Contributions of processing ability and knowledge to verbal memory tasks across the adult life-span

This study investigated the relationships of processing capacity and knowledge to memory measures that varied in retrieval difficulty and reliance on verbal knowledge in an adult life-span sample (N = 341). It was hypothesized that processing ability (speed and working memory) would have the strongest relationship to tasks requiring active retrieval and that knowledge (vocabulary ability) would be related to verbal fluency and cued recall, as participants relied upon verbal knowledge to retrieve category items (fluency) or develop associations (cued recall). Measurement and structural equation models were developed for the entire sample and separately for younger (aged 20-54 years, n = 168) and older (aged 55-92 years, n = 173) subgroups. In accordance with the hypotheses, processing ability was found to be most highly related to free recall, with additional significant relationships to cued recall, verbal fluency, and recognition. Knowledge was found to be significantly related only to verbal fluency and to cued recall. Moreover, knowledge was more important for older than for younger adults in mediating variance in cued recall, suggesting that older adults may use age-related increases in knowledge to partially compensate for processing declines when environmental support is available in memory tasks.     

Measures of fluency as predictors of incidental memory among older adults

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

Investigating the lower level demands of writing: handwriting movements interfere with immediate verbal serial recall

The research identifies if handwriting captures attention for significant periods, resulting in a decline in working memory performance. Additionally, the experiments isolate whether the movements produced during handwriting contribute to that interference. To do this, verbal serial recall was compared between three different tasks???a listening task; a listening?+?handwriting task (i.e., motor and verbal demands); and a listening?+?handwriting-like drawing task (i.e., motor demands), in two experiments. Results showed that verbal serial recall was worse in the handwriting and drawing conditions compared to the listening condition. The handwriting and drawing conditions did not differ. In a third experiment, handwriting fluency was compared between a recall and no-recall task. This showed that handwriting fluency remains stable despite the addition of a verbal working memory task. In conclusion, the handwriting movements capture attention for significant periods, with little deterioration in recall due to the verbal component of handwriting.     

Individual differences in children's memory and reading comprehension: an investigation of semantic and inhibitory deficits

Three experiments compared the verbal memory skills of children with poor reading comprehension with that of same-age good comprehenders. The aims were to determine if semantic and/or inhibitory deficits explained comprehenders' problems on measures of verbal short-term memory and verbal working memory. In Experiment 1 there were no group differences on word- and number-based measures of short-term storage and no evidence that semantic knowledge mediated word recall. In Experiment 2 poor comprehenders were impaired on word- and number-based assessments of working memory, the greatest deficit found on the word-based task. Error analysis of both word-based tasks revealed that poor comprehenders were more likely to recall items that should have been inhibited than were good comprehenders. Experiment 3 extended this finding: Poor comprehenders were less able to inhibit information that was no longer relevant. Together, these findings suggest that individual differences in inhibitory processing influence the ability to regulate the contents of working memory, which may contribute to the differential memory performance of good and poor comprehenders.     

Working memory contributions to reading comprehension components in middle childhood children

This study examined working memory contributions to reading comprehension subskills in Greek children (mean age 9 years, 1 month). The phonological loop of the Baddeley and Hitch working memory model was assessed with 3 recall tasks (words, nonwords, and digits) and a word list matching task. The central executive (CE) was assessed with 3 tasks (listening, counting, and backward digit recall). Participants were also given a receptive vocabulary task, a reading fluency task, and written stories accompanied by comprehension questions. Canonical correlation analyses showed that the comprehension variables were related to the CE rather than the phonological loop measures. CE functions were more strongly associated with elaborative inference generation (involving significant offline processing) and comprehension control (involving metacognitive monitoring). Smaller yet significant associations were observed between the CE and the necessary inference and literal comprehension measures, whereas a moderate relationship was found in the case of the simile comprehension variable. Among the CE variables, listening recall demonstrated the highest loading on the canonical function, followed by moderate yet significant counting and backward digit recall loadings. Vocabulary was found to fully mediate several associations between working memory and comprehension measures; however, the relationship between listening recall and elaborative inferences was partly mediated. Reading fluency and, on several occasions, Greek vocabulary knowledge did not mediate the relationships between CE measures and comprehension skills assessed. This study demonstrates the usefulness of CE measures for identifying young children's possible difficulties in carrying out specific reading comprehension processes.     

