Do working-memory executive components mediate the effects of age on strategy selection or on strategy execution? Insights from arithmetic problem solving

Younger and older adults performed an inequality verification task (7+6 < 15, Yes/No?) in a control condition and in a dual-task condition where they simultaneously performed an executive-component task. Arithmetic-problem characteristics were manipulated in order to test strategy selection (i.e., choice of appropriate strategies in order to improve performance) and strategy execution (i.e., performance of the cognitive processes involved in each strategy). Results revealed that strategy selection changes with age: Older adults mainly selected one type of strategies in contrast to younger adults who used several types of strategies. These age-related changes were similar in the control and dual-task conditions. Strategy execution also changed with age, as shown by larger age-related differences on hardest problems. These age-related changes were larger in the dual-task condition, compared to the control condition. This impact of executive components as mediator of age-related changes depended on general age-related slowing. We discuss these findings in order to further understand the effects of age on arithmetic performance.     

Alzheimer's disease disrupts arithmetic fact retrieval processes but not arithmetic strategy selection

Three groups of healthy younger adults, healthy older adults, and probable AD patients, performed an addition/number comparison task. They compared 128 couples of additions and numbers (e.g., 4 + 9 15) and had to identify the largest item for each problem by pressing one of two buttons located under each item. Manipulations of problem characteristics (i.e., problem difficulty and splits between correct sums and proposed numbers) enabled us to examine strategy selection and specific arithmetic fact retrieval processes. Results showed that arithmetic facts retrieval processes, which were spared with aging, were impaired in AD patients. However, AD patients were able to switch between strategies across trials according to problem characteristics as well as healthy older adults, and less systematically than healthy younger adults. We discuss implications of these findings for further understanding AD-related differences in arithmetic in particular, and problem solving in general.     

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.     

Age- and practice-related influences on dual-task costs and compensation mechanisms under optimal conditions of dual-task performance

Impaired dual-task performance in younger and older adults can be improved with practice. Optimal conditions even allow for a (near) elimination of this impairment in younger adults. However, practice effects under these conditions in older adults are unknown. Further, it is open, how changed task scheduling and/ or the acquisition of task coordination skills affect the temporal overlap of two tasks in different age groups; this overlap indicate the involvement of these practice-related mechanisms to compensate for impaired dual-task performance. In a dual-task situation of Schumacher et al. (2001 , Psychological Science, 12, 230) including optimal conditions for dual-task performance, both younger and older adults were able to achieve an improvement in dual-task performance with 8 practice sessions to the same degree. The temporal task overlap changed similarly in both age groups during these sessions demonstrating a similar degree of the involvement of compensation mechanisms in younger and older adults. At the end of practice, however, we showed that older adults do not achieve the same optimized dual-task performance level of younger adults.     

Dual-task costs of texting while walking forward and backward are greater for older adults than younger adults

Cognitive-motor dual-tasking involves concurrent performance of two tasks with distinct cognitive and motor demands and is associated with increased fall risk. In this hypothesis-driven study, younger (18–30 years, n = 24) and older (60–75 years, n = 26) adults completed six walking tasks in triplicate. Participants walked forward and backward along a GAITRite mat, in isolation or while performing a verbal fluency task. Verbal fluency tasks involved verbally listing or typing on a smartphone as many words as possible within a given category (e.g., clothes). Using repeated measures MANOVA models, we examined how age, method of fluency task (verbal or texting), and direction of walking altered dual-task performance. Given that tasks like texting and backward walking require greater cognitive resources than verbal and forward walking tasks, respectively, we hypothesized older adults would show higher dual-task costs (DTCs) than younger adults across different task types and walking directions, with degree of impairment more apparent in texting dual-task trials compared to verbal dual-task trials. We also hypothesized that both age groups would have greater DTCs while walking backward than while walking forward, regardless of task.Independent of age group, velocity and stride length were reduced for texting compared to the verbal task during both forward and backward walking; cadence and velocity were reduced while walking forward compared to walking backward for the texting task; and stride length was reduced for forward walking compared to backward walking during the verbal task. Younger adults performed better than older adults on all tasks with the most pronounced differences seen in velocity and stride length during forward-texting and backward-texting. Interaction effects for velocity and stride length while walking forward indicated younger adults performed better than older adults for the texting task but similarly during the verbal task. An interaction for cadence during the verbal task indicated younger adults performed better than older adults while walking backward but similarly while walking forward.In summary, older adults experienced greater gait decrement for all dual-task conditions. The greater declines in velocity and stride length in combination with cadence being stable suggest reductions in velocity during texting were due to shorter strides rather than a reduced rate of stepping. Contrary to our hypotheses, we found greater DTCs while walking forward rather than backward, which may be due to reduced gait performance during single-task backward walking; thus, further decrements with dual-tasking are unlikely. These findings underscore the need for further research investigating fall risk potential associated with texting and walking among aging populations and how interventions targeting stride length during dual-task circumstances may improve performance.     

