工作记忆和感觉运动速度在心算加工年老化过程中的作用

对心算加工年老化研究有助于阐明认知老化规律,然而有关心算老化的少量研究结果仍存在不一致甚至矛盾之处。导致这种不一致的原因十分复杂,表面上看,不同认知老化研究所采用的统计方法不尽相同导致了结果的歧异。例如,在心算的年老化研究中,有的研究结论基于群体的数据分析,如层级回归分析(hierarchical regres-sion analyses)或方差分析,如Sahhouse和Coon(1994);另有一些研究先对每一个体数据作线性回归分析,如此得到斜率和截距(分别表示心算的中枢加工时间和外周感觉运动时间),然后再行层级回归分析或方差分析,如Al-len等(1992,1997)。这两类统计分析所得的结果很不一致。从理论上看,只要所采用的统计方法是合理的,统计方法的不尽相同应不会导致矛盾。但在实际情况下,统计分析误差增加了结论不一致的可能性,从而增大了揭示心算老化复杂性规律的难度。事实上,心算活动的年龄差异可能来自于记忆、加工速度等不同认知资源的老化差异。为了深入探讨这一问题,我们进一步研究了工作记忆和感觉运动速度在心算加工年老化过程中的作用。被试共161人,20—79岁,身体健康,受教育年限12年以上,以10岁段划分为6个年龄组,组间文化程度基本匹配。被试任务包括：(1)连续减法心算,分别为1000—3、1000—7、1000—13及1000—17等4种,在排除了被试看屏幕和按键的感觉运动时间后得到心算所需的时间;(2)数字计算工作记忆,根据工作记忆对信息同时进行加工和储存的特点,要求被试计算完题后再回忆答案,以获得工作记忆广度指标;(3)“数字复制”(digit copying),以获得感觉运动速度指标。实验在386微机上进行。对所得数据分别进行了上述群体数据与个体数据分析。两种数据分析方法得到了相同的结果,一致表明,在控制工作记忆与感觉运动速度的年龄差异后,心算活动的年龄差异显著降低。而且,控制感觉运动速度的年龄差异后心算活动年龄差异的降低程度要大于控制工作记忆的年龄差异后心算活动年龄差异的降低程度。这说明,感觉运动速度在心算加工年老化过程中发挥了更大作用。但是,工作记忆与感觉运动速度二者的年龄差异并不能完全解释心算活动的年龄差异,表明心算加工的年老化存在其特殊性过程,不支持认知老化的普遍减慢假说(genenalized slowing hypotllesis)。     

Dissociating retention and access in working memory: an age-comparative study of mental arithmetic

In two experiments, young and older adults solved arithmetic chain tasks with single-digit operands, with or without a concurrent memory load of three or six digits. Variables in the arithmetic tasks had to be replaced by digits from the screen or from the memory set. A task-irrelevant concurrent load impaired neither speed nor accuracy of arithmetic in younger adults. In Experiment 2, this was also true for older adults. A large decrease in arithmetic performance was observed, however, when variables in the arithmetic task had to be substituted by digits from the memory list. Older adults had specific problems with this condition in Experiment 1, where the substitution involved two successive steps, but not in Experiment 2, where the substitution from memory could be done in a single step. The results are difficult to reconcile with models assuming a common resource for storage and processing. Rather, they are compatible with the hypothesis that a concurrent memory load interferes with a processing task only during the points of access to working memory. Further, even though access to working memory was found to be the critical source of concurrent-load interference, it was found to be insensitive to the effects of adult aging.     

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.     

Contents Index Volume 8

In a group of 62 young and 75 older subjects, LISREL models were used to predict ordered list recall from age category, self-reported strategy use and selected cognitive abilities. It was found that: (a) age differences in the strategies of associating and repetition/testing were completely explained by speed of mental processing and associative memory; (b) only these two age-related strategies were efficacious strategies, the one not age-related strategy (concentrating) was not; (c) a large proportion of the age-related variance in list recall performance was mediated by speed and associative memory; and (d) this influence of speed and associative memory on ordered list recall was partly mediated by strategies. These results support a moderate version of the production deficiency explanation of memory aging, in which age differences in efficacious strategy use are explained by age differences in basic cognitive abilities.     

Explaining age differences in temporal working memory

To determine the cognitive mechanisms underlying age differences in temporal working memory (WM), the authors examined the contributions of item memory, associative memory, simple order memory, and multiple item memory, using parallel versions of the delayed-matching-to-sample task. Older adults performed more poorly than younger adults on tests of temporal memory, but there were no age differences in nonassociative item memory, regardless of the amount of information to be learned. In contrast, a combination of associative and simple order memory, both of which were reduced in older adults, completely accounted for age-related declines in temporal memory. The authors conclude that 2 mechanisms may underlie age differences in temporal WM, namely, a generalized decline in associative ability and a specific difficulty with order information.     