The structure of verbal abilities in young and older adults

Four language sample measures as well as measures of vocabulary, verbal fluency, and memory span were obtained from a sample of young adults and a sample of older adults. Factor analysis was used to analyze the structure of the vocabulary, fluency, and span measures for each age group. Then an "extension" analysis was performed by using structural modeling techniques to determine how the language sample measures were related to the other measures. The measure of grammatical complexity was associated with measures of working memory including reading span and digit span. Two measures, sentence length in words and a measure of lexical diversity, were associated with the vocabulary measures. The fourth measure, propositional density, was associated with the fluency measures as a measure of processing efficiency. The structure of verbal abilities in young and older adults is somewhat different, suggesting age differences in processing efficiency.     

Working memory, reading, and mathematical skills in children with developmental coordination disorder

The aim of the present study was investigate the relationship between working memory and reading and mathematical skills in 55 children diagnosed with developmental coordination disorder (DCD). The findings indicate a pervasive memory deficit in all memory measures. In particular, deficits observed in visuospatial short-term and working memory tasks were significantly worse than in the verbal short-term memory ones. On the basis of these deficits, the sample was divided into high and low visuospatial memory ability groups. The low visuospatial memory group performed significantly worse on the attainment measures compared to the high visuospatial memory group, even when the contribution of IQ was taken into account. When the sample was divided into high and low verbal working memory ability groups, verbal working memory skills made a unique contribution to attainment only when verbal IQ was taken into account, but not when performance IQ was statistically controlled. It is possible that the processing demands of the working memory tasks together with the active motor component reflected in the visuospatial memory tasks and performance IQ subtest both play a crucial role in learning in children with DCD.     

The Measurement of Verbal Working Memory Capacity and Its Relation to Reading Comprehension

Ninety-four subjects were tested on the Daneman and Carpenter (1980) reading span task, four versions of a related sentence span task in which reaction times and accuracy on sentence processing were measured along with sentence-final word recall, two number generation tasks designed to test working memory, digit span, and two shape-generation tasks designed to measure visual-spatial working memory. Forty-four subjects were retested on a subset of these measures at a 3-month interval. All subjects were tested on standard vocabulary and reading tests. Correlational analyses showed better internal consistency and test-retest reliability of the sentence span tasks than of the Daneman-Carpenter reading span task. Factor analysis showed no factor that could be related to a central verbal working memory; rotated factors suggested groupings of tests into factors that correspond to digitrelated tasks, spatial tasks, sentence processing in sentence span tasks, and recall in sentence span tasks. Correlational analyses and regression analyses showed that the sentence processing component of the sentence span tasks was the best predictor of performance on the reading test, with a small independent contribution of the recall component. The results suggest that sentence span tasks are unreliable unless measurements are made of both their sentence processing and recall components, and that the predictive value of these tasks for reading comprehension abilities lies in the overlap of operations rather than in limitations in verbal working memory that apply to both.     