Heuristics versus direct calculation,and age-related differences in multiplication: an evidence accumulation account of plausibility decisions in arithmetic

We offer a new theoretical angle for cognitive arithmetic, which is that evidence accumulation may play a role in problem plausibility decisions. We build upon previous studies that have considered such a hypothesis, and here formally evaluate the paradigm. We develop the finding that performance differences, due to variations in strategy use and aging effects, can indeed be reasonably explained through these accumulation-to-bound cognitive models. Results suggest that these models may be effectively used to learn more about the underlying cognitive processes. In this study, we modelled young (18–24) and older (68–82) adults’ solution times in performing arithmetic verification (e.g. whether 8?×?5?=?41 is true/false). The domain-relevant factors in strategy use (problem-verification heuristics) and aging differences (older/younger adult groups) were analyzed by a response process model of the latency data, that is fit by participant and item. Lower thresholds accounted for the faster response times (RTs) for problems solved with heuristics (arithmetic rule-violation checking strategies), as opposed to problems solved by calculation approaches. A more rapid accumulation accounted for faster RTs on problems in which two arithmetic rules were violated (strategy combination) rather than one. Third, higher thresholds (i.e. preferring to have greater certainty before responding) accounted for older adults’ slower speed. These findings are in support of accumulation models being relevant for more complex cognitive tasks, as well as to account for the age-related differences therein.     

On mental multiplication and age.

In 2 experiments, younger and older adults were presented with simple multiplication problems (e.g., 4 x 7 = 28 and 5 x 3 = 10) for their timed, true or false judgments. All of the effects typically obtained in basic research on mental arithmetic were obtained, that is, reaction time (a) increased with the size of the problem, (b) was slowed for answers deviating only a small amount from the correct value, and (c) was slowed when related (e.g., 7 x 4 = 21) versus unrelated (e.g., 7 x 4 = 18) answers were presented. Older adults were slower in their judgments. Most important, age did not interact significantly with problem size or split size. The authors suggest that elderly adults' central processes, such as memory retrieval and decision making, did not demonstrate the typical age deficit because of the skilled nature of these processes in simple arithmetic.     

Domain-general contributions to social reasoning: theory of mind and deontic reasoning re-explored

Using older adults and dual-task interference, we examined performance on two social reasoning tasks: theory of mind (ToM) tasks and versions of the deontic selection task involving social contracts and hazardous conditions. In line with performance accounts of social reasoning, evidence from both aging and the dual-task method suggested that domain-general resources contribute to performance of these tasks. Specifically, older adults were impaired relative to younger adults on all types of social reasoning tasks tested; performance varied as a function of the demands these tasks placed on domain-general resources. Moreover, in younger adults, simultaneous performance of a working memory task interfered with younger adults' performance on both types of social reasoning tasks; here too, the magnitude of the interference effect varied with the processing demands of each task. Limits placed on social reasoning by executive functions contribute a great deal to performance, even in old age and in healthy younger adults under conditions of divided attention. The role of potentially non-modular and modular contributions to social reasoning is discussed.     

