the value of the digits (digit value task) were greater than or less than five. Switch costs were assessed by subtracting the reaction times obtained on non-switch trials from trials following a task switch. Several theoretically interesting results were obtained. First, large age-related differences in switch costs were found early in practice. Second, and most surprising, after relatively modest amounts of practice old and young adults switch costs were equivalent. Older adults showed large practice effects on switch trials. Third, age-equivalent switch costs were maintained across a two month retention period. Finally, the main constraint on whether age equivalence was observed in task switching performance was memory load. Older adults were unable to capitalize on practice under high memory loads. These data are discussed in terms of their implications for both general and process specific cognitive aging models.