Age and skilled performance: contributions of working memory and processing speed

In this study, we examined the interrelationships among age, working memory (WM), processing speed, and the development of skilled performance. Younger (M=20.5) and older (M=68.9) adults were trained on an alphabet arithmetic task (Haider & Frensch, 1996) administered across three consecutive days. Although older adults were slower than younger adults, both age groups' response latencies decreased as a result of practice. Contrary to expectations, WM and processing speed were significantly correlated with performance late in training. Partial correlations suggested that age differences in performance at the end of training were mediated by individual differences in cognitive processing speed.     

Differential effects of age on item and associative measures of memory: a meta-analysis

In this meta-analysis, the authors evaluated recent suggestions that older adults' episodic memory impairments are partially due to a reduced ability to encode and retrieve associated/bound units of information. Results of 90 studies of episodic memory for both item and associative information in 3,197 young and 3,192 older adults provided support for the age-related associative/binding deficit suggestion, indicating a larger effect of age on memory for associative information than for item information. Moderators assessed included the type of associations, encoding instructions, materials, and test format. Results indicated an age-related associative deficit in memory for source, context, temporal order, spatial location, and item pairings, in both verbal and nonverbal material. An age-related associative deficit was quite pronounced under intentional learning instructions but was not clearly evident under incidental learning instructions. Finally, test format was also found to moderate the associative deficit, with older adults showing an associative/binding deficit when item memory was evaluated via recognition tests but not when item memory was evaluated via recall tests, in which case the age-related deficits were similar for item and associative information.     

Working memory and arithmetic calculation in children: the contributory roles of processing speed, short-term memory, and reading

The cognitive underpinnings of arithmetic calculation in children are noted to involve working memory; however, cognitive processes related to arithmetic calculation and working memory suggest that this relationship is more complex than stated previously. The purpose of this investigation was to examine the relative contributions of processing speed, short-term memory, working memory, and reading to arithmetic calculation in children. Results suggested four important findings. First, processing speed emerged as a significant contributor of arithmetic calculation only in relation to age-related differences in the general sample. Second, processing speed and short-term memory did not eliminate the contribution of working memory to arithmetic calculation. Third, individual working memory components--verbal working memory and visual-spatial working memory--each contributed unique variance to arithmetic calculation in the presence of all other variables. Fourth, a full model indicated that chronological age remained a significant contributor to arithmetic calculation in the presence of significant contributions from all other variables. Results are discussed in terms of directions for future research on working memory in arithmetic calculation.     

Age-related differences in associative memory depend on the types of associations that are formed

Building on well-established findings of age-related decline in associative memory, we examined whether the magnitude of age differences depends on the types of associations that are formed. Specifically, because of predominant age-related changes in the hippocampus, we expected to find larger age differences in recognition of between-domain than within-domain associations. Twenty younger and 20 older healthy adults were given two associative recognition tests, using face-name and word-word pairs, that were matched for difficulty level. As hypothesized, a three-way interaction indicated that, relative to item recognition, age differences in associative recognition were greater for between-domain face-name associations than for within-domain word-word associations. This dissociation is consistent with the idea that the hippocampus plays a prominent role in binding information received from distal neocortical regions. The discussion focuses on the roles of recollection and familiarity in supporting associative memory as well as implications for the remediation of age-related memory decline.     

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.     

Cognitive Mechanisms Underlying Decrements in Mental Synthesis in Older Adults

The extent and nature of age-related differences in mental synthesis was examined in light of Baddeley's working memory model and resource theories. Mental synthesis performance of 30 young, young-old, middle-old and old-old adults was examined using a dual-task experiment and individual differences approach. Age-related differences in mental synthesis were shown, with an unprecedented heightened decrement evident after the age of 85. The central executive was not a mechanism of this decline. Executive function, speed of information processing, and working memory capacity were mechanisms underlying this decline, and together accounted for 86% of the age-related variance in mental synthesis. Environmental support enhanced mental synthesis.     

Age-related differences in the course of cognitive skill acquisition: the role of regional cortical shrinkage and cognitive resources

This study examined the impact of age-related differences in regional cerebral volumes and cognitive resources on acquisition of a cognitive skill. Volumes of brain regions were measured on magnetic resonance images of healthy adults (aged 22-80). At the early stage of learning to solve the Tower of Hanoi puzzle, speed and efficiency were associated with age, prefrontal cortex volume, and working memory. A similar pattern of brain-behavior associations was observed with perseveration measured on the Wisconsin Card Sorting Test. None of the examined structural brain variables were important at the later stages of skill acquisition. When hypertensive participants were excluded, the effect of prefrontal shrinkage on executive aspects of performance was no longer significant, but the effect of working memory remained.     

Age differences in working memory— The roles of storage and selective access

Twenty-four young (23 years) and 24 old (71 years) adults performed arithmetic tasks with working memory loads ranging from 1 to 4. Age groups were equivalent in mean accuracy and speed of arithmetic operations under minimal working memory load, but old adults were slower than young with memory demands >1. Access to a new object in working memory as the basis of computation required additional time. This object-switching cost increased with increases in memory demand, but was unaffected by age, indicating that old adults have no deficit in selective access to working memory.     

