Limited Working Memory Research Articles

Markov-chain model and algorithmic procedure for the performance analysis of closed cyclic queues

This paper presents a model and an algorithmic procedure to analyze closed cyclic queues that are subject to blocking. We consider the first two moments of the processing time and present the fitting of phase-type distributions such that the number of phases and transitions is minimal. Using phase-type distributions, we enable the analysis of queueing systems with processing times with any coefficient of variation. We model the closed cyclic queues subject to blocking as continuous-time Markov chains. The implementation procedure covers the state-space generation and the determination of the infinitesimal generator matrix. Apart from rounding errors, we obtain exact results for the queueing model this way. The results are useful as reference values for the output of approximate approaches. Further, the algorithmic procedure enables a repeated analysis of different configuration alternatives as needed in optimization procedures. Though the method is very fast for small cyclic queues, it takes a long computation time for larger systems. Furthermore, the size of the queueing model to be analyzed is restricted due to the limited working memory with its present-day capacity. In a numerical study, the computation times for different configurations are investigated, limits in the size of the applicable queueing model are given, and numerical results of the performance measures are provided.

Self-instructional module based on cognitive load theory: a study on information retention among trainee teachers

The aim of the research is to study the information retention among trainee teachers using a self-instructional printed module based on Cognitive Load Theory for learning spreadsheet software. Effective pedagogical considerations integrating the theoretical concepts related to cognitive load are reflected in the design and development of the module. As working memory limitations affect knowledge acquisition, instructions should be designed with the aim of reducing any unnecessary cognitive load. Repeated measures Analysis of Variance was conducted on 36 trainee teachers working on the developed module, and the results showed no effect on information retention. However, recorded performance scores were high and sustained throughout the post-activities, indicating that trainees may have demonstrated better retention skills. Generally, the results provide some evidence that modifications to the design of the instructions are necessary to improve the module so as to produce trainees with a deeper comprehension and better retention of Information and Communication Technology knowledge and skills.

Ambiguity in Mind: Modeling Working-Memory Limits and Belief Quantization Under Uncertainty

Much of the ambiguity that economic decision makers face may stem from scarce cognitive resources, such as limits on working-memory capacity. This paper constructs a simple model of bounded judgment based on the idea that an agent’s maximum working-memory capacity is limited in two dimensions: any bounded agent faces limits on both the 1) number and 2) sizes of units of evidence that she can hold in mind at once when generating subjective beliefs. It is shown how this two-dimensional limit on working-memory capacity tends to cause ambiguity in the minds of bounded agents, and that, to cope with this mental ambiguity, bounded agents almost always distort their beliefs. These distortions are representable by quantization functions, which restrict bounded agents’ subjective beliefs to a finite, context-dependent subset of values along the unit interval (i.e., beliefs are ‘quantized’). Modeling belief distortions and ambiguity through quantization allows a unified explanation of several anomalous phenomena in choice that does not require agents to have any complicated preferences; these anomalies include: the Ellsberg paradox, hard-easy effects, and description-experience gaps. Finally, it is shown how working-memory limits and salience can help agents to rapidly spot patterns.

Brain responses to syntax constrained by time-driven implicit prosodic phrases

Abstract Previous research suggests that time-based working memory limits of 2–3 s constrain the integration of verbal information, and that speakers tend to parse sentences into prosodic phrases that do not extend beyond this time window. The present study used Event-Related Potentials (ERPs) to investigate how time-driven implicit prosodic phrasing influences the syntactic processing of embedded clauses. Participants read Swedish sentences in which the first embedded clause had a subordinate, main or neutral clause structure cued by the position of the sentence adverb. The presentation rate was manipulated so that either one or two clauses were read within 2.7 s. When the 2.7 s time limit was reached before the onset of the embedded clause, the sentence adverb indicating subordinate clause structure elicited a posterior negativity and a late positivity. These effects were interpreted to reflect the detection of unexpected word order, followed by the revision of the anticipated main clause structure. A positive shift that correlated with individual working memory span was also seen at the clause-final word after 2.7 s, possibly indicating closure of an implicit prosodic phrase. These results suggest that prosodic phrasing was influenced by time-based working memory limits, which in turn affected syntactic analysis: readers were more likely to interpret an embedded clause as a main clause if it could be associated with the beginning of a new prosodic phrase.

Speed Matters: Relationship between Speed of Eye Movements and Modification of Aversive Autobiographical Memories.

Eye movement desensitization and reprocessing (EMDR) is an efficacious treatment for post-traumatic stress disorder. In EMDR, patients recall a distressing memory and simultaneously make eye movements (EM). Both tasks are considered to require limited working memory (WM) resources. Because this leaves fewer resources available for memory retrieval, the memory should become less vivid and less emotional during future recall. In EMDR analogue studies, a standardized procedure has been used, in which participants receive the same dual task manipulation of 1 EM cycle per second (1 Hz). From a WM perspective, the WM taxation of the dual task might be titrated to the WM taxation of the memory image. We hypothesized that highly vivid images are more affected by high WM taxation and less vivid images are more affected by low WM taxation. In study 1, 34 participants performed a reaction time task, and rated image vividness, and difficulty of retrieving an image, during five speeds of EM and no EM. Both a high WM taxing frequency (fast EM; 1.2 Hz) and a low WM taxing frequency (slow EM; 0.8 Hz) were selected. In study 2, 72 participants recalled three highly vivid aversive autobiographical memory images (n = 36) or three less vivid images (n = 36) under each of three conditions: recall + fast EM, recall + slow EM, or recall only. Multi-level modeling revealed a consistent pattern for all outcome measures: recall + fast EM led to less emotional, less vivid and more difficult to retrieve images than recall + slow EM and recall only, and the effects of recall + slow EM felt consistently in between the effects of recall + fast EM and recall only, but only differed significantly from recall + fast EM. Crucially, image vividness did not interact with condition on the decrease of emotionality over time, which was inconsistent with the prediction. Implications for understanding the mechanisms of action in memory modification and directions for future research are discussed.