Simple addition and multiplication: No comparison

Some models of memory for arithmetic facts (e.g., 5+2=7, 6×7=42) assume that only the max-left order is stored in memory (e.g., 5+2=7 is stored but not 2+5=7). These models further assume an initial comparison of the two operands so that either operand order (5+2 or 2+5) can be mapped to the common internal representation. We sought evidence of number comparison in simple addition and multiplication by manipulating size congruity. In number comparison tasks, performance costs occur when the physical and numerical size of numerals are incongruent (8 3) relative to when they are congruent (8 3). Sixty-four volunteers completed a number comparison task, an addition task, and a multiplication task with both size congruent and size incongruent stimuli. The comparison task demonstrated that our stimuli were capable of producing robust size congruity and split effects. In the addition and multiplication task, however, we were unable to detect any of the RT signatures of comparison or reordering processes despite ample statistical power: Specifically, there was no evidence of size congruity, split, or order effects in either the addition or multiplication data. We conclude that our participants did not routinely engage a comparison operation and did not consistently reorder the operands to a preferred orientation.     

An examination of age-related changes in the control of lexical and sublexical pathways in mapping spelling to sound

The current study investigated the extent to which young and older adults are able to direct attention to distinct processes in mapping spelling onto sound. Young and older adults completed either a speeded pronunciation task (reading aloud words) or regularization task (pronouncing words based on spelling-to-sound correspondences, e.g., pronouncing PINT such that it rhymes with HINT) in order to bias processing of lexical, whole-word information, or sublexical, spelling-to-sound mapping, respectively. Both younger and older adults produced reduced word-frequency effects and lexicality effects in the regularization task compared to the normal pronunciation task. Importantly, compared to younger adults, older adults produced exaggerated effects of task (i.e., pronunciation vs. regularization) on the observed frequency and lexicality effects. These results highlight both the flexibility of the lexical processing system and changes in the influence of the underlying lexical route due to additional 50 years of reading experience and/or changes in attentional control.     

Preferences for emotional information in older and younger adults: a meta-analysis of memory and attention tasks

The authors conducted a meta-analysis to determine the magnitude of older and younger adults' preferences for emotional stimuli in studies of attention and memory. Analyses involved 1,085 older adults from 37 independent samples and 3,150 younger adults from 86 independent samples. Both age groups exhibited small to medium emotion salience effects (i.e., preference for emotionally valenced stimuli over neutral stimuli) as well as positivity preferences (i.e., preference for positively valenced stimuli over neutral stimuli) and negativity preferences (i.e., preference for negatively valenced stimuli to neutral stimuli). There were few age differences overall. Type of measurement appeared to influence the magnitude of effects; recognition studies indicated significant age effects, where older adults showed smaller effects for emotion salience and negativity preferences than younger adults.     

Effects of associative learning on age differences in task-set switching

Costs of switching between tasks may disappear when subjects are able to learn associations between tasks, stimuli, and responses (cf. Rogers, R. D., & Monsell, S. (1995). Costs of a predictable switch between simple cognitive tasks. Journal of Experimental Psychology: General, 124, 207-231). The first aim of this study was to examine this possibility by manipulating stimulus-set size. We expected that costs of switching between tasks would be strongly reduced under conditions of small stimulus-set sizes (n=4) as compared to large stimulus-set sizes (n=96) with increasing time on task. The second aim was to determine whether younger as well as older adults were able to create associations between task components. As age differences in task switching are often found to be larger when response mappings are incompatible we also investigated interactions with response compatibility. Results of our study indicated that practice effects on switch costs were much more pronounced for small than large stimulus-set sizes, consistent with the view that the strength of associations between task components facilitates task switching. Furthermore, we found that practice benefits on task switching for small stimulus-set sizes were sensitive to age and response compatibility. In contrast to younger adults, who showed a reduction of switch costs for both response mapping conditions, older adults showed a reduction of switch costs only when response mappings were compatible. That is, older adults showed less associative learning when the currently irrelevant task feature had to be suppressed, supporting the view that older adults have primarily problems in separating overlapping task-set representations.     

