Aging, focus switching, and task switching in a continuous calculation task: evidence toward a new working memory control process

Memory for linguistic features and the focus of attention: evidence from the dynamics of agreement inside DP

The amount of information that can be concurrently maintained in the focus of attention is strongly restricted (Broadbent, 1958). The goal of this study was to test whether this restriction was functionally significant for language comprehension. We examined the time course dynamics of processing determiner-head agreement in English demonstrative phrases. We found evidence that agreement processing was slowed when determiner and head were no longer adjacent, but separated by modifiers. We argue that some information is shunted nearly immediately from the focus of attention, necessitating its later retrieval. Plural, the marked feature value for number, exhibits better preservation in the focus of attention, however, than the unmarked value, singular.

Age Differences in the Subcomponents of Executive Functioning

OBJECTIVES

Across the life span, deficits in executive functioning (EF) are associated with poor behavioral control and failure to achieve goals. Though EF is often discussed as one broad construct, a prominent model of EF suggests that it is composed of three subdomains: inhibition, set shifting, and updating. These subdomains are seen in both younger (YA) and older adults (OA), with performance deficits across subdomains in OA. Therefore, our goal was to investigate whether subdomains of EF might be differentially affected by age, and how these differences may relate to broader global age differences in EF.

METHODS

To assess these age differences, we conducted a meta-analysis at multiple levels, including task level, subdomain level, and of global EF. Based on previous work, we hypothesized that there would be overall differences in EF in OA.

RESULTS

Using 1,268 effect sizes from 401 articles, we found overall differences in EF with age. Results suggested that differences in performance are not uniform, such that variability in age effects emerged at the task level, and updating was not as affected by age as other subdomains.

DISCUSSION

These findings advance our understanding of age differences in EF, and stand to inform early detection of EF decline.

Aging Influences the Efficiency of Attentional Maintenance in Verbal Working Memory

OBJECTIVES

Numerous studies reported an age-related deficit in verbal working memory (WM). Beyond the well-established general factors of cognitive aging, the alteration of the specific WM maintenance mechanisms may account for this deficit. This paper aims to investigate the hypothesis that WM attentional maintenance is impaired with age.

METHOD

In a WM task adapted to individual short-term memory and processing speed, younger and older participants maintained letters while verbally responding to a concurrent processing task, in order to constrain the use of rehearsal. Critically, the opportunity to use attentional maintenance was manipulated by varying the cognitive load (CL) of the concurrent processing via its nature and pace.

RESULTS

Younger participants outperformed older participants and, in both groups, recall performance decreased as the CL increased. Importantly, in line with our predictions, the CL effect was modulated by age. Older adults benefited less from free pauses that allowed participants to engage in attentional maintenance of WM traces.

DISCUSSION

Although still effective in normal aging, WM attentional maintenance seems to be altered. It could therefore be a good candidate to account for WM age-related deficits.

Resolving Age-Related Differences in Working Memory: Equating Perception and Attention Makes Older Adults Remember as Well as Younger Adults

OBJECTIVES

Older adults show clear deficits in working memory functioning. Here, we investigate the often-reported decline in focus switching, that is, the ability to shift items from the focus of attention into working memory, and back. Specifically, we examined whether equating subjects on early processing (perception and attention) might ameliorate the deficit.

METHOD

We examined 1-Back and 2-Back performance in younger and older adults, with line segments of different orientation as the stimuli. Stimuli were calibrated depending on each individual's 75% threshold for 1-Back performance. Subjects made match/mismatch judgments.

RESULTS

After the calibration on 1-Back performance, no age-related differences were found on either accuracy or sensitivity in the 2-Back task. Additionally, when investigating focus-switch trials versus non-focus-switch trials in a random-order 2-Back task, older adults were more efficient at switching the focus of attention than younger adults.

DISCUSSION

These results provide evidence for the view that age-related limitations in focus switching in working memory are caused (at least in part) by changes in early processing (perception and attention), suggesting that (at least some of the) age-related differences in working memory functioning may be due to shifts in trade-off between early processing and memory-related processing.

