Working memory and intelligence in children: What develops?

This study explored the contribution of the phonological and executive working memory (WM) systems to 205 (102 girls, 103 boys, 6 to 9 years old) elementary school children's fluid and crystallized intelligence. The results show that (a) a 3-factor structure (phonological short-term memory [STM], visual-spatial WM, and verbal WM) was comparable between age groups, (b) controlled attention and STM storage accounted for 67% of the age-related variance in WM, (c) effect sizes for direct paths from WM were substantially larger when predicting fluid intelligence than crystallized intelligence, and (d) the contribution of STM to intelligence was isolated to reading. The results suggest that the development of WM is distinct from STM, controlled attention plus storage accounted for age-related WM changes, and WM underlies age-related changes in both fluid and crystallized intelligence. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Cross-sectional and incremental changes in working memory and mathematical problem solving.

Cross-sectional and incremental age effects on cognitive processes that underlie individual differences in components of working memory (WM; phonological loop, visual-spatial sketchpad, executive processing) and mathematical problem-solving accuracy were examined in elementary schoolchildren. A battery of tests was administered that assessed problem solving, achievement, memory, and cognitive processing (inhibition, speed, phonological coding) in children in Grades 1, 2, and 3 (Wave 1) and 1 year later (Wave 2). The results showed that (a) 31% of the explainable within-person changes across testing waves and 42% of the age-related differences in word problem-solving accuracy were related to executive processing and (b) executive processing and reading performance in Year 1 were the only variables that contributed unique variance to Year 2 problem-solving performance. The results support the notion that growth in the executive system is an important predictor of children's problem solving abilities beyond the contribution of reading and calculation skills and that growth in executive processing can operate independently of individual differences in phonological processing, inhibition, and processing speed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Growth in working memory and mathematical problem solving in children at risk and not at risk for serious math difficulties.

The influence of cognitive growth in working memory (WM) on mathematical problem solution accuracy was examined in elementary school children (N = 353) at risk and not at risk for serious math problem solving difficulties. A battery of tests was administered that assessed problem solving, achievement, and cognitive processing (WM, inhibition, naming speed, phonological coding) in children in 1st, 2nd, and 3rd grade across 3 testing waves. The results were that (a) children identified as at risk for serious math problem solving difficulties in Wave 1 showed less growth rate and lower levels of performance on cognitive measures than did children not at risk; (b) fluid intelligence and 2 components of WM (central executive, visual-spatial sketchpad) in Wave 1 (Year 1) predicted Wave 3 word problem solving solution accuracy; and (c) growth in the central executive and phonological storage component of WM was related to growth in solution accuracy. The results support the notion that growth in WM is an important predictor of children's problem solving beyond the contribution of reading, calculation skills, and individual differences in phonological processing, inhibition, and processing speed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Literacy and Cognitive Functioning in Bilingual and Nonbilingual Children at or Not at Risk for Reading Disabilities.

The authors determined whether the cognitive processes that underlie second-language acquisition difficulties are the same as those that underlie reading difficulties. First-grade (N = 101) bilingual and nonbilingual children were administered a battery of measures in Spanish and English. English word identification and vocabulary were predicted by a language-general working-memory (WM) factor, whereas English pseudoword reading was predicted by Spanish pseudoword reading and WM. The results also showed that (a) children proficient in language were better able to access resources from WM and (b) children with reading disabilities (RD) performed poorly on Spanish measures of short-term memory. In general, second-language difficulties are related to accessing a language-independent WM system, whereas language-specific phonological memory deficits underlie RD. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The Relationship Between Working Memory and Mathematical Problem Solving in Children at Risk and Not at Risk for Serious Math Difficulties.

This study identified cognitive processes that underlie individual differences in working memory (WM) and mathematical problem-solution accuracy in elementary school children at risk and not at risk for serious math difficulties (SMD). A battery of tests was administered that assessed problem solving, achievement, and cognitive processing in children in first (N = 130), second (N = 92) and third grades (N = 131). The results were that (a) younger children and children at risk for SMD performed poorer on WM and problem-solving tasks, as well as measures of math calculation, reading, semantic processing, phonological processing, and inhibition, than older children and children not at risk for SMD and (b) WM predicted solution accuracy of word problems independent of measures of fluid intelligence, reading skill, math skill, knowledge of algorithms, phonological processing, semantic processing,'speed, shortterm memory, and inhibition. The results support the notion that the executive system is an important predictor of children's problem solving. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Age and working memory: The role of perceptual speed, the central executive, and the phonological loop.

In a study (N?=?61) comparing older (age range?=?60–80 years, M?=?67) and younger (age range?=?20-33 years, M?=?25) people, age deficits were observed in working memory, perceptual speed, and central executive functioning but not in phonological loop functioning. Controlling for age differences in central executive performance removed over 50% of the age-related variance in working memory span. However, controlling for perceptual speed removed all of the age-related variance in working memory span. In addition, age differences in central executive functioning were largely eliminated after controlling for age deficits in perceptual speed. These findings suggest that age differences in central executive functioning are primarily attributable to a general slowdown in the rate at which information is activated within the working memory system and that no specific deficits in the central executive occur as a consequence of aging. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Reading comprehension and working memory in learning-disabled readers: Is the phonological loop more important than the executive system?