Testing the limits of cognitive plasticity in older adults: application to attentional control

Laboratory based training studies suggest that older adults can benefit from training in tasks that tap control aspects of attention. This was further explored in the present study in which older and younger adults completed an adaptive and individualized dual-task training program. The testing-the-limits approach was used [Lindenberger, U., & Baltes, P. B. (1995). Testing-the-limits and experimental simulation: Two methods to explicate the role of learning in development. Human Development, 38, 349-360.] in order to gain insight into how attentional control can be improved in older adults. Results indicated substantial improvement in overlapping task performance in both younger and older participants suggesting the availability of cognitive plasticity in both age groups. Improvement was equivalent among age groups in response speed and performance variability but larger in response accuracy for older adults. The results suggest that time-sharing skills can be substantially improved in older adults.     

Age Influences on Multi-Dimensional Set Switching

Using a task switching paradigm, we investigated age effects on switch costs as a function of the number of sets to be switched. In Experiment 1, younger and older subjects determined a color or shape of an object presented on the computer screen, responding either by moving the joystick or by pressing a button on the joystick. The switch costs were assessed with differences between switch trials (task-set switch, response-set switch, and double switch) and non-switch trials. Contrary to the prediction that age would negatively influence performance on the double switch trials, age effects on switch costs were observed only for the single switch trials (i.e., response-set switch condition). Additionally, both younger and older adults were capable of preparing for task and response-set switches in parallel. In Experiment 2, we manipulated the time available to prepare for a task and response-set switch. Both younger and older adults were able to utilize extra time to reduce switch costs. Furthermore, the age deficit found in Experiment 1 for response-set switching was eliminated in the second experiment in which preparation for task and response-set switching was temporally decoupled. The data are discussed in terms of task component coordination across the adult lifespan.     

Number-processing skills in adults with dyslexia

The present study investigated basic numerical skills and arithmetic in adults with developmental dyslexia. Participants performed exact and approximate calculation, basic numerical tasks (e.g., counting; symbolic number comparison; spatial–numerical association of response codes, SNARC), and visuospatial tasks (mental rotation and visual search tasks). The group with dyslexia showed a marginal impairment in counting compared to age- and IQ-matched controls, and they were impaired in exact addition, in particular with respect to speed. They were also significantly slower in multiplication. In basic number processing, however, there was no significant difference in performance between those with dyslexia and controls. Both groups performed similarly on subtraction and approximate addition tasks. These findings indicate that basic number processing in adults with dyslexia is intact. Their difficulties are restricted to the verbal code and are not associated with deficits in nonverbal magnitude representation, visual Arabic number form, or spatial cognition.     

Age-differential effects on updating cue information: Evidence from event-related potentials

Recent models on cognitive aging consider the ability to maintain and update context information to be a key source of age-related impairments in various cognitive tasks (Braver & Barch in Neuroscience & Biobehavioral Reviews, 26: 809–817, 2002). Context updating has been investigated with a modified AX-continuous-performance task by comparing performance and brain activity between context-dependent trials (i.e., correct responses require updating of the preceding cue information) and context-independent trials (i.e., correct responses are independent of cue information). We used an event-related potential (ERP) approach to identify sources of age differences in context processing in the early and late processing of cue information. Our behavioral data showed longer latencies and higher error rates on context-dependent than on context-independent trials for older than for younger adults, suggesting age-related impairments in context updating. The ERP data revealed larger P3b amplitudes for context-dependent than for context-independent trials only in younger adults. In contrast, in older adults, P3b amplitudes were more evenly distributed across the scalp and did not differ between context conditions. Interestingly, older but not younger adults were sensitive to changes of cue identity, as indicated by larger P3b amplitudes on cue-change than on cue-repeat trials, irrespective of the actual context condition. We also found a larger CNV on context-dependent than on context-independent trials, reflecting active maintenance of context information and response preparation. The age-differential effects in the P3b suggest that both younger and older adults were engaged in updating task-relevant information, but relied on different information: Whereas younger participants indeed relied on context cues to update and reconfigure the task settings, older adults relied on changes in cue identity, irrespective of context information.     