Patterns and Predictors of Adult Age Differences in Mental Imagery

Adult age differences in, and predictors of, component imagery processes were examined across a broad elderly adult age range (65-86 years). Relative to younger adults, older adults were slower and less accurate on tasks of image generation, maintenance, scanning, and rotation. Ability to maintain mental images in particular was compromised by older age. Manipulations of stimulus complexity produced inconsistent differential age effects across tasks. Processing speed and sensorimotor functioning were prominent predictors of performance and age-related variance in all imagery components, with smaller contributions from working memory and executive function. These findings suggest that age-related decrements in individual imagery processes depend primarily on how quickly information can be processed and on the neurophysiological integrity of the ageing brain.     

Working-memory mediationof adult age differences in integrativereasoning

Three research methods were used to investigate the hypothesized mediational influence of working memory on age-related differences in integrative reasoning. Results from all three procedures were consistent with the hypothesis because (1) statistical control of an index of working memory attenuated the age differences in reasoning accuracy, (2) young adults were more accurate than older adults in a measure reflecting the preservation of information during processing, and (3) young adults performing the task with a concurrent memory load exhibited a qualitative pattern of performance similar to that of older adults performing the task without a concurrent memory load.     

An individual differences analysis of ability and strategy influences: age-related differences in associative learning

The relationships among abilities, strategies, and performance on an associative learning task were investigated for young (aged 17 to 34) and older adults (aged 60 to 82). Participants received extensive practice on a noun-pair task in which they could use a visual-scanning strategy or a memory-retrieval strategy. Older adults were more likely to use the scanning strategy. Age differences were reduced when comparisons were made only for participants using a retrieval strategy. Associative memory was predictive of learning on the task, and semantic memory access speed was predictive of practiced performance. Practiced performance on a memory-search task that also required associative learning was predictive of practiced noun-pair performance. Models of ability-performance relationships for skill acquisition are discussed.     

Age-related differences in associative memory depend on the types of associations that are formed

ABSTRACT

Building on well-established findings of age-related decline in associative memory, we examined whether the magnitude of age differences depends on the types of associations that are formed. Specifically, because of predominant age-related changes in the hippocampus, we expected to find larger age differences in recognition of between-domain than within-domain associations. Twenty younger and 20 older healthy adults were given two associative recognition tests, using face–name and word–word pairs, that were matched for difficulty level. As hypothesized, a three-way interaction indicated that, relative to item recognition, age differences in associative recognition were greater for between-domain face–name associations than for within-domain word–word associations. This dissociation is consistent with the idea that the hippocampus plays a prominent role in binding information received from distal neocortical regions. The discussion focuses on the roles of recollection and familiarity in supporting associative memory as well as implications for the remediation of age-related memory decline.     

Cognitive skill learning: age-related differences in strategy shifts and speed of component operations

Younger and older adults solved novel arithmetic problems and reported the strategies used for obtaining solutions. Age deficits were demonstrated in the latencies for computing and retrieving solutions and in the shift from computation to retrieval. Rates of improvement within age groups were parallel for computations and retrievals, suggesting a single, age-attenuated mechanism that affects practice-related speedup. The age-related delay in strategy shift suggests either reluctance to use retrieval or an associative memory deficit. Experiment 1 showed that skill acquisition was unaffected by the presence and frequency of postresponse strategy probes for both age groups. Experiment 2 showed that pretraining item-learning operations facilitated subsequent item learning and that pretraining either item-learning operations or the algorithm did not alter the age trends.     

Age-related differences in inference revision processing

In comparison to younger adults, older adults demonstrate deficiencies in cognitive and linguistic abilities. Such cognitive factors that decline with age include working memory capacity and inhibitory abilities. The purpose of the present investigation was to measure differences in time course processing of inference revision abilities, as well as working memory, as they exist relative to adult age differences. Fifteen neurologically intact older adults and 15 younger adults participated in this study. A cross-modal lexical priming paradigm was chosen as the measure of the inference revision task; the listening span task of Tompkins, Bloise, Timko, and Baumgaertner (1994) was selected as the measure of working memory. Both groups demonstrated normal priming effects. No age-related differences were found on the working memory measure. Age-related differences did emerge on inferencing abilities. A significant correlation emerged between the older group's performance on comprehending inference revisions and their working memory capacity. Generally, inhibitory abilities and working memory capacity appeared to adversely affect older participant's performance.     

Using eye movement measures to investigate effects of age on memory for objects in a scene

We examined whether there were age-related differences in eye movements during intentional encoding of a photographed scene that might account for age-related differences in memory of objects in the scene. Younger and older adults exhibited similar scan path patterns, and visited each region of interest in the scene with similar frequency and duration. Despite the similarity in viewing, there were fundamental differences in the viewing-memory relationship. Although overall recognition was poorer in the older than younger adults, there was no age effect on recognition probability for objects visited only once. More importantly, re-visits to objects brought gain in recognition probability for the younger adults, but not for the older adults. These results suggest that the age-related differences in object recognition performance are in part due to inefficient integration of information from working memory to longer-term memory.