Working memory capacity and aphasia.

The talk presents a capacity theory of syntactic comprehension disorders in aphasia. The work described was done in collaboration with Patricia Carpenter and Akira Miyake. The theory assumes that aphasic patients still possess the structural (syntactic) and procedural knowledge necessary to perform syntactic analysis, but that they suffer from reductions in working memory capacity for language. The theory explains how reductions in working memory capacity can lead to the pattern of comprehension breakdown observed in aphasic patients. According to a resource-reduction view of comprehension impairments in aphasia, patients are assumed to have intact structural and procedural knowledge to parse various sentences, but suffer from consequences of severely reduced working memory resources. Two types of experiments provide relevant supporting data. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The Relationship Between Age, Verbal Working Memory, and Language Comprehension.

A structural modeling approach was used to examine the relationships between age, verbal working memory (vWM), and 3 types of language measures: online syntactic processing, sentence comprehension, and text comprehension. The best-fit model for the online-processing measure revealed a direct effect of age on online sentence processing, but no effect mediated through vWM. The best-fit models for sentence and text comprehension included an effect of age mediated through vWM and no direct effect of age. These results indicate that the relationship among age, vWM, and comprehension differs depending on the measure of language processing and support the view that individual differences in vWM do not affect individuals' online syntactic processing. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

A capacity theory of comprehension: Individual differences in working memory.

A theory of the way working memory capacity constrains comprehension proposes that both processing and storage are mediated by activation and that the total amount of activation available in working memory varies among individuals. Individual differences in working memory capacity for language can account for qualitative and quantitative differences among college-age adults in several aspects of language comprehension. One aspect is syntactic modularity: The larger capacity of some individuals permits interaction among syntactic and pragmatic information, so that their syntactic processes are not informationally encapsulated. Another aspect is syntactic ambiguity: The larger capacity of some individuals permits them to maintain multiple interpretations. The theory is instantiated as a production system model in which the amount of activation available to the model affects how it adapts to the transient computational and storage demands that occur in comprehension. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Working memory and aphasia

This study investigated the relationship between working memory capacity and reading comprehension in aphasia. A measurement of working memory capacity was obtained using a modified version of Daneman and Carpenter's (1980) Reading Span Task. Sets of sentences ranging in length from one to six words were presented to 22 aphasic subjects who were required to retain the terminal words following each sentence for subsequent recognition. The maximum number of words retrieved was used as an index of working memory capacity. Two versions of the task (listening and reading) were presented depending on the subjects' ability to read. Strong positive correlations were found between working memory capacity, reading comprehension, and language function. These results support the notion that the ability of aphasic individuals to comprehend language is predictable from their working memory capacities.     

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)     

Children's Reading Comprehension Ability: Concurrent Prediction by Working Memory, Verbal Ability, and Component Skills.

The authors report data from a longitudinal study that addresses the relations between working memory capacity and reading comprehension skills in children aged 8, 9, and 11 years. At each time point, the authors assessed children's reading ability, vocabulary and verbal skills, performance on 2 working memory assessments (sentence-span and digit working memory), and component skills of comprehension. At each time point, working memory and component skills of comprehension (inference making, comprehension monitoring, story structure knowledge) predicted unique variance in reading comprehension after word reading ability and vocabulary and verbal ability controls. Further analyses revealed that the relations between reading comprehension and both inference making and comprehension monitoring were not wholly mediated by working memory. Rather, these component skills explained their own unique variance in reading comprehension. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The capacity theory of comprehension: new frontiers of evidence and arguments

A capacity theory of comprehension (M.A. Just & P.A. Carpenter, 1992) has provided an integrated account of several central aspects of sentence comprehension, such as the processing of syntactic ambiguity, complex embeddings, syntactic (non) modularity, and individual differences, in terms of the working-memory capacity for language. Some of the evidence supporting the theory is questioned by G.S. Waters and D. Caplan (1996a). This article identifies some of Waters and Caplan's errors about the empirical support in Just and Carpenter (1992), evaluates Waters and Caplan's alternative hypothesis, and presents the results of a new neuroimaging study that supports capacity theory and not Waters and Caplan's separate resources hypothesis.     

Individual Differences in the Inference of Word Meanings From Context: The Influence of Reading Comprehension, Vocabulary Knowledge, and Memory Capacity.

Two studies investigated the ability to use contextual information in stories to infer the meanings of novel vocabulary by 9-10-year-olds with good and poor reading comprehension. Across studies, children with poor reading comprehension were impaired when the processing demands of the task were greatest. In Study 2, working memory capacity was related to performance, but short-term memory span and memory for the literal content of the text were not. Children with poor reading comprehension were not impaired in learning novel vocabulary taught through direct instruction, but children with both weak reading comprehension and vocabulary were. Implications for the relation between vocabulary development and text comprehension are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Similarity-based interference during language comprehension: Evidence from eye tracking during reading.