Visual Impairment Was Related to Educational Level but Not to Cognitive Performance Among Adults in Their 60s

Background

Older people are at greater risk of both physical impairments and cognitive decline. Although previous studies have examined whether visual and cognitive impairments are associated, findings have been mixed with cognitive performance only crudely assessed. Nonetheless, it remains possible that this association becomes stronger with age. Accordingly, in the present study, we tested the hypothesis that older people with visual impairments have poorer cognitive performance than healthy controls. To this end, we employed validated tools to assess both visual-related and visual-unrelated cognitive skills.

Methods

A total of 30 older adults (mean age: M = 63.98 years, 30% females) with poor vision (logMAR value 1.0 or higher) and 30 gender- and age-matched healthy controls with no visual impairments (logMAR value 0.2 or lower) took part in this cross-sectional study. After a careful medical and psychiatric examination, participants underwent thorough cognitive testing for working and long-term memory and attention.

Results

Cognitive performance did not differ between those with and without visual impairments, though better cognitive performance scores were associated with higher educational level.

Conclusions

Among older people, visual impairment was unrelated to cognitive performance. Rather, cognitive function was related to level of education.

Focus Switching in Working Memory

Abstract. Focus switching in working memory involves accessing an object in the focus of attention in order to retrieve its content. Objects in working memory can be viewed as consisting of two types of information: contents (e.g., numerical information) and contexts (e.g., cues to retrieve the contents). This study examined the extent to which content retrieval and context access may be separated. Three experiments were carried out in which object switching and content retrieval were manipulated. In addition, the alternation between the retrieval operations was also manipulated. The main result was that content retrieval required time over and above that needed to access the object. This finding supports the idea that contexts and their contents may be accessed independently when an object is brought into the focus.

Is refreshing in working memory impaired in older age? Evidence from the retro-cue paradigm

Impairments in refreshing have been suggested as one source of working memory (WM) deficits in older age. Retro-cues provide an important method of investigating this question: a retro-cue guides attention to one WM item, thereby arguably refreshing it and increasing its accessibility compared with a no-cue baseline. In contrast to the refreshing deficit hypothesis, intact retro-cue benefits have been found in older adults. Refreshing, however, is assumed to boost not one but several WM representations when sequentially applied to them. Hence, intact refreshing requires the flexible switching of attention among WM items. So far, it remains an open question whether older adults show this flexibility. Here, we investigated whether older adults can use multiple cues to sequentially refresh WM representations. Younger and older adults completed a continuous-color delayed-estimation task, in which the number of retro-cues (0, 1, or 2) presented during the retention interval was manipulated. The results showed a similar retro-cue benefit for younger and older adults, even in the two-cue condition in which participants had to switch attention between items to refresh representations in WM. These findings suggest that the capacity to use cues to refresh information in visual WM may be preserved with age.

Visual Acuity does not Moderate Effect Sizes of Higher-Level Cognitive Tasks

BACKGROUND/STUDY CONTEXT

Declining visual capacities in older adults have been posited as a driving force behind adult age differences in higher-order cognitive functions (e.g., the "common cause" hypothesis of Lindenberger & Baltes, 1994, Psychology and Aging, 9, 339-355). McGowan, Patterson, and Jordan (2013, Experimental Aging Research, 39, 70-79) also found that a surprisingly large number of published cognitive aging studies failed to include adequate measures of visual acuity. However, a recent meta-analysis of three studies (La Fleur and Salthouse, 2014, Psychonomic Bulletin & Review, 21, 1202-1208) failed to find evidence that visual acuity moderated or mediated age differences in higher-level cognitive processes. In order to provide a more extensive test of whether visual acuity moderates age differences in higher-level cognitive processes, we conducted a more extensive meta-analysis of topic.

METHODS

Using results from 456 studies, we calculated effect sizes for the main effect of age across four cognitive domains (attention, executive function, memory, and perception/language) separately for five levels of visual acuity criteria (no criteria, undisclosed criteria, self-reported acuity, 20/80-20/31, and 20/30 or better).

