Age and working memory: The role of perceptual speed, the central executive, and the phonological loop.

In a study (N?=?61) comparing older (age range?=?60–80 years, M?=?67) and younger (age range?=?20-33 years, M?=?25) people, age deficits were observed in working memory, perceptual speed, and central executive functioning but not in phonological loop functioning. Controlling for age differences in central executive performance removed over 50% of the age-related variance in working memory span. However, controlling for perceptual speed removed all of the age-related variance in working memory span. In addition, age differences in central executive functioning were largely eliminated after controlling for age deficits in perceptual speed. These findings suggest that age differences in central executive functioning are primarily attributable to a general slowdown in the rate at which information is activated within the working memory system and that no specific deficits in the central executive occur as a consequence of aging. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Cognitive mediation of adult age differences in language performance.

Young (M?=?20 years) and old (M?=?68 years) adults completed language processing tasks, measures of working memory capacity (backward span and the n-back lag task), inhibitory efficiency (Stroop interference), and processing speed (color naming). Regression analyses revealed that each of the resource measures significantly predicted language performance and attenuated variance in language performance that would otherwise be attributed to age. When speed variance was entered into the equation first, the mediating influence of the inhibition and working memory measures remained significant. When speed and inhibition differences were controlled, the working memory measures could not reliably predict language performance. These results suggest that language performance differences may be fundamentally mediated by age differences in processing speed and inhibitory efficiency. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Meta-analyses of age–cognition relations in adulthood: Estimates of linear and nonlinear age effects and structural models.

A meta-analysis was conducted on 91 studies to derive a correlation matrix for adult age, speed of processing, primary–working memory, episodic memory, reasoning, and spatial ability. Structural equation modeling with a single latent common cognitive factor showed that all cognitive measures shared substantial portions of age-related variance. A mediational model revealed that speed of processing and primary–working memory appear to be important mediators of age-related differences in the other measures. However, not all of the age-related influences were mediated. An examination of quadratic age effects and correlational patterns for subsamples under and over 50 years of age revealed that (a) negative age–cognition relations were significant for the 18- to 50-year-old sample and (b) the age-related decline accelerated significantly over the adult life span for variables assessing speed, reasoning, and episodic memory. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Mapping the Developmental Constraints on Working Memory Span Performance.

This study investigated the constraints underlying developmental improvements in complex working memory span performance among 120 children of between 6 and 10 years of age. Independent measures of processing efficiency, storage capacity, rehearsal speed, and basic speed of processing were assessed to determine their contribution to age-related variance in complex span. Results showed that developmental improvements in complex span were driven by 2 age-related but separable factors: 1 associated with general speed of processing and 1 associated with storage ability. In addition, there was an age-related contribution shared between working memory, processing speed, and storage ability that was important for higher level cognition. These results pose a challenge for models of complex span performance that emphasize the importance of processing speed alone. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Adult age differences in long-term memory for performed activities

Participants in two studies conducted by Salthouse (in press) were called 2 to 182 days after participation and asked to describe the activities that they had performed in the previous study. Hierarchical regression analyses were used to examine the prediction of activity recall from age, speed, and retention interval. Overall, age was associated with 20% of the variance in activity recall, and retention interval was associated with 19%, but there was no significant interaction of age and retention interval. When perceptual speed was entered into the regression equation before age, the age-related variance was reduced by 70%. A small, but statistically significant, amount of age-related variance in activity memory remained after controlling for speed and retention interval.     

The role of processing resources in age-related prospective and retrospective memory within old age.

This study investigated the role of processing speed and working memory in prospective and retrospective memory (i.e., free recall) performance within old age. The aim was to examine age-related differences in both memory domains within the age range of 65 to 80 years. The sample consisted of 361 older adults from Wave 1 data of the Zurich Longitudinal Study on Cognitive Aging. Using structural equation modeling, prospective memory, free recall, working memory, and processing speed were identified as latent constructs. Age effects were found to be larger for prospective memory than for free recall. Furthermore, when controlling for individual differences in working memory and processing speed, unique age effects remained for prospective, but not retrospective, memory performance. Results indicate that, within old age, prospective memory represents a distinct memory construct that is partially independent of age-related individual differences in speed of processing, working memory, and retrospective memory. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Adult age differences in temporal and item memory.

Three experiments tested whether the relationship between age differences in temporal and item memory depends on the degree to which the item memory measure relies on memory for context. The authors predicted a stronger relationship of temporal memory to free recall than to recognition memory. Results showed that age differences in temporal memory could be eliminated after controlling for free recall but not recognition memory performance. Under some conditions recognition memory accounted for a significant portion of age-related variance in temporal memory. These results challenge past research that has interpreted age differences in temporal and item memory as independent and suggest that a generalized decline in context memory may underlie reduced performance in older adults on all types of memory tests. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Age-Related Differences in Performance on the Wisconsin Card Sorting Test: A Meta-Analytic Review.

Two meta-analyses investigating age-related differences in performance on a popular measure of executive function, the Wisconsin Card Sorting Test (WCST), are reported. The 1st meta-analysis examined age-related changes in performance for the number of categories achieved, and the 2nd meta-analysis examined performance for the number of perseverative errors committed. Results indicated that robust age differences were present on both measures. Further analysis of moderator variables revealed reliable effects of education and test version on both measures, whereas test modality led to marginally significant differences in effect sizes obtained only for the number of categories achieved. Findings are discussed along with current accounts of age differences in performance of the WCST. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Shared age-related influences on cognitive and noncognitive variables

Analyses of new data and of previously published data were conducted to examine the degree to which age-related variance was shared across cognitive and noncognitive variables and to investigate possible alterations in the composition of a factor common to all variables as a function of age. The results indicated that measures of visual acuity, grip strength, and blood pressure shared age-related variance with measures of perceptual speed, episodic memory, spatial visualization, and inductive reasoning. However, although the cognitive variables shared similar amounts of variance in age-restricted and age-partialed analyses, the variance shared between cognitive and noncognitive variables was substantially reduced after controlling the influence of age.     

Predicting episodic memory performance of very old men and women: Contributions from age, depression, activity, cognitive ability, and speed.

Regression models were developed to explain age-related and total variance in memory and to determine the independent contribution from general processing speed, having taken into account cognitive and noncognitive individual differences. Episodic memory was assessed for 3 tasks in a population-based sample of 951 adults comprising 515 men and 436 women (aged 70–96, M?=?77.6, SD?=?5.5). Correlations between age and memory accounted for 6%–9% of the variance. Hierarchical multiple regressions showed a reduction in this age-related variance by up to 94%, after entering gender, depression, health, cognitive status, activities, and speed. General processing speed was the major mediator of age-related variance in memory. Although both the age-related variance and the speed-related variance in memory were significantly reduced by prior entry of other individual differences variables for all 3 tasks, speed remained a significant mediator of remembering, and negligible differences in the residual age-related variance were observed by inclusion of other background variables. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

Mediators of long-term memory performance across the life span.

An individual-differences approach was used to examine the component processes that predict episodic long-term memory performance. A total of 301 participants ages 20-90 received a 7-hr cognitive battery across 3 days. Key constructs hypothesized to affect long-term memory function were assessed, including multiple measures of working memory and perceptual speed. Latent-construct, structural equation modeling was used to examine the relationship of these measures and age to different types of long-term memory tasks. Speed was a key construct for all 3 types of memory tasks, mediating substantial age-related variance; working memory was a fundamental construct for free and cued recall but not spatial memory. The data suggest that both speed and working memory are fundamental to explaining age-related changes in cognitive aging but that the relative contributions of these constructs vary as a function of the type of memory task. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Neuroanatomical and cognitive mediators of age-related differences in episodic memory.

Aging is associated with declines in episodic memory. In this study, the authors used a path analysis framework to explore the mediating role of differences in brain structure, executive functions, and processing speed in age-related differences in episodic memory. Measures of regional brain volume (prefrontal gray and white matter, caudate, hippocampus, visual cortex), executive functions (working memory, inhibitory control, task switching, temporal processing), processing speed, and episodic memory were obtained in a sample of young and older adults. As expected, age was linked to reduction in regional brain volumes and cognitive performance. Moreover, neural and cognitive factors completely mediated age differences in episodic memory. Whereas hippocampal shrinkage directly affected episodic memory, prefrontal volumetric reductions influenced episodic memory via limitations in working memory and inhibitory control. Age-related slowing predicted reduced efficiency in temporal processing, working memory, and inhibitory control. Lastly, poorer temporal processing directly affected episodic memory. No direct effects of age on episodic memory remained once these factors were taken into account. These analyses highlight the value of a multivariate approach with the understanding of complex relationships in cognitive and brain aging. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Measures of fluency as predictors of incidental memory among older adults.

This study investigated fluency performance as a mediator of age-related declines in incidental memory performance as both are thought to rely on strategic retrieval processes. A large sample of community dwelling older adults completed a battery of tests assessing fluency, verbal knowledge, speed of information processing, and incidental recall. Fluency measures included initial and excluded letter fluency and the Uses for Objects Test, and they were assumed to reflect increasing reliance on strategic retrieval search. Speed emerged as the best mediator of age-related variance in incidental recall, and Uses for Objects Test performance added to the variance after controlling for verbal knowledge and speed. The results suggest that age-related decline in incidental recall is largely due to speed and the strategic search of memory. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Working memory and bias in reasoning across the life span.