The nature of working memory operation during complex sentence comprehension was studied by means of eye-tracking methodology. Readers had difficulty when the syntax of a sentence required them to hold 2 similar noun phrases (NPs) in working memory before syntactically and semantically integrating either of the NPs with a verb. In sentence structures that placed these NPs at the same linear distances from one another but allowed integration with a verb for 1 of the NPs, the comprehension difficulty was not seen. These results are interpreted as indicating that similarity-based interference occurs online during the comprehension of complex sentences and that the degree of memory accessibility conventionally associated with different types of NPs does not have a strong effect on sentence processing. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Development of adolescent reading comprehension in language 1 and language 2: A longitudinal analysis of constituent components.

This study investigated the relationship between reading comprehension development of 389 adolescents in their dominant language (Language 1 [L1], Dutch) and a foreign language (Language 2 [L2], English). In each consecutive year from Grades 8 through 10, a number of measurements were taken. Students' reading comprehension, their linguistic knowledge (vocabulary and grammar knowledge) and processing efficiency (speed of word recognition and sentence comprehension) in both languages, and their metacognitive knowledge about reading were assessed. The relative strengths of the effects of these components of reading were analyzed to distinguish among 3 hypotheses about the relationship between L1 and L2 reading comprehension: the transfer hypothesis, the threshold hypothesis, and the processing efficiency hypothesis. The transfer hypothesis predicts a strong relationship between L1 and L2 reading comprehension and a strong effect of metacognitive knowledge on L2 reading comprehension, whereas the threshold and processing efficiency hypotheses predict a more important role of language-specific knowledge and processing skills. Results support the transfer hypothesis, although language-specific knowledge and fluency also contribute to L2 reading performance. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Individual differences in working memory and comprehension: A test of four hypotheses.

A relationship has consistently been found between measures of working memory and reading comprehension. Four hypotheses for this relationship were tested in 3 experiments. In the 1st 2 experiments, a moving window procedure was used to present the operation–word and reading span tasks. High- and low-span Ss did not differentially trade off time on the elements of the tasks and the to-be-remembered word. Furthermore, the correlation between span and comprehension was undiminished when the viewing times were partialed out. Exp 3 compared a traditional experimenter-paced simple word-span and an S-paced span in their relationship with comprehension. The experimenter-paced word-span correlated with comprehension, but the S-paced span did not. The results of all 3 experiments support a general capacity explanation for the relationship between working memory and comprehension. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Development of the interplay between automatic processes and cognitive resources in reading.

An account was tested of the development of the interplay between automatic processes and cognitive resources in reading. According to compensatory-encoding theory, with advancing skill, readers increasingly keep automatic processes from faltering and provide timely, accurate data to working memory by pausing, looking back, rereading, and compensating in other ways when automatic processes fail. Reading skill profiles (e.g., word naming, semantic access, working memory capacity) were obtained from 71 third graders, 68 fifth graders, and 72 seventh graders from a university lab school or a public school (ages 7 to 15; 146 Caucasians, 61 African Americans, 2 Native Americans, 2 Latino Americans). Children participated in an unrestricted reading task (no time or performance pressure) and were randomly assigned to 1 of 2 levels of 3 experimental manipulations of restriction on reading: time pressure or no pressure, constant reading rate or variable reading rate, read silently or read aloud. Regression analyses revealed that developmental level and restriction moderated the reading skill level-comprehension relationship, and restriction lowered comprehension when it overwhelmed skills, especially for younger readers. Verbally inefficient readers compensated most often, and older readers compensated most efficiently. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effects of age, speed of processing, and working memory on comprehension of sentences with relative clauses.

Two hundred participants, 50 in each of four age ranges (19–29, 30–49, 50–69, 70–90) were tested for working memory, speed of processing, and the processing of sentences with relative clauses. In Experiment 1, participants read four sentence types (cleft subject, cleft object, subject-subject, subject-object) in a word-by-word, non-cumulative, self-paced reading task and made speeded plausibility judgments about them. In Experiment 2, participants read two types of sentences, one of which contained a doubly center embedded relative clause. Older participants' comprehension was less accurate and there was age-related slowing of online processing times in all but the simplest sentences, which increased in syntactically complex sentences in Experiment 1. This pattern suggests an age-related decrease in the efficiency of parsing and interpretation. Slower speed of processing and lower working memory were associated with longer online processing times only in Experiment 2, suggesting that task-related operations are related to general speed of processing and working memory. Lower working memory was not associated with longer reading times in more complex sentences, consistent with the view that general working memory is not critically involved in online syntactic processing. Longer online processing at the most demanding point in the most demanding sentence was associated with better comprehension, indicating that it reflects effective processing under some certain circumstances. However, the poorer comprehension performance of older individuals indicates that their slower online processing reflects inefficient processing even at these points. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