PD19-11 SURGEON PERFORMANCE AND DISTRACTIONS IN THE OPERATING ROOM: A RANDOMIZED, CONTROLLED, CROSSOVER TRIAL

You have accessJournal of UrologyTechnology & Instruments: Surgical Education & Skills Assessment III1 Apr 2015PD19-11 SURGEON PERFORMANCE AND DISTRACTIONS IN THE OPERATING ROOM: A RANDOMIZED, CONTROLLED, CROSSOVER TRIAL Ryan Speir, Timothy Brand, and Richard Greene Ryan SpeirRyan Speir More articles by this author , Timothy BrandTimothy Brand More articles by this author , and Richard GreeneRichard Greene More articles by this author View All Author Informationhttps://doi.org/10.1016/j.juro.2015.02.710AboutPDF ToolsAdd to favoritesDownload CitationsTrack CitationsPermissionsReprints ShareFacebookTwitterLinked InEmail INTRODUCTION AND OBJECTIVES Surgery is a complex interaction of cognitive and psychomotor skills that requires significant concentration to perform safely. The ability to maintain focus amidst the many distractions in the operating room (O.R.) is largely influenced by effective allocation of limited working memory resources. Distractions can overload working memory resources resulting in diminished performance. We hypothesize that O.R. distractions are significant and negatively impact surgeon performance. METHODS We conducted a prospective randomized controlled trial with ten resident and ten attending surgeons. Participants were required to meet proficiency benchmarks on the previously validated high fidelity virtual reality daVinci desktop simulator (dV Trainer, Mimic Technologies, Seattle WA) to minimize performance variability. Participants performed four simulated surgical tasks with increasing complexity on the dV Trainer. Participants performed each task four times in a cross-over design; twice with distraction (intervention) and twice without distraction (control). Distraction was provided by 85 decibels of background operating room noise and board-style medical questions. Surgical performance was then determined by total task time, economy of motion (EOM) and master work space range (MWSR). Data were analyzed using SPSS. RESULTS Distraction had a detrimental effect on surgeon performance. During the simpler tasks, pick and place jacks (PAPJ) and ring walk (RW), attending surgeons performance declined with distraction in EOM (175.41 vs 189.29, p=0.014) and MWSR (8.61 vs 9.51, p=0.02), respectively. Resident performance was not affected by distraction in the PAPJ and RW tasks for each metric, but on more difficult tasks like pegboard level 1, resident surgeons showed significant decline due to distraction on both EOM (447.1 vs 485.65, p=0.03) and MWSR (9.48 vs 10.59, p=0.007). On the most advanced task, pegboard level 3, neither group significantly declined however experts EOM (787.33 vs 757.13) and MWSR (13.15 vs 11.99) was superior. CONCLUSIONS We have shown that distractions during VR robotic task performance can adversely affect surgeon performance. Resident surgeons seem to be more affected by distraction as the complexity of task increases. With increasing complexity of tasks, attending surgeons were less affected by distraction. The results indicate the need to further examine the detrimental effect distractions have on surgical performance. © 2015 by American Urological Association Education and Research, Inc.FiguresReferencesRelatedDetails Volume 193Issue 4SApril 2015Page: e396 Advertisement Copyright & Permissions© 2015 by American Urological Association Education and Research, Inc.MetricsAuthor Information Ryan Speir More articles by this author Timothy Brand More articles by this author Richard Greene More articles by this author Expand All Advertisement Advertisement PDF DownloadLoading ...

Real-time state estimation in a flight simulator using fNIRS.

Working memory is a key executive function for flying an aircraft. This function is particularly critical when pilots have to recall series of air traffic control instructions. However, working memory limitations may jeopardize flight safety. Since the functional near-infrared spectroscopy (fNIRS) method seems promising for assessing working memory load, our objective is to implement an on-line fNIRS-based inference system that integrates two complementary estimators. The first estimator is a real-time state estimation MACD-based algorithm dedicated to identifying the pilot’s instantaneous mental state (not-on-task vs. on-task). It does not require a calibration process to perform its estimation. The second estimator is an on-line SVM-based classifier that is able to discriminate task difficulty (low working memory load vs. high working memory load). These two estimators were tested with 19 pilots who were placed in a realistic flight simulator and were asked to recall air traffic control instructions. We found that the estimated pilot’s mental state matched significantly better than chance with the pilot’s real state (62% global accuracy, 58% specificity, and 72% sensitivity). The second estimator, dedicated to assessing single trial working memory loads, led to 80% classification accuracy, 72% specificity, and 89% sensitivity. These two estimators establish reusable blocks for further fNIRS-based passive brain computer interface development.

Older Adults’ Comprehension of Transformational and Deactivation Negation

The present research aