Limited Working Memory Research Articles

Working Memory: A Cognitive Limit to Non-Human Primate Recursive Thinking Prior to Hominid Evolution

In this paper I explore the possibility that recursion is not part of the cognitive repertoire of non-human primates such as chimpanzees due to limited working memory capacity. Multiple lines of data, from nut cracking to the velocity and duration of cognitive development, imply that chimpanzees have a short-term memory size that limits working memory to dealing with two, or at most three, concepts at a time. If so, as a species they lack the cognitive capacity for recursive thinking to be integrated into systems of social organization and communication. If this limited working memory capacity is projected back to a common ancestor for Pan and Homo, it follows that early hominid ancestors would have had limited working memory capacity. Hence we should find evidence for expansion of working memory capacity during hominid evolution reflected in changes in the products of conceptually framed activities such as stone tool production. Data on the artifacts made by our hominid ancestors support this expansion hypothesis for hominid working memory, thereby leading to qualitative differences between Pan and Homo.

Conceptual knowledge increases infants' memory capacity

Adults can expand their limited working memory capacity by using stored conceptual knowledge to chunk items into interrelated units. For example, adults are better at remembering the letter string PBSBBCCNN after parsing it into three smaller units: the television acronyms PBS, BBC, and CNN. Is this chunking a learned strategy acquired through instruction? We explored the origins of this ability by asking whether untrained infants can use conceptual knowledge to increase memory. In the absence of any grouping cues, 14-month-old infants can track only three hidden objects at once, demonstrating the standard limit of working memory. In four experiments we show that infants can surpass this limit when given perceptual, conceptual, linguistic, or spatial cues to parse larger arrays into smaller units that are more efficiently stored in memory. This work offers evidence of memory expansion based on conceptual knowledge in untrained, preverbal subjects. Our findings demonstrate that without instruction, and in the absence of robust language, a fundamental memory computation is available throughout the lifespan, years before the development of explicit metamemorial strategies.

Selecting learning tasks: Effects of adaptation and shared control on learning efficiency and task involvement

Complex skill acquisition by performing authentic learning tasks is constrained by limited working memory capacity [Baddeley, A. D. (1992). Working memory. Science, 255, 556–559]. To prevent cognitive overload, task difficulty and support of each newly selected learning task can be adapted to the learner’s competence level and perceived task load, either by some external agent, the learner herself, or both. Health sciences students ( N = 55) participated in a study using a 2 × 2 factorial design with the factors adaptation (present or absent) and control over task-selection (program control or shared control). As hypothesized, adaptation led to more efficient learning; that is, higher learning outcomes combined with less effort invested in performing the learning tasks. Shared control over task-selection led to higher task involvement, that is, higher learning outcomes combined with more effort directly invested in learning. Adaptation also produced greater task involvement.

Interactions between divided attention and working-memory load in patients with severe traumatic brain injury

The aim of this study was to assess the relationships between divided-attention deficits and working-memory limitations after severe traumatic brain injury (TBI). Severe TBI patients (n = 43) and controls were given a n-back task of three different load levels, which was performed as a single and a dual task. Patients demonstrated, as expected, a difficulty in dual-task processing and an increased susceptibility to high working-memory load, but dual-task performance and working-memory load did not interact as expected. These results are in accordance with recent findings suggesting that dual-task performance and other working-memory functions represent dissociable although interrelated abilities.

Children with specific language impairment: an investigation of their narratives and memory

Narratives have been used by a number of researchers to investigate the language of children with specific language impairment (SLI). While a number of explanations for SLI have been proposed, there is now mounting evidence that children with SLI have limited memory resources. Phonological memory has been the focus of the research on memory with this population. However, the use of narrative tasks to investigate memory limitations in SLI has not previously been undertaken. The aims of the research were to investigate the narrative and memory abilities of 6-year-old children with SLI and the association between narrative skills and memory. Two studies were conducted. In Study 1 the performance of the children with SLI was compared with that of their peers with typical language development (AM), and to that of a younger group (LM) matched on expressive language (about 2 years younger). Children were asked to recall ('story recall') and show comprehension of a narrative they had been told, and also to tell a story based on a series of pictures ('story generation'), to recall their story and to answer comprehension questions about it. In Study 2 the children with SLI from Study 1 and the AM children from Study 1 were tested on four working memory tasks: word and digit span, the Recalling Sentences task from the Clinical Evaluation of Language Fundamentals--Third Edition, and a dual-processing task. An inhibition task and an attention task were also included. It was predicted that children with SLI would perform more poorly than the AM group on measures of narrative telling, but comparably with the LM group. It was also predicted that the SLI group would perform more poorly than the AM group on both literal and inferencing comprehension questions but comparably with the LM group. The third prediction was that there would be significant associations between children's performance on the narrative tasks and the tasks measuring working memory. In Study 1 the children with SLI performed more like the younger group on recall of a narrative they had heard, but more like their peers when asked to generate and recall their own narrative based on a series of pictures. The children with SLI had difficulty with inferencing questions. In Study 2 the impaired group performed significantly worse on measures of memory, showing a lower working memory capacity. The children with SLI made more errors on the attention task, but no group differences were found on the inhibition task. In comparing results from Studies 1 and 2, significant correlations were found between performance on the narrative tasks and memory tasks, but the contribution of memory to the narrative task scores differed for the two stories. The Recalling Sentences memory task was found to be the best overall measure for predicting variance on story comprehension and recall. In support of previous research, the children with SLI showed problems with inferencing, linking directly observed or stated information to likely outcomes. They also showed a limited working memory capacity, and they were more likely to make errors in attention. A main finding was that the narrative abilities of the 6-year-old children were linked to their verbal working memory. The information the SLI group heard was harder to access than information they had been able to generate themselves based on a series of pictures. The findings suggest that children with SLI are likely to be at a disadvantage in classroom situations, particularly for information presented aurally and if the information is complex. The use of pictorial aids may help them encode the information. They would also benefit from having information broken into manageable units.

Developmental Stages in Advanced SLA

AbstractSecond Language Acquisition (SLA) researchers have yet to map the developmental stages language learners go through as they approach the target language. In studies of English as a Second Language (ESL) writing, the term 'advanced learner' has been applied indiscriminately to learners ranging from freshman ESL composition to graduate students. There is a need to examine the advanced stages of SLA in order to refine SLA theories and pedagogical approaches. A corpus of texts written by non-native English-speaking doctoral students in applied linguistics from several linguistic backgrounds was analyzed to determine the texts’ lexical, morphological and syntactic fluency, accuracy and complexity. A sub-corpus of papers by native-English-speaking peers was used for comparison. The texts were strictly-timed and loosely-timed exams written 2 to 3 years apart. Surveys and interviews were also conducted. Based on findings, the study defines data-based criteria that distinguish four quantitatively and qualitatively distinct developmental stages: the advanced, highly advanced, near-native, and native-like stages. Advanced learners make more frequent and varied errors which can be explained by transfer from the first language. Native-like writers make few errors that can be explained by overgeneralization of conventions from informal English and working memory limitations (similar to native speakers’ errors). The study suggests that SLA is a process of transfer followed by relearning of morpho-syntactic specifications (Herschensohn, 2000), with syntax being used with the greatest accuracy (Bardovi-Harlig & Bofman, 1989) and lexicon with the least. The relationships between accuracy and other social and cognitive factors are considered, and pedagogical recommendations are made.

Developmental Stages in Advanced SLA

Second Language Acquisition (SLA) researchers have yet to map the developmental stages language learners go through as they approach the target language. In studies of English as a Second Language (ESL) writing, the term 'advanced learner' has been applied indiscriminately to learners ranging from freshman ESL composition to graduate students. There is a need to examine the advanced stages of SLA in order to refine SLA theories and pedagogical approaches. A corpus of texts written by non-native English-speaking doctoral students in applied linguistics from several linguistic backgrounds was analyzed to determine the texts’ lexical, morphological and syntactic fluency, accuracy and complexity. A sub-corpus of papers by native-English-speaking peers was used for comparison. The texts were strictly-timed and loosely-timed exams written 2 to 3 years apart. Surveys and interviews were also conducted. Based on findings, the study defines data-based criteria that distinguish four quantitatively and qualitatively distinct developmental stages: the advanced, highly advanced, near-native, and native-like stages. Advanced learners make more frequent and varied errors which can be explained by transfer from the first language. Native-like writers make few errors that can be explained by overgeneralization of conventions from informal English and working memory limitations (similar to native speakers’ errors). The study suggests that SLA is a process of transfer followed by relearning of morpho-syntactic specifications (Herschensohn, 2000), with syntax being used with the greatest accuracy (Bardovi-Harlig & Bofman, 1989) and lexicon with the least. The relationships between accuracy and other social and cognitive factors are considered, and pedagogical recommendations are made.

A methodological contribution to the assessment of nonword repetition—a comparison between children with specific language impairment and hearing-impaired children with hearing aids or cochlear implants

Poor nonword repetition is considered as a clinical marker of specific language impairment (SLI). In children with expressive language problems, the analysis and scoring procedures are often insufficiently described. We argue for a combined analysis of segmental and suprasegmental accuracy in nonword repetition tasks as well as an appreciation of gender differences. The view is taken based on empirical findings in a comparison between children with specific language impairment, children with mild/moderate hearing impairment and hearing aids (HI), and children with severe to profound hearing impairment with cochlear implants (CI). With age and gender taken into consideration, the main effects of both group and syllable level on a combined measure of segmental and suprasegmental accuracy remained. Although not necessarily an index of limited working memory capacity, persistently poor imitation of nonwords might be an indication of language impairment in children with mild/moderate HI and in children with CI.

Pre‐schoolers’ feature placement on own and others’ person drawings

Young children find meaning in the drawings they create that may not be apparent to an adult observer. The purpose of this study is to access the children’s views using a drawing change task. Seventy‐three pre‐schoolers were asked to draw a person and then draw a person with a belly button. It was anticipated that tadpole (no separate body) drawers would include a body to accommodate this new feature. Instead belly buttons were included without modifications to the figure suggesting that in the children’s view tadpole figures are not as deficient as they might appear. When placing a belly button on a figure drawn by someone else 40% of tadpole drawers responded differently compared to their own. Possible explanations considered are the effect of active involvement in creating a drawing, the respect for another’s drawing intention, and lack of awareness of differences due to working memory limitations.

As far as individuals with conduction aphasia understood these sentences were ungrammatical: Garden path in conduction aphasia

Background: Recent studies have indicated that working memory is not a unitary resource and that different types of working memory are used for different types of linguistic processing: syntactic, semantic, and phonological. Phonological working memory was found to support the comprehension of sentences that require re‐access to the word‐form of a word that appeared earlier in the sentence. The research was supported by a research grant from the National Institute for Psychobiology in Israel (Friedmann 2004‐5‐2b), and by the Joint German–Israeli Research Program grant (Friedmann GR‐01791). We thank Irena Botwinik‐Rotem, Tali Siloni, and Michal Biran for discussions of this study. Aims: This study explored the relation between phonological working memory and sentence comprehension by testing the comprehension of garden path sentences in individuals with conduction aphasia who have very limited phonological working memory. Our prediction was that if phonological working memory limitation hampers word‐form reactivation, only the comprehension of garden paths that require word‐form reactivation will be impaired, whereas garden paths that require only structural reanalysis will be better preserved. Methods & Procedures: Five individuals with conduction aphasia and 15 matched controls participated in working memory tests and a garden path comprehension test. The phonological working memory assessment included a battery of 10 tests, which showed that four of the individuals, who had input conduction aphasia, had very limited phonological working memory, and one individual, with output conduction aphasia, had unimpaired working memory. The comprehension study included 60 garden path sentences of three types: structural garden paths, which require only structural reanalysis, lexical garden paths, which require lexical re‐access in addition to structural reanalysis, and optional‐complement garden paths, which require re‐access to the lexical‐syntactic frame of the verb in addition to the structural reanalysis. Outcomes & Results: The main result was that the individuals with input conduction aphasia showed different degrees of impairment in different types of garden path sentences. The lexical garden paths were exceptionally hard for them, with a mere 10% correct, and significantly more difficult than the structural garden paths. The individual with output conduction aphasia whose working memory was intact comprehended the lexical garden paths similarly to the normal controls. Conclusions: These findings indicate that phonological working memory impairment only affects the comprehension of sentences that require phonological, word‐form re‐access. The type of sentence and the type of processing it requires should be taken into account when trying to predict the effect of working memory limitation on a patient's ability to understand sentences. Whereas individuals with input conduction aphasia can understand complex syntactic structures well, they have considerable difficulties understanding sentences that also require re‐access to a word‐form.