Developmental change in the relation between executive functions and symptoms of ADHD and co‐occurring behaviour problems

In a sample of 92 children aged 6–13 years this study investigates the normal developmental change in the relation between executive functioning (EF) and the core behavioural symptoms associated with attention deficit hyperactivity disorder (ADHD) (hyperactivity/impulsivity and inattention) as well as symptoms often co‐occurring with childhood hyperactivity (conduct‐ and internalizing problems). EF was assessed by using multiple tests grouped through prior factor analysis, resulting in cognitive measures relating to disinhibition, speed/arousal, verbal working memory, non‐verbal working memory, and fluency. The results showed that although disinhibition was positively related to hyperactivity/impulsivity and inattention mainly for the youngest age group, there were no significant age effects for these relations. Instead, age effects were found for the relations between speed/arousal and inattention as well as for the relations between verbal working memory/fluency and inattention. In the oldest age group poor performance on these cognitive measures was associated with high ratings of inattention. For the total sample a relation was obtained between disinhibition and hyperactivity/impulsivity as well as between both working memory measures and internalizing problems. In conclusion, the results from this study suggest that poor inhibition is most clearly associated with ADHD symptoms for younger children, whereas poor functioning with regard to later developing and more complex executive functions such as working memory and fluency is associated with ADHD symptoms for older children. Copyright © 2006 John Wiley & Sons, Ltd.     

Asymmetric interference between domains: evidence from the stimulus order effect in complex span tasks

The stimulus order effect refers to the finding that recall in complex span tasks is better when span lists begin with a longer processing task and end with a shorter task than when these processing tasks are presented in the reverse order. This study independently manipulated processing time and processing difficulty between Long-final and Short-final lists. The processing task required participants to solve arithmetic problems with either verbal (Experiment 1) or visuospatial (Experiment 2) materials. The memory items used in the storage task were either digits (verbal material) or dots-in-matrices (visuospatial materials). Storage of both verbal and visuospatial materials was sensitive to the change in processing difficulty, but not processing time. Furthermore, this study provides further evidence for the asymmetry of domain interference in working memory. The similarities and differences between verbal and visuospatial storage in working memory are discussed.     

Monitoring the Changing Status of Semantic Memory in Alzheimer's Disease: An Evaluation of Several Process Measures

The deficits in generating correct words on verbal fluency tasks exhibited by patients with Alzheimer's disease (AD) are accompanied by fewer switching responses, smaller phonemic and semantic cluster sizes, and greater than normal percentages of errors and category labels. On category fluency tasks, patients generate a greater proportion of words that are prototypical of their semantic class. To determine whether any of these supplementary measures of verbal fluency performance might be useful in revealing processes involved in the decline of semantic memory in AD, we studied 219 patients with AD and 115 elderly control participants longitudinally. Previously reported group differences between patients and controls were replicated, but changes in average cluster size, error rates, and prototypicality were not related to changes in overall severity of dementia and test-retest stability was only modest. The change in the percentage of labels generated on the Supermarket task was related to changes in dementia severity, but test-retest stability on this measure was quite low. All of these process measures appear to reflect only the current status of the patient's attention to the task and access to semantic knowledge, but they do not forecast future performance. The numbers of switching responses on the fluency tasks were sensitive to differences between clinically deteriorated and clinically stable patients and showed fairly high test-retest stability. However, the number of switching responses is so highly correlated with the number of correct words that it contributes little to the understanding of the processes involved in the progressive decline in performance on fluency tasks by patients with AD.     

Response selection involves executive control: Evidence from the selective interference paradigm

In the present study, we investigated whether response selection involves executive control, using the selective interference paradigm within Baddeley's (1986) working memory framework. The interference from response selection was estimated by comparing the patterns of dual-task interference of simple and choice RT tasks with those of a number of established working memory tasks. In Experiment 1, we compared impairment of forward and backward verbal serial recall from the RT tasks and articulatory suppression. Experiment 2 measured the adverse effects of the RT tasks and matrix tapping on forward and backward visuospatial serial recall. Finally, in Experiment 3, we examined the impairment from the RT tasks with two measures of executive control--namely, letter and category fluency. Altogether, the three experiments demonstrated that response selection interferes with executive control and that the interference is not produced at the level of working memory's slave systems, which supports the assumption of executive involvement in response selection.     