This investigation explores the contribution of two working memory systems (the articulatory loop and the central executive) to the performance differences between learning-disabled (LD) and skilled readers. Performances of LD, chronological age (CA) matched, and reading level-matched children were compared on measures of phonological processing accuracy and speed (articulatory system), long-term memory (LTM) accuracy and speed, and executive processing. The results indicated that (a) LD readers were inferior on measures of articulatory, LTM, and executive processing; (b) LD readers were superior to RL readers on measures of executive processing, but were comparable to RL readers on measures of the articulatory and LTM system; (c) executive processing differences remained significant between LD and CA-matched children when measures of reading comprehension, articulatory processes, and LTM processes were partialed from the analysis; and (d) executive processing contributed significant variance to reading comprehension when measures of the articulatory and LTM systems were entered into a hierarchical regression model. In summary, LD readers experience constraints in the articulatory and LTM system, but constraints mediate only some of the influence of executive processing on reading comprehension. Further, LD readers suffer executive processing problems nonspecific to their reading comprehension problems.     

Cognitive processing deficits in poor readers with symptoms of reading disabilities and ADHD: More alike than different?

The cognitive differences among poor-reading children with characteristics of reading disabilities (RD) and attention deficit-hyperactivity disorder (ADHD) when compared with children with comorbid symptoms (RD + ADHD) and slow learners (SL) on measures of phonological and executive processing were investigated. No significant differences in performance emerged between the ability groups in phonological processing. The SL + ADHD & slow learners performed better than RD groups (RD alone and RD + ADHD) on the visual-spatial working memory (WM) factor score and the RD-alone group was inferior to RD + ADHD, SL + ADHD, and SL-alone groups on the verbal WM factor score. The results support the notion that poor readers, whether suffering from RD or ADHD symptoms, share a common phonological core deficit. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Exploring developmental differences in visual short-term memory and working memory.

Although visuospatial short-term memory tasks have been found to engage more executive resources than do their phonological counterparts, it remains unclear whether this is due to intrinsic differences between the tasks or differences in participants’ experience with them. The authors found 11-year-olds’ performances on both visual short-term and working memory tasks to be more greatly impaired by an executive suppression task (random number generation) than were those of 8-year-olds. Similar findings with adults (e.g., Kane & Engle, 2000) suggest that the imposition of a suppression task may have overloaded the older children’s executive resources, which would otherwise be used for deploying strategies for performing the primary tasks. Conversely, the younger children, who probably never had the capacity or know-how to engage these facilitative strategies in the first place, performed more poorly in the single task condition but were less affected in the dual task condition. These findings suggest that differences in the children’s ability to deploy task-relevant strategy are likely to account for at least part of the executive resource requirements of visual memory tasks. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Adult age differences in temporal and item memory.

Three experiments tested whether the relationship between age differences in temporal and item memory depends on the degree to which the item memory measure relies on memory for context. The authors predicted a stronger relationship of temporal memory to free recall than to recognition memory. Results showed that age differences in temporal memory could be eliminated after controlling for free recall but not recognition memory performance. Under some conditions recognition memory accounted for a significant portion of age-related variance in temporal memory. These results challenge past research that has interpreted age differences in temporal and item memory as independent and suggest that a generalized decline in context memory may underlie reduced performance in older adults on all types of memory tests. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Similarities and differences between working memory and long-term memory: Evidence from the levels-of-processing span task.

Two experiments compared the effects of depth of processing on working memory (WM) and long-term memory (LTM) using a levels-of-processing (LOP) span task, a newly developed WM span procedure that involves processing to-be-remembered words based on their visual, phonological, or semantic characteristics. Depth of processing had minimal effect on WM tests, yet subsequent memory for the same items on delayed tests showed the typical benefits of semantic processing. Although the difference in LOP effects demonstrates a dissociation between WM and LTM, we also found that the retrieval practice provided by recalling words on the WM task benefited long-term retention, especially for words initially recalled from supraspan lists. The latter result is consistent with the hypothesis that WM span tasks involve retrieval from secondary memory, but the LOP dissociation suggests the processes engaged by WM and LTM tests may differ. Therefore, similarities and differences between WM and LTM depend on the extent to which retrieval from secondary memory is involved and whether there is a match (or mismatch) between initial processing and subsequent retrieval, consistent with transfer-appropriate-processing theory. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Growth in literacy and cognition in bilingual children at risk or not at risk for reading disabilities.