Evidence for disruption in prefrontal cortical functions in juvenile bipolar disorder

Systematic parsing of executive function processes is critical for the development of more specific models of neurobiological processes mediating disturbed cognition in youth with bipolar disorder (BPD). A sample of 33 children and adolescents with bipolar I disorder (BPD I) (mean age 12.1 +/- 3.0 years, 39% female) and 44 demographically matched healthy participants (mean age 12.9 +/- 2.8 years, 50% female) completed a neurocognitive battery including measures aimed at detection of disruption in prefrontal cortical circuitry (i.e., working memory, set shifting, and rule attainment). Compared to healthy controls, BPD I children exhibited significant deficits in spatial working memory, visual sequencing and scanning, verbal fluency and abstract problem solving, particularly when a memory component was involved. In our spatial delayed response task, memory set size was parametrically varied; the performance pattern in BPD I children suggested deficits in short-term memory encoding and/or storage, rather than capacity limitations in spatial working memory. Earlier age at onset of illness and antipsychotic medication usage were associated with poorer performance on speeded information-processing tasks; however, severity of mood symptomatology and comorbidity with disruptive behavior disorders were not associated with task performance. These results suggest impairment in measures of prefrontal cortical function in juvenile BPD I that are similar to those seen in the adult form of the illness, and implicate both the ventral and dorsolateral prefrontal cortex as loci of pathology in juvenile BPD. As these deficits were not associated with clinical state or comorbidity with other disorders, they may reflect trait-related impairments, a hypothesis that will be pursued further in longitudinal studies.

Working memory limitations in children with severe language impairment

In the present study, the relations of various aspects of working memory to various aspects of language problems in a clinical sample of 97 Dutch speaking 5-year-old children with severe language problems were studied. The working memory and language abilities of the children were examined using an extensive battery of tests. Working memory was operationalized according to the model of Baddeley. Confirmative factor analyses revealed three memory factors: phonological, visual and central executive. Language was construed as a multifactorial construct, and confirmative factor analyses revealed four factors: lexical-semantic abilities, phonological abilities, syntactic abilities and speech production abilities. Moderate to high correlations were found between the memory and language factors. Structural equation modelling was used to further explore the relations between the different factors. Phonological memory was found to predict phonological abilities; central-executive memory predicted lexical-semantic abilities; and visual memory predicted speech production abilities. Phonological abilities also predicted syntactic abilities. Both the theoretical and clinical implications of the findings are discussed. Learning outcomes: The reader will be introduced to the concepts of multifactorial components of working memory as well as language impairment. Secondly the reader will recognize that working memory and language impairment factors can be related. Particular emphasis will be placed on phonological memory, central-executive memory and visual memory and their possible prediction of specific components of language impairment.

Tapping to a Very Slow Beat: A Comparison of Musicians and Nonmusicians

WHEN NONMUSICIANS TAP with isochronous auditory tone sequences, the taps typically precede the tone onsets. However, when the tone inter-onset interval (IOI) is increased beyond 2 s, an increasing proportion of taps follows the tone onsets by 150 ms or more. Such responses indicate reactions rather than anticipations, and they have been interpreted as reflecting a rate limit of synchronization related to a temporal limit of auditory working memory. In the present study, musicians and nonmusicians were asked to synchronize their taps with sequences whose IOIs ranged from 1000 to 3500 ms. Nonmusicians showed much larger anticipation errors and higher variability but actually fewer reactive responses than musicians. No clear landmarks of a rate limit for synchronization were observed.

The impact of working memory limitations on the design process during conceptualization

This paper presents the cognitive activity differences of six expert architects when they design in blindfolded (BF) and sketching (SK) conditions. It was observed that all participants' overall cognitive activity and perceptual activity in the BF sessions dropped below their activity in the SK sessions, approximately after 20 min during the timeline of their design activity. This drop in performance can be explained by higher cognitive demands under BF conditions. In the absence of sketching, architects may experience an overload of visuo-spatial working memory (VSWM). We also tested whether this may have an impact on the linking of their design ideas. We previously reported that the intensity and the information content (entropy) of the idea development were not influenced by VSWM load. The reach of idea links was found to be smaller in the second half of the BF design sessions. Working memory limitations had an impact only on the reach of idea links. We discuss whether these differences are dependent on working memory limitations or idea saturation during conceptual designing.

The directed attention model of infant social cognition

During infancy, humans have a limited attention span, a limited working memory and an initial lack of social experience. Given these constraints, why are infants so socially competent and how are they capable of processing such complex social information? Here we present an information-processing hypothesis that may account for these early social capacities. We outline those aspects of the social situation that must be processed for the infant to respond in a socially appropriate manner. We also outline potential cognitive sequences through which this information is processed. We conclude that the infant uses social information to determine what is relevant in the environment and in doing so, the infant uses each successive aspect of the social world to filter the overall amount of available information to a manageable size.

Maintaining the ties that bind: The role of an intermediate visual memory store in the persistence of awareness

Segregation and feature binding are essential to the perception and awareness of objects in a visual scene. When a fragmented line-drawing of an object moves relative to a background of randomly oriented lines, the previously hidden object is segregated from the background and consequently enters awareness. Interestingly, in such shape-from-motion displays, the percept of the object persists briefly when the motion stops, suggesting that the segregated and bound representation of the object is maintained in awareness. Here, we tested whether this persistence effect is mediated by capacity-limited working-memory processes, or by the amount of object-related information available. The experiments demonstrate that persistence is affected mainly by the proportion of object information available and is independent of working-memory limits. We suggest that this persistence effect can be seen as evidence for an intermediate, form-based memory store mediating between sensory and working memory.

Spared place and object-place learning but limited spatial working memory capacity in rats with selective lesions of the dentate gyrus

We studied the cognitive performance of rats with colchicine-induced lesions of the hippocampal dentate gyrus (DG) on a range of spatial, non-spatial and mixed spatial/procedural tasks. Rats were assigned to three experimental groups receiving large colchicine lesions (7 μg per hippocampus), small colchicine lesions (1.75 μg per hippocampus) or sham lesions. Stereological estimates of cell density indicated that the colchicine treatments induced dose-dependent damage to the DG, while sparing in large part other hippocampal subfields. Remarkably, the behavioural results showed that the colchicine lesions did not affect the performance of rats in an object discrimination task, in an object-place associative task in which a familiar object was displaced from a given position nor in a spontaneous spatial discrimination task performed in the T-maze. However, rats in both lesion groups were severely impaired in a reinforced non-matching-to-position working memory task conducted in the T-maze. Importantly, performance in the working memory task correlated strongly with cell density in the DG but not with cell density in the CA1 and CA3 areas. Only rats with large-lesions showed a transient deficit in a reinforced rule-based conditional discrimination task. These data demonstrated that rats with selective lesions of the DG readily acquire and retain neural representations relative to objects and places but are specifically impaired in their ability to update rapidly and flexibly spatial information that is essential to guide goal-directed actions.

Antecedent Priming at Trace Positions in Children’s Sentence Processing

The present study examines whether children reactivate a moved constituent at its gap position and how children’s more limited working memory span affects the way they process filler-gap dependencies. 46 5–7 year-old children and 54 adult controls participated in a cross-modal picture priming experiment and underwent a standardized working memory test. The results revealed a statistically significant interaction between the participants’ working memory span and antecedent reactivation: High-span children (n = 19) and high-span adults (n = 22) showed evidence of antecedent priming at the gap site, while for low-span children and adults, there was no such effect. The antecedent priming effect in the high-span participants indicates that in both children and adults, dislocated arguments access their antecedents at gap positions. The absence of an antecedent reactivation effect in the low-span participants could mean that these participants required more time to integrate the dislocated constituent and reactivated the filler later during the sentence.

INHIBITION CONTROL AND WORKING MEMORY CAPACITY IN CHILDREN WITH SLI

This study examined the "inefficient inhibition hypothesis" (IIH; Bjorklund & Harnishfeger, 1990; Wilson & Kipp, 1998) in three groups: children with specific language impairment (SLI), age-matched and language-matched controls. The IIH suggests that individuals with efficient inhibition skills perform better on working memory tasks because they are able to keep out irrelevant information from working memory. Children with SLI show processing capacity limitations. This study examined whether the working memory limitations are impacted by inhibition problems in this population. Working memory capacity was measured with a listening span task and children's inhibition errors were categorized. These errors reflected either immediate or delayed inhibition problems and they indicated either contextual distractions or perseverations. Children with SLI produced more inhibition errors than their peers in most categories. The results show an association between inhibition control and working memory capacity, but the direction of causality is not clear.

The nature of individual differences in working memory capacity: Active maintenance in primary memory and controlled search from secondary memory.

Studies examining individual differences in working memory capacity have suggested that individuals with low working memory capacities demonstrate impaired performance on a variety of attention and memory tasks compared with individuals with high working memory capacities. This working memory limitation can be conceived of as arising from 2 components: a dynamic attention component (primary memory) and a probabilistic cue-dependent search component (secondary memory). This framework is used to examine previous individual differences studies of working memory capacity, and new evidence is examined on the basis of predictions of the framework to performance on immediate free recall. It is suggested that individual differences in working memory capacity are partially due to the ability to maintain information accessible in primary memory and the ability to search for information from secondary memory.