RESULTS

As expected, age had a significant effect on each cognitive domain. However, these age effects did not further differ as a function of visual acuity criteria.

CONCLUSION

The current meta-analytic, cross-sectional results suggest that visual acuity is not significantly related to age group differences in higher-level cognitive performance-thereby replicating La Fleur and Salthouse (2014). Further efforts are needed to determine whether other measures of visual functioning (e.g., contrast sensitivity, luminance) affect age differences in cognitive functioning.

Differential Effects of Executive Processes on Working Memory

Abstract. Although attention control accounts for a unique portion of the variance in working memory capacity (WMC), the way in which attention control contributes to WMC has not been thoroughly specified. The current work focused on fractionating attention control into distinctly different executive processes and examined to what extent key processes of attention control including updating, shifting, and prepotent response inhibition were related to WMC and whether these relations were different. A number of 216 university students completed experimental tasks of attention control and two measures of WMC. Latent variable analyses were employed for separating and modeling each process and their effects on WMC. The results showed that both the accuracy of updating and shifting were substantially related to WMC while the link from the accuracy of inhibition to WMC was insignificant; on the other hand, only the speed of shifting had a moderate effect on WMC while neither the speed of updating nor the speed of inhibition showed significant effect on WMC. The results suggest that these key processes of attention control exhibit differential effects on individual differences in WMC. The approach that combined experimental manipulations and statistical modeling constitutes a promising way of investigating cognitive processes.

The neural language systems that support healthy aging: Integrating function, structure, and behavior

Although healthy aging is generally characterized by declines in both brain structure and function, there is variability in the extent to which these changes result in observable cognitive decline. Specific to language, age-related differences in language production are observed more frequently than in language comprehension, although both are associated with increased right prefrontal cortex activation in older adults. The current paper explores these differences in the language system, integrating them with theories of behavioral and neural cognitive aging. Overall, data indicate that frontal reorganization of the dorsal language stream in older adults benefits task performance during comprehension, but not always during production. We interpret these results in the CRUNCH framework (compensation-related utilization of neural circuits hypothesis), which suggests that differences in task and process difficulty may underlie older adults' ability to successfully adapt. That is, older adults may be able to neurally adapt to less difficult tasks (i.e., comprehension), but fail to do so successfully as difficulty increases (i.e., production). We hypothesize greater age-related differences in aspects of language that rely more heavily on the dorsal language stream (e.g., syntax and production) and that recruit general cognitive resources that rely on frontal regions (e.g., executive function, working memory, inhibition). Moreover, there should be a relative sparing of tasks that rely predominantly on ventral stream regions. These results are both consistent with patterns of age-related structural decline and retention and with varying levels of difficulty across comprehension and production. This neurocognitive framework for understanding age-related differences in the language system centers on the interaction between prefrontal cortex activation, structural integrity, and task difficulty.

Age-related differences in working memory updating components

The aim of this study was to investigate possible age-related changes throughout childhood and adolescence in different component processes of working memory updating (WMU): retrieval, transformation, and substitution. A set of numerical WMU tasks was administered to four age groups (8-, 11-, 14-, and 21-year-olds). To isolate the effect of each of the WMU components, participants performed different versions of a task that included different combinations of the WMU components. The results showed an expected overall decrease in response times and an increase in accuracy performance with age. Most important, specific age-related changes in the retrieval component were found, demonstrating that the effect of retrieval on accuracy was larger in children than in adolescents or young adults. These findings indicate that the availability of representations from outside the focus of attention may change with age. Thus, the retrieval component of updating could contribute to the age-related changes observed in the performance of many updating tasks.

Age differences in working memory updating: the role of interference, focus switching and substituting information

Working memory updating (WMU) tasks require different elements in working memory (WM) to be maintained simultaneously, accessing one of these elements, and substituting its content. This study examined possible developmental changes from childhood to adulthood both in focus switching and substituting information in WM. In addition, possible age-related changes in interference due to representational overlap between the different elements simultaneously held in these tasks were examined. Children (8- and 11-year-olds), adolescents (14-year-olds) and younger adults (mean age=22 years) were administered a numerical updating memory task, in which updating and focus switching were manipulated. As expected, response times decreased and recall performance increased with age. More importantly, the time needed for focus switching was longer in children than in adolescents and younger adults. On the other hand, substitution of information and interference due to representational overlap were not affected by age. These results suggest that age-related changes in focus switching might mediate developmental changes in WMU performance.

Is consistency a domain-general individual differences characteristic?

We explored randomness in responding in two ways across six experiments. First, we predicted that people would differ from each other in randomness in a stable way when tested in the same domain across two sessions; people who responded more randomly in a particular domain in one session also should respond more randomly in a second session whereas people who responded less randomly in one session also should respond less randomly in a second session. Second, we predicted that there would be some domain general randomness; people's randomness in one domain should predict their randomness in another domain. We used consistency coefficients across blocks of a session as an inverse measure of randomness and found (a) consistency coefficients correlated across sessions within the same domain and (b) consistency coefficients in one domain correlated with consistency coefficients in other domains.

Rethinking volitional control over task choice in multitask environments: use of a stimulus set selection strategy in voluntary task switching

Under conditions of volitional control in multitask environments, subjects may engage in a variety of strategies to guide task selection. The current research examines whether subjects may sometimes use a top-down control strategy of selecting a task-irrelevant stimulus dimension, such as location, to guide task selection. We term this approach a stimulus set selection strategy. Using a voluntary task switching procedure, subjects voluntarily switched between categorizing letter and number stimuli that appeared in two, four, or eight possible target locations. Effects of stimulus availability, manipulated by varying the stimulus onset asynchrony between the two target stimuli, and location repetition were analysed to assess the use of a stimulus set selection strategy. Considered across position condition, Experiment 1 showed effects of both stimulus availability and location repetition on task choice suggesting that only in the 2-position condition, where selection based on location always results in a target at the selected location, subjects may have been using a stimulus set selection strategy on some trials. Experiment 2 replicated and extended these findings in a visually more cluttered environment. These results indicate that, contrary to current models of task selection in voluntary task switching, the top-down control of task selection may occur in the absence of the formation of an intention to perform a particular task.

Analogous mechanisms of selection and updating in declarative and procedural working memory: experiments and a computational model

The article investigates the mechanisms of selecting and updating representations in declarative and procedural working memory (WM). Declarative WM holds the objects of thought available, whereas procedural WM holds representations of what to do with these objects. Both systems consist of three embedded components: activated long-term memory, a central capacity-limited component for building structures through temporary bindings, and a single-element focus of attention. Five experiments test the hypothesis of analogous mechanisms in declarative and procedural WM, investigating repetition effects across trials for individual representations (objects and responses) and for sets (memory sets and task sets), as well as set-congruency effects. Evidence for analogous processes was obtained from three phenomena: (1) Costs of task switching and of list switching are reduced with longer preparation interval. (2) The effects of task congruency and of list congruency are undiminished with longer preparation interval. (3) Response repetition interacts with task repetition in procedural WM; here we show an analogous interaction of list repetition with item repetition in declarative WM. All three patterns were reproduced by a connectionist model implementing the assumed selection and updating mechanisms. The model consists of two modules, an item-selection module selecting individual items from a memory set, or responses from a task set, and a set-selection module for selecting memory sets or task sets. The model codes the matrix of binding weights in the item-selection module as a pattern of activation in the set-selection module, thereby providing a mechanism for building chunks in LTM, and for unpacking them as structures into working memory.

Temporal-contextual processing in working memory: evidence from delayed cued recall and delayed free recall tests

Three experiments are reported that addressed the nature of processing in working memory by investigating patterns of delayed cued recall and free recall of items initially studied during complex and simple span tasks. In Experiment 1, items initially studied during a complex span task (i.e., operation span) were more likely to be recalled after a delay in response to temporal-contextual cues, relative to items from subspan and supraspan list lengths in a simple span task (i.e., word span). In Experiment 2, items initially studied during operation span were more likely to be recalled from neighboring serial positions during delayed free recall than were items studied during word span trials. Experiment 3 demonstrated that the number of attentional refreshing opportunities strongly predicts episodic memory performance, regardless of whether the information is presented in a spaced or massed format in a modified operation span task. The results indicate that the content-context bindings created during complex span trials reflect attentional refreshing opportunities that are used to maintain items in working memory.

Similarity-Based Interference in a Working Memory Numerical Updating Task

Similarity among representations held simultaneously in working memory (WM) is a factor which increases interference and hinders performance. The aim of the current study was to investigate age-related differences between younger and older adults in a working memory numerical updating task, in which the similarity between information held in WM was manipulated. Results showed a higher susceptibility of older adults to similarity-based interference when accuracy, and not response times, was considered. It was concluded that older adults’ WM difficulties appear to be due to the availability of stored information, which, in turn, might be related to the ability to generate distinctive representations and to the process of binding such representations to their context when similar information has to be processed in WM.

Aging and executive functioning: a training study on focus-switching

Many studies suggest that age differences in a variety of cognitive tasks are due to age-related changes in executive control processes. However, not all executive control processes seem to be age-sensitive. Recently, Verhaeghen et al. (2005) described dissociable age effects in an executive control process responsible for the switching of representations between different functional units of working memory. This so called focus-switching process has two components: (1) the switching of representations from an activated part of long-term memory into a region of immediate access (focus of attention) and (2) the maintenance of representations outside the focus of attention. Age-related deficits occurred in maintaining representations outside the focus of attention, but were absent in switching representations into and out of the focus of attention (e.g., Dorbath and Titz, 2011). In the present study we applied a training approach to examine age-related differences in the trainability of maintenance and switching. We investigated 85 younger (age 19–35, M = 24.07, SD = 3.79) and 91 older (age 59–80, M = 66.27, SD = 4.75) adults using a continuous counting task in a pretest–training–posttest design. The participants were assigned to one of four training conditions differing in the demand to switch or to maintain. The results suggest the influence of training in both components of focus-switching for both, younger and older adults. However, age differences in the amount of training gains were observed. With respect to maintenance the results indicate a compensatory effect of training for older adults who improved their performance to the level of younger adults. With respect to switching, younger adults benefited more from training than older adults. Trainability is thus reduced in older adults with respect to switching, but not for maintenance.

When the tail counts: the advantage of bilingualism through the ex-gaussian distribution analysis

Several studies have documented the advantage of bilingualism with respect to the development of the executive control (EC) system. Two effects of bilingualism have been described in conflict resolution tasks: (a) bilinguals tend to perform the tasks faster overall, and (b) bilinguals tend to experience less interference from conflicting information, compared to monolinguals. The precise way in which the bilingual advantage relies on different EC mechanisms is still not well understood. The goal of the present article is to further explore how bilingualism impacts the EC system by performing a new analysis (Ex-Gaussian) of already reported data in which bilinguals and monolinguals performed a flanker task. Ex-Gaussian distribution analysis allows us to partial out the contribution of the normal and the exponential components of the RT distribution of the two groups. The fit of the raw data to the ex-Gaussian distribution showed two main results. First, we found that the bilingualism advantage in the overall speed of processing is captured by group differences in the normal (μ) and the exponential (τ) components of the distribution. Second, the bilingual advantage in the magnitude of the conflict effect is captured by group differences only in the exponential component. The results are discussed in terms of: (a) usefulness of the ex-Gaussian analysis as a tool to better describe the RT distribution, and (b) a new approach to explore the cognitive processes purportedly involved in instantiating the bilingualism advantage with respect to EC.

Dissociable Age Effects in Focus-Switching

Focus-switching has recently been identified as an executive control process with differential age sensitivity. To date, the assumption of dissociable age effects is based on only two kinds of tasks constricting its conclusiveness. In a study with 85 younger (19–35 years) and 91 older adults (59–80 years), age effects were again dissociable in two alternative tasks with respect to the availability and the accessibility of representations. The results validate earlier findings that focus-switching is primarily affected in maintaining representations rather than in accessing them.

Aging and switching the focus of attention in working memory: age differences in item availability but not in item accessibility

OBJECTIVES

To investigate age differences in working memory processing, specifically the accuracy of retrieval of items stored outside the immediate focus of attention.

METHODS

Younger and older adults were tested on a modified N-Back task with probes presented in an unpredictable order (implying also that some trials necessitated a switch in the focus of attention and others that did not).

RESULTS

Older adults showed intact item accessibility, that is, after taking general slowing into account, older adults were as fast as younger adults in locating the item in working memory. We found age differences, however, in item availability: Older adults were less likely to correctly retrieve items stored outside the focus of attention. Smaller age differences in availability were also found for items stored inside the focus of attention.

DISCUSSION

These results strongly suggest that item availability is a cognitive primitive that is not reducible to more basic constructs such as item accessibility or simple speed of processing.

Aging, hearing acuity, and the attentional costs of effortful listening

A dual-task interference paradigm was used to investigate the effect of perceptual effort on recall of spoken word lists by young and older adults with good hearing and with mild-to-moderate hearing loss. In addition to poorer recall accuracy, listeners with hearing loss, especially older adults, showed larger secondary task costs while recalling the word lists even though the stimuli were presented at a sound intensity that allowed correct word identification. Findings support the hypothesis that extra effort at the sensory-perceptual level attendant to hearing loss has negative consequences to downstream recall, an effect that may be further magnified with increased age.

Predictive knowledge of stimulus relevance does not influence top-down suppression of irrelevant information in older adults

Our ability to focus attention on task-relevant stimuli and ignore irrelevant distractions is reflected by differential enhancement and suppression of neural activity in sensory cortices. Previous research has shown that older adults exhibit a deficit in suppressing task-irrelevant information, the magnitude of which is associated with a decline in working memory performance. However, it remains unclear if a failure to suppress is a reflection of an inability of older adults to rapidly assess the relevance of information upon stimulus presentation when they are not aware of the relevance beforehand. To address this, we recorded the electroencephalogram (EEG) in healthy older participants (aged 60-80 years) while they performed two different versions of a selective face/scene working memory task, both with and without prior knowledge as to when relevant and irrelevant stimuli would appear. Each trial contained two faces and two scenes presented sequentially followed by a 9 sec delay and a probe stimulus. Participants were given the following instructions: remember faces (ignore scenes), remember scenes (ignore faces), remember the xth and yth stimuli (where x and y could be 1st, 2nd, 3rd or 4th), or passively view all stimuli. Working memory performance remained consistent regardless of task instructions. Enhanced neural activity was observed at posterior electrodes to attended stimuli, while neural responses that reflected the suppression of irrelevant stimuli was absent for both tasks. The lack of significant suppression at early stages of visual processing was revealed by P1 amplitude and N1 latency modulation indices. These results reveal that prior knowledge of stimulus relevance does not modify early neural processing during stimulus encoding and does not improve working memory performance in older adults. These results suggest that the inability to suppress irrelevant information early in the visual processing stream by older adults is related to mechanisms specific to top-down suppression.

Education does not protect against age-related decline of switching focal attention in working memory

In this experimental study, effects of age and education on switching focal attention in working memory were investigated among 44 young (20-30 years) and 40 middle-aged individuals (50-60 years). To this end, a numeric n-back task comprising two lag conditions (1- and 2-back) was administered within groups. The results revealed a comparable increase of reaction time as a function of lag across age groups, but a disproportionate decrease of accuracy in the middle-aged relative to the young group. The latter effect did not interact with education, which challenges the cognitive reserve hypothesis. Moreover, the high-educated middle-aged participants showed a greater increase of reaction time as a function of lag than their low-educated counterparts. Apparently, they were not able to sustain their relatively high response speed across conditions. These results suggest that education does not protect against age-related decline of switching focal attention in working memory.