Working memory as a predictor of written arithmetical skills in children: The importance of central executive functions

Background . The study was conducted in an attempt to further our understanding of how working memory contributes to written arithmetical skills in children. Aim . The aim was to pinpoint the contribution of different central executive functions and to examine the contribution of the two subcomponents of children's written arithmetical skills. Sample and method . A total of 141 third‐ and fourth‐graders were administered arithmetical tasks and measures of working memory, fluid IQ and reading. Regression analysis was used to examine the relationship between working memory and written arithmetical skills. Results . Three central executive measures (counting span, trail making and verbal fluency) and one phonological loop measure (Digit Span) were significant and predictors of arithmetical performance when the influence of reading, age and IQ was controlled for in the analysis. Conclusions . The present findings demonstrate that working memory, in general, and the central executive, in particular, contribute to children's arithmetical skills. It was hypothesized that monitoring and coordinating multiple processes, and accessing arithmetical knowledge from long‐term memory, are important central executive functions during arithmetical performance. The contribution of the phonological loop and the central executive (concurrent processing and storage of numerical information) indicates that children aged 9–10 years primarily utilize verbal coding strategies during written arithmetical performance.     

Neuropsychological functioning in a patient with essential tremor with and without bilateral VIM stimulation

The effects of deep brain stimulation on motor functions, cognitive abilities, and mood were assessed in an 80-year-old, right-handed male with a chronic history of essential tremor. Electrodes were implanted bilaterally in the ventral intermediate nucleus of the thalamus during a single operation. Upon evaluation at 3 months postsurgery, bilateral stimulation was associated with a clinically significant reduction in tremor ratings and improvement in manual dexterity. At that time, a battery of neuropsychological measures was administered with and without bilateral stimulation. The patient demonstrated comparable performances on measures of visuospatial perception, attention, mental tracking, verbal learning, and verbal recognition memory in both the "on" and "off" conditions. Without stimulation, the patient demonstrated declines of greater than 1 SD on measures of verbal fluency and verbal recall compared to when the stimulators were active. Responses to mood rating scales also indicated greater subjective distress without stimulation. Results are discussed in the context of previous studies of the effects of thalamic stimulation on neurocognitive functioning.     

Book Reviews

There is long-standing evidence for verbal working memory impairments in both children and adults with dyslexia. By contrast, spatial memory appears largely to be unimpaired. In an attempt to distinguish between phonological and central executive accounts of the impairments in working memory, a set of phonological and spatial working memory tasks was designed to investigate the key issues in working memory, task type, task demands (static, dynamic, and updating), and task complexity. Significant differences emerged between the dyslexic and nondyslexic participants on the verbal working memory tasks employed in Experiment 1, thereby providing further evidence for continuing dyslexic impairments of working memory into adulthood. The nature of the deficits suggested a problem with the phonological loop, with there being little evidence to implicate an impairment of the central executive. Due to the difficulties associated with separating verbal working memory and phonological processing, however, performance was investigated in Experiment 2 using visuospatial measures of working memory. The results of the visuospatial tasks indicated no between-group differences in static spatial memory, which requires the short-term storage of simultaneously presented information. In almost all conditions there were no between-group differences in dynamic spatial memory that demands the recall of both location and order of stimuli presented sequentially. However, a significant impairment occurred on the dynamic task under high memory updating load, on which dyslexic adults showed nonphonological working memory deficits. In the absence of an explanation involving verbal recoding, this finding is interpreted in terms of a central executive or automaticity impairment in dyslexia.     

Working memory predicts subsequent episodic memory decline during healthy cognitive aging: evidence from a cross-lagged panel design

Aging adults experience declines in working memory and episodic memory, however, it is unclear how these declines operate over time. Decreased working memory may be associated with early changes in episodic memory, by reducing older adults’ ability to meaningfully integrate new information into pre-existing schemas and recall information without the assistance of cues. Given the increased prevalence of Alzheimer’s disease, and concerns based on subjective memory changes, it is important to understand how these processes interact over time. To assess the relationship between working memory and episodic memory during healthy cognitive aging, we performed neuropsychological assessments at multiple time points in a sample of 310 community-dwelling older adults. Using a cross-lagged panel design, we demonstrated that the lagged associations between working memory and later episodic free recall were 50% larger than the lagged associations between episodic recall and later working memory, suggesting working memory may be a useful metric of future episodic memory decline.     