Retrieval-induced forgetting of arithmetic facts but not rules

Retrieval of a multiplication fact (2×6 =12) can disrupt retrieval of its addition counterpart (2+6=8). We investigated whether this retrieval-induced forgetting effect applies to rule-governed arithmetic facts (i.e., 0×N=0, 1×N=N). Participants (n=40) practised rule-governed multiplication problems (e.g., 1×4, 0×5) and multiplication facts (e.g., 2×3, 4×5) for four blocks and then were tested on the addition counterparts (e.g., 1+4, 0+5, 2+3, 4+5) and control additions. Increased addition response times and errors relative to controls occurred only for problems corresponding to multiplication facts, with no problem-specific effects on addition counterparts of rule-governed multiplications. In contrast, the rule-governed 0+N problems provided evidence of generalisation of practice across items, whereas the fact-based 1+N problems did not. These findings support the theory that elementary arithmetic rules and facts involve distinct memory processes, and confirmed that previous, seemly inconsistent findings of RIF in arithmetic owed to the inclusion or exclusion of rule-governed problems.     

中美成年人和老年人数学能力发展的比较研究

采用一套心理计量测验考察中美两国青老年被试在算术能力、知觉速度及空间方位能力方面的操作是否有国家间和年龄组间差异,不同领域之间是否有不同的能力模式。测验结果表明：在知觉速度和空间方位测验上,中美青年组的操作成绩均明显超过老年组;在算术能力测验上,中国青年组的成绩仍超过老年组,但美国青老年组间则无明显差异;中国青年组在算术能力测验上成绩优于美国同龄组,在其它两个测验上则无明显差异;在所有能力测验上中美老年组的成绩都无明显差异;总的模式表明,美国青年的算术能力呈逐代下降趋势,中国儿童和青年的算术能力远远超过美国同龄人的状况可能只是个近期的现象。     

Priming effects in prospective memory

Abstract

The objective of this study was to examine whether an increased activation of knowledge structures facilitates memory for future actions. Priming effects were manipulated by giving subjects a category fluency task for half of the target categories used in the subsequent prospective memory task. In this task, younger and older adults performed an action whenever an instance of a given semantic category occurred in the context of a free association task. The degree of retrieval support was varied by using typical and atypical category instances as targets. Although reliable priming effects were observed for both age groups, the magnitude of priming interacted with the degree of retrieval support. Older adults showed priming effects for typical targets only, whereas the opposite pattern of results was obtained for younger adults. These findings indicate that, in addition to retrieval-related factors, the operations performed at the time of planning also contribute to optimal prospective remembering.     

Lost ability to automatize task performance in old age

Can elderly adults automatize a new task? To address this question, 10 older adults each performed 10,080 training trials over 12 sessions on an easy but novel task. The psychological refractory period (PRP) procedure was then used to evaluate whether this highly practiced task, when presented as task 2 along with an unpracticed task 1, could proceed automatically. If automatic, task 2 processing should bypass the bottleneck and, therefore, not be delayed while central attention is devoted to task 1, yielding little dual-task interference. This is exactly what Maquestiaux, Laguë-Beauvais, Ruthruff, and Bherer (Memory and Cognition 36:1262-1282, 2008) previously observed for almost all younger adults, even with half the training on a more difficult task. Although extensive training reduced older adults’ reaction times to only 307 ms, a value virtually identical to that attained by Maquestiaux et al.’s (Memory and Cognition 36:1262-1282, 2008) younger adults, the highly practiced task 2 was slowed by 485 ms in the dual-task PRP procedure. Such a large slowing in older adults is striking given the easy tasks and massive amounts of practice. These findings demonstrate a qualitative change with age, in which older adults lose the ability to automatize novel tasks, which cannot be attributed merely to generalized cognitive slowing.