The anatomy of language revisited

The language areas have been classically viewed as a posterior, perceptual Wernicke's region connected with an anterior, motor Broca's area via a tract of long fibers denominated the arcuate fasciculus. Recent connectional studies in the monkey indicate that there may be few direct connections between the regions strictly corresponding to Broca's or Wernicke's areas, and that inferior parietal areas may serve as a link between them. The proposed connectional pattern of the language regions fits the network of parietotemporal-prefrontal connections that participate in working memory, a type of memory used in immediate cognitive processing. Supporting this concept, brain activation studies in the human during linguistic working memory tasks have determined a close relation between the supramarginal gyrus (parietal area 40) and Broca's area. We suggest that language processing is closely related to working memory networks, and that the language regions in fact originated in evolution from a working memory network for linguistic utterances.     

Listening in aging adults: From discourse comprehension to psychoacoustics.

Older adults, with or without clinical hearing loss, have more trouble than younger people understanding speech in everyday life. These age-related difficulties in speech understanding may be attributed to changes in higher-level cognitive processes such as language comprehension, memory, attention, and cognitive slowing, or to lower-level sensory and perceptual processes. A complicating factor in determining how these sources might contribute to age-related declines in speech understanding is that they are highly correlated. This study describes attempts to systematically investigate sensory-cognitive interactions in controlled experimental situations. The authors looked at experimental conditions that closely approximate everyday listening, and show that older adults do indeed experience deficits in spoken language comprehension relative to younger adults in these conditions. Finally, further experiments designed to isolate more precisely the cognitive and perceptual sources of these age-related differences and how they vary with listening condition are reviewed. In large part, it was found that age-related changes in speech understanding are a consequence of auditory declines. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Beyond pictures and words: Alternative information-processing models for imagery effect in verbal memory.

Presents an information-processing approach to imagery effects in verbal memory tasks. A general model of the process of forming images from verbal input is developed, based on propositional memory representations like those used in computer simulations of sentence comprehension, visual scene analysis, and image processing. The general model is then refined in several classes of alternative models that attempt to account for imagery effects, with emphasis on sentence memory results, by using different mechanisms in the general model. The major division in the alternative models is whether the facilitation produced by imagery is due to the actual storage of image information or is just a by-product of image formation or the use of high-imagery materials. Some of the models are rejected on the basis of published data. Two of the remaining models would require substantial progress in the study of sentence memory and comprehension in a way not directly related to imagery. The models most likely to be successful are those that assume that the use of imagery results in the storage of redundant information that provides alternate retrieval routes. (2 p ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Number Skills and Knowledge in Children With Specific Language Impairment.

The number skills of groups of 7- to 9-year-old children with specific language impairment (SLI) attending mainstream or special schools were compared with an age and nonverbal reasoning matched group (age control [AC]) and with a younger group matched on oral language comprehension. The SLI groups performed below the AC group on every skill. They also showed lower working memory functioning and had received lower levels of instruction. Nonverbal reasoning, working memory functioning, language comprehension, and instruction accounted for individual variation in number skills to differing extents depending on the skill. These factors did not explain the differences between SLI and AC groups on most skills. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

Externalizing psychopathology and behavioral disinhibition: Working memory mediates signal discriminability and reinforcement moderates response bias in approach–avoidance learning.

Research has suggested that reduced working memory capacity plays a key role in disinhibited patterns of behavior associated with externalizing psychopathology. In this study, participants (N = 365) completed 2 versions of a go/no-go mixed-incentive learning task that differed in the relative frequency of monetary rewards and punishments for correct and incorrect active-approach responses, respectively. Using separate structural equation models for conventional (hit and false alarm rates) and signal detection theory (signal discriminability and response bias) performance indices, distinct roles for working memory capacity and changes in payoff structure were found. Specifically, results showed that (a) working memory capacity mediated the effects of externalizing psychopathology on false alarms and discriminability of go versus no-go signals; (b) these effects were not moderated by the relative frequency of monetary rewards and punishments; (c) the relative frequency of monetary rewards and punishments moderated the effects of externalizing psychopathology on hits and response bias for go versus no-go responses; and (d) these effects were not mediated by working memory capacity. The findings implicate distinct roles for reduced working memory capacity and poorly modulated active approach and passive avoidance in the link between externalizing psychopathology and behavioral disinhibition. (PsycINFO Database Record (c) 2011 APA, all rights reserved)