Age differences in syllogistic reasoning in relation to crystallized and fluid ability were studied in 278 adults from 19 to 96 yrs of age. Two reasoning tasks, the evaluation and the construction of conclusions for syllogisms of varying complexity and believability, a vocabulary test, and 3 tasks of working memory were administered. The magnitude of age-related variance on selected reasoning tasks was only partially reduced by statistically controlling measures of both working memory and vocabulary. Additional age-related effects on reasoning were found to be significantly associated with number of mental models and bias produced by conflict between belief and logic. A significant bias was also found toward acceptance of invalid syllogisms as valid, even when contents were abstract. These sources of error in logic are discussed in relation to P. N. Johnson-Laird's (1983) theory of mental models and J. St. B. T. Evans's (1989) account of bias in human reasoning. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Does differential strategy use account for age-related deficits in working-memory performance?

The strategy-deficit hypothesis states that age differences in the use of effective strategies contribute to age-related deficits in working memory span performance. To evaluate this hypothesis, strategy use was measured with set-by-set strategy reports during the Reading Span task (Experiments 1 and 2) and the Operation Span task (Experiment 2). Individual differences in the reported use of effective strategies accounted for substantial variance in span performance. In contrast to the strategy-deficit hypothesis, however, young and older adults reported using the same proportion of normatively effective strategies on both span tasks. Measures of processing speed accounted for a substantial proportion of the age-related variance in span performance. Thus, although use of normatively effective strategies accounts for individual differences in span performance, age differences in effective strategy use cannot explain the age-related variance in that performance. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The effects of age, illustrations, and task variables on the performance of procedural assembly tasks.

Older adults may be disadvantaged in the performance of procedural assembly tasks because of age-related declines in working memory operations. It was hypothesized that adding illustrations to instructional text may lessen age-related performance differences by minimizing processing demands on working memory in the elderly. In the present study, younger and older adults constructed a series of 3-dimensional objects from 3 types of instructions (text only, illustration only, or text and illustrations). Results indicated that instructions consisting of text and illustrations reduced errors in construction for both age groups compared with the other formats. Younger adults, however, outperformed older adults under all instructional format conditions. Measures of spatial and verbal working memory and text comprehension ability accounted for substantial age-related variance across the different format conditions but did not fully account for the age differences observed. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

Memory for news in young and old adults.

Memory for news stories was studied in 48 young and 48 old adults (20–40 and 60–80 years of age, respectively). Three stories selected from actual news programs were presented in print, audio, and TV formats for study. Young adults recalled a higher proportion of news content than old adults and performed better on source recognition tests. Presentation of the information in a TV format led to better performance than in an audio format for both young and old adults. Hierarchical regression analysis revealed that approximately 86% of the age-related variance in news recall was mediated by measures of sensory acuity and processing speed, and commonality analysis revealed that 75% of the age-related variance was mediated jointly by acuity and speed. Findings support common-cause and generalized slowing views of memory impairment in old age. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Differential age-related processing limitations in recall and recognition tasks.

The degree to which processing resources are responsible for age differences in performance on recall and recognition tasks was examined in this study. To examine this, a secondary task incorporating a memory component (digit preloads) was implemented during retrieval. Results revealed that older adults, relative to younger adults, exhibited greater decrements in secondary task performance as the difficulty of the secondary task increased. These age differences were greater in the recall task than in the recognition task. Hierarchical regression analyses indicated that speed accounted for the largest proportion of age-related variance in the recall task while both speed and working memory contributed to much of the secondary task variance. Results confirm the hypothesis that recall requires greater processing capacity than recognition and that older adults have greater processing-capacity limitations than younger adults. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

Speed and intelligence in old age.

Past research suggests that age differences in measures of cognitive speed contribute to differences in intellectual functioning between young and old adults. To investigate whether speed also predicts age-related differences in intellectual performance beyond age 70 yrs, tests indicating 5 intellectual abilities (speed, reasoning, memory, knowledge, and fluency) were administered to a close-to-representative, age-stratified sample of old and very old adults. Age trends of all 5 abilities were well described by a negative linear function. The speed-mediated effect of age fully explained the relationship between age and both the common and the specific variance of the other 4 abilities. Results offer strong support for the speed hypothesis of old age cognitive decline but need to be qualified by further research on the reasons underlying age differences in measures of speed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Analysis of adult differences on the Raven's Advanced Progressive Matrices Test.

Examined the nature of performance, and specifically, age-related performance, on the Raven's Advanced Progressive Matrices (APM) Test. In the 1st of 2 studies, 2 tests presumed to measure each of 4 hypothesized components of the APM and 3 tests presumed to measure processing speed were presented to 165 young adults. On the basis of correlational and confirmatory analyses, 1 of the components was not included in Study 2. The 2nd study was designed to examine the influence of the 3 remaining components, processing speed, and working memory on the individual and age-related differences on the APM. Participants included 183 adults aged 21–83 yrs. The results suggest that although all 3 components are important to performance on the APM, rule application tasks seem to hold the most promise in accounting for age-related variance on the APM. (PsycINFO Database Record (c) 2010 APA, all rights reserved)