Heather Bailey

Why does working memory span predict complex cognition? Testing the strategy affordance hypothesis

We introduce and empirically evaluate the strategy affordance hypothesis, which holds that individual differences in strategy use will mediate the relationship between performances on a working memory (WM) span task and another cognitive task only when the same strategies are afforded by both tasks. One hundred forty-eight participants completed basic memory tasks and verbal span tasks that afford the same strategies, such as imagery and sentence generation, and completed reading comprehension tasks that afford different ones, such as self-questioning and summarization. Effective strategy use on WM span tasks accounted for variance in the span-memory relationship, but not for the span-comprehension relationship, supporting the strategy affordance hypothesis. Strategy use mediated the span-cognition relationship only when both tasks afforded the same strategies.

Event segmentation ability uniquely predicts event memory.

Memory for everyday events plays a central role in tasks of daily living, autobiographical memory, and planning. Event memory depends in part on segmenting ongoing activity into meaningful units. This study examined the relationship between event segmentation and memory in a lifespan sample to answer the following question: Is the ability to segment activity into meaningful events a unique predictor of subsequent memory, or is the relationship between event perception and memory accounted for by general cognitive abilities? Two hundred and eight adults ranging from 20 to 79years old segmented movies of everyday events and attempted to remember the events afterwards. They also completed psychometric ability tests and tests measuring script knowledge for everyday events. Event segmentation and script knowledge both explained unique variance in event memory above and beyond the psychometric measures, and did so as strongly in older as in younger adults. These results suggest that event segmentation is a basic cognitive mechanism, important for memory across the lifespan.

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.

Action perception predicts action performance

Everyday action impairments often are observed in demented older adults, and they are common potential barriers to functional independence. We evaluated whether the ability to segment and efficiently encode activities is related to the ability to execute activities. Further, we evaluated whether brain regions important for segmentation also were important for action performance. Cognitively healthy older adults and those with very mild or mild dementia of the Alzheimers type watched and segmented movies of everyday activities and then completed the Naturalistic Action Test. Structural MRI was used to measure volume in the dorsolateral prefrontal cortex (DLPFC), medial temporal lobes (MTL), posterior cortex, and anterior cingulate cortex (ACC). Dementia status and the ability to segment everyday activities strongly predicted naturalistic action performance, and MTL volume largely accounted for this relationship. In addition, the current results supported the Omission-Commission Model: Different cognitive and neurological mechanisms predicted different types of action error. Segmentation, dementia severity, and MTL volume predicted everyday omission errors, DLPFC volume predicted commission errors, and ACC volume predicted action additions. These findings suggest that event segmentation may be critical for effective action production, and that the segmentation and production of activities may recruit the same event representation system.

Metacognitive Training at Home: Does It Improve Older Adults’ Learning?

Background: Previous research has described the success of an intervention aimed at improving older adults’ ability to regulate their learning. This metacognitive approach involves teaching older adults to allocate their study time more efficiently by testing themselves and restudying items that are less well learned. Objective: Although this type of memory intervention has shown promise, training older adults to test themselves in the laboratory can be very time-intensive. Thus, the purpose of the present study is to transport the self-testing training method from the laboratory to home use. Methods: A standard intervention design was used that included a pretraining session, multiple training sessions, and a posttraining session. Participants were randomly assigned to either the training group (n = 29) or the waiting list control group (n = 27). Moreover, we screened participants for whether they used the self-testing strategy during their pretraining test session. Results: Compared to the performance of the control group, the training group displayed significant gains, which demonstrates that older adults can benefit from training themselves to use these skills at home. Moreover, the results of the present study indicate that this metacognitive approach can effectively improve older adults’ learning, even in those who spontaneously self-test prior to training. Conclusions: Training metacognitive skills, such as self-testing and efficient study allocation, can improve the ability to learn new information in healthy older adults. More importantly, older adult clients can be supplied with an at-home training manual, which will ease the burden on practitioners.

Medial Temporal Lobe Volume Predicts Elders' Everyday Memory

Deficits in memory for everyday activities are common complaints among healthy and demented older adults. The medial temporal lobes and dorsolateral prefrontal cortex are both affected by aging and early-stage Alzheimer’s disease, and are known to influence performance on laboratory memory tasks. We investigated whether the volume of these structures predicts everyday memory. Cognitively healthy older adults and older adults with mild Alzheimer’s-type dementia watched movies of everyday activities and completed memory tests on the activities. Structural MRI was used to measure brain volume. Medial temporal but not prefrontal volume strongly predicted subsequent memory. Everyday memory depends on segmenting activity into discrete events during perception, and medial temporal volume partially accounted for the relationship between performance on the memory tests and performance on an event-segmentation task. The everyday-memory measures used in this study involve retrieval of episodic and semantic information as well as working memory updating. Thus, the current findings suggest that during perception, the medial temporal lobes support the construction of event representations that determine subsequent memory.