This study investigated growth in reading, vocabulary, and memory in children (ages 5 to 10) learning English as a second language identified at risk for reading disabilities (RD). A growth curve analysis showed that RD children were significantly below children not at risk in English and Spanish reading, Spanish short-term memory (STM), Spanish comprehension, and English and Spanish working memory (WM). RD children were also inferior on growth measures of English and Spanish WM and Spanish STM. Growth on measures of Spanish vocabulary, reading, STM, and WM accounted for 12% of the variance in predicting growth in English reading. However, only Spanish measures of WM growth contributed unique variance. The results show that growth in WM in the primary language predicts growth in second-language reading. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Impulsive decision making and working memory.

Decision making that favors short-term over long-term consequences of action, defined as impulsive or temporally myopic, may be related to individual differences in the executive functions of working memory (WM). In the first 2 experiments, participants made delay discounting (DD) judgments under different WM load conditions. In a 3rd experiment, participants high or low on standardized measures of impulsiveness and dysexecutive function were asked to make DD judgments. A final experiment examined WM load effects on DD when monetary rewards were real rather than hypothetical. The results showed that higher WM load led to greater discounting of delayed monetary rewards. Further, a strong direct relation was found between measures of impulsiveness, dysexecutive function, and discounting of delayed rewards. Thus, limits on WM function, either intrinsic or extrinsic, are predictive of a more impulsive decision-making style. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Explaining age differences in temporal working memory.

To determine the cognitive mechanisms underlying age differences in temporal working memory (WM), the authors examined the contributions of item memory, associative memory, simple order memory, and multiple item memory, using parallel versions of the delayed-matching-to-sample task. Older adults performed more poorly than younger adults on tests of temporal memory, but there were no age differences in nonassociative item memory, regardless of the amount of information to be learned. In contrast, a combination of associative and simple order memory, both of which were reduced in older adults, completely accounted for age-related declines in temporal memory. The authors conclude that 2 mechanisms may underlie age differences in temporal WM, namely, a generalized decline in associative ability and a specific difficulty with order information. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Working memory in mild Alzheimer's disease and early Parkinson's disease.

Alzheimer's disease (AD) and Parkinson's disease (PD) impair working memory (WM). It is unclear, however, whether the deficits seen early in the course of these diseases are similar. To address this issue, the authors compared the performance of 22 patients with mild AD, 20 patients with early PD and without dementia, and 112 control participants on tests of inhibition, short-term memory, and 2 commonly administered tests of WM. The results suggest that although mild AD and early PD both impair WM, the deficits may be related to the interruption of different processes that contribute to WM performance. Early PD disrupted inhibitory processes, whereas mild AD did not. The WM deficits seen in patients with AD may be secondary to deficits in other cognitive capacities, including semantic memory. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Text comprehension in Chinese children: Relative contribution of verbal working memory, pseudoword reading, rapid automated naming, and onset-rime phonological segmentation.

The present study examined the role of verbal working memory (memory span, tongue twister), 2-character Chinese pseudoword reading, rapid automatized naming (letters, numbers), and phonological segmentation (deletion of rimes and onsets) in inferential text comprehension in Chinese in 518 Chinese children in Hong Kong in Grades 3 to 5. It was hypothesized that verbal working memory, together with a small contribution from the other constructs, would explain individual variation in the children's text comprehension. Structural equation modeling and hierarchical multiple regression analyses generally upheld the hypotheses. Though Chinese pseudoword reading did not play an important mediating role in the effect of verbal working memory on text comprehension, verbal working memory had strong effects on pseudoword reading and text comprehension. The findings on the Chinese language support current Western literature as well as display the differential role of the constructs in Chinese reading comprehension. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Prefrontal Brain Magnetic Activity: Effects of Memory Task Demands.

Changes in spatiotemporal profiles of brain magnetic activity were investigated in healthy volunteers as a function of varying demands for phonological storage of spoken pseudowords. Greater activity for the phonological memory task was restricted to the dorsolateral prefrontal cortex (DLPFC) in the left hemisphere. During performance of the memory task, activity was initially found in the left superior temporal gyrus (between 100 and 200 ms), followed by activity in the ventrolateral prefrontal, motor, and premotor cortices (between 200 and 300 ms). Activity in DLPFCs was first observed consistently across participants later, between 300 and 400 ms. The data are consistent with the purported role of posterior temporal cortices in phonological analysis and in the online storage of phonological information, the contribution of ventrolateral and motor processing areas in establishment and short-term maintenance of articulatory representations through rehearsal, and the role of DLPFCs in the executive control of the maintenance operation. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Genetics of verbal working memory processes: A twin study of middle-aged men.

Genetic and environmental influences on cognitive components of reading span in 345 middle-aged male twin pairs were examined. Shared variance among word recognition (reading only), digits forward (short-term memory only), and reading span (concurrent reading plus memory) was almost entirely mediated by common genetic influences. Overall heritability was .52 for word recognition, .27 for digits forward, and .51 for reading span. All of the genetic influences on word recognition and digits forward, but only about one-half of the genetic influences on reading span, came from a common latent phenotype. The genetic influences that were specific to reading span were concluded to most likely reflect an executive function component. Implications for genetic studies of aging and prefrontal brain function are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)