Recall of Subject-Performed Tasks,Verbal Tasks,and Cognitive Activities Across the Adult Life Span: Parallel Age-Related Deficits

Motor activity during encoding of verbal information has been suggested to reduce age differences in episodic memory. Here we examined memory for sentences encoded with enactment (SPTs, subject-performed tasks) or without enactment (VTs, verbal tasks) in a population-based sample consisting of 10 groups ranging in age from 35 to 80 years (N = 1000). Memory performance was assessed by immediate free- and category-cued recall. Degree of clustering was measured by the adjusted ratio of clustering score. Recall of cognitive activities served as a complementary measure of memory for performed tasks. Sentence recall showed a gradual decline across age, of about the same magnitude for SPTs and VTs, in both free and cued recall. Clustering in free recall was higher for SPTs than for VTs, but there were no age differences in clustering. A pattern of gradual decline from age 35 was observed also in activity recall, regardless of whether the activities involved motor activity or not. Across the memory measures, differences in education accounted for all of the age-related variance in performance among the younger (35-55 years) but not the older groups (60-80 years), suggesting that genuine aging effects in these measures are more prominent in old age. Together, the results indicate that age differences in episodic memory, in line with most, if not all, types of encoding support, generalize across the performed/non-performed distinction.     

Linking metaphor comprehension with analogical reasoning: Evidence from typical development and autism spectrum disorder

We examined the relationship between metaphor comprehension and verbal analogical reasoning in young adults who were either typically developing (TD) or diagnosed with Autism Spectrum Disorder (ASD). The ASD sample was highly educated and high in verbal ability, and closely matched to a subset of TD participants on age, gender, educational background, and verbal ability. Additional TD participants with a broader range of abilities were also tested. Each participant solved sets of verbal analogies and metaphors in verification formats, allowing measurement of both accuracy and reaction times. Measures of individual differences in vocabulary, verbal working memory, and autistic traits were also obtained. Accuracy for both the verbal analogy and the metaphor task was very similar across the ASD and matched TD groups. However, reaction times on both tasks were longer for the ASD group. Additionally, stronger correlations between verbal analogical reasoning and working memory capacity in the ASD group indicated that processing verbal analogies was more effortful for them. In the case of both groups, accuracy on the metaphor and analogy tasks was correlated. A mediation analysis revealed that after controlling for working memory capacity, the inter-task correlation could be accounted for by the mediating variable of vocabulary knowledge, suggesting that the primary common mechanisms linking the two tasks involve language skills.     

The effects of marital status on episodic and semantic memory in healthy middle-aged and old individuals

The present study examined the influences of marital status on different episodic and semantic memory tasks. A total of 1882 adult men and women participated in a longitudinal project (Betula) on memory, health and aging. The participants were grouped into two age cohorts, 35-60 and 65-85, and studied over a period of 5 years. Episodic memory tasks concerned recognition and recall, whereas semantic memory tasks concerned knowledge and fluency. The results showed, after controlling for education, some diseases, chronological age and leisure activity as covariates, that there were significant differences between married and single individuals in episodic memory, but not in semantic memory. Married people showed significantly better memory performances than singles in both subsystems of episodic memory, that is, recall and recognition. Also, the rate of decline in episodic memory was significantly larger for singles and widowed than other groups over the 5-year time period in both age groups. The findings demonstrate that the positive relation found between marriage and health can be extended to the relation between marriage and cognitive performance. This effect might be explained by the role played by cognitive stimulation in memory and cognition.