Contribution of strategy use to performance on complex and simple span tasks

Simple and complex span tasks are widely thought to measure related but separable memory constructs. Recently, however, research has demonstrated that simple and complex span tasks may tap, in part, the same construct because both similarly predict performance on measures of fluid intelligence (Gf) when the number of items retrieved from secondary memory (SM) is equated (Unsworth & Engle, Journal of Memory and Language 54:68–80 2006). Two studies (n = 105 and n = 152) evaluated whether retrieval from SM is influenced by individual differences in the use of encoding strategies during span tasks. Results demonstrated that, after equating the number of items retrieved from SM, simple and complex span performance similarly predicted Gf performance, but rates of effective strategy use did not mediate the span-Gf relationships. Moreover, at the level of individual differences, effective strategy use was more highly related to complex span performance than to simple span performance. Thus, even though individual differences in effective strategy use influenced span performance on trials that required retrieval from SM, strategic behavior at encoding cannot account for the similarities between simple and complex span tasks.

Content-embedded tasks beat complex span for predicting comprehension

Discourse comprehension requires one to process information that is actively maintained in working memory (WM). Therefore, we hypothesized that individual differences in comprehension would be predicted better by working memory tasks that capture the concurrent demands of processing and maintenance of the same memory elements (i.e., content-embedded tasks) than by WM tasks that require the maintenance of an extraneous memory load during processing (e.g., complex span tasks). Two hundred sixty-one undergraduates completed three content-embedded tasks, three complex span tasks, and three measures of comprehension. Results of structural equation modeling indicated that the content-embedded tasks accounted for a greater amount of variance in comprehension than did complex span tasks. Thus, tasks that require one to coordinate the processing and maintenance of task-specific memory elements are preferable for capturing the relationship between WM and comprehension.

Does Strategy Training Reduce Age-Related Deficits in Working Memory?

Background: Older adults typically perform worse on measures of working memory (WM) than do young adults; however, age-related differences in WM performance might be reduced if older adults use effective encoding strategies. Objective: The purpose of the current experiment was to evaluate WM performance after training individuals to use effective encoding strategies. Methods: Participants in the training group (older adults: n = 39; young adults: n = 41) were taught about various verbal encoding strategies and their differential effectiveness and were trained to use interactive imagery and sentence generation on a list-learning task. Participants in the control group (older: n = 37; young: n = 38) completed an equally engaging filler task. All participants completed a pre- and post-training reading span task, which included self-reported strategy use, as well as two transfer tasks that differed in the affordance to use the trained strategies - a paired-associate recall task and the self-ordered pointing task. Results: Both young and older adults were able to use the target strategies on the WM task and showed gains in WM performance after training. The age-related WM deficit was not greatly affected, however, and the training gains did not transfer to the other cognitive tasks. In fact, participants attempted to adapt the trained strategies for a paired-associate recall task, but the increased strategy use did not benefit their performance. Conclusions: Strategy training can boost WM performance, and its benefits appear to arise from strategy-specific effects and not from domain-general gains in cognitive ability.

Event segmentation improves event memory up to one month later.

When people observe everyday activity, they spontaneously parse it into discrete meaningful events. Individuals who segment activity in a more normative fashion show better subsequent memory for the events. If segmenting events effectively leads to better memory, does asking people to attend to segmentation improve subsequent memory? To answer this question, participants viewed movies of naturalistic activity with instructions to remember the activity for a later test, and in some conditions additionally pressed a button to segment the movies into meaningful events or performed a control condition that required button-pressing but not attending to segmentation. In 5 experiments, memory for the movies was assessed at intervals ranging from immediately following viewing to 1 month later. Performing the event segmentation task led to superior memory at delays ranging from 10 min to 1 month. Further, individual differences in segmentation ability predicted individual differences in memory performance for up to a month following encoding. This study provides the first evidence that manipulating event segmentation affects memory over long delays and that individual differences in event segmentation are related to differences in memory over long delays. These effects suggest that attending to how an activity breaks down into meaningful events contributes to memory formation. Instructing people to more effectively segment events may serve as a potential intervention to alleviate everyday memory complaints in aging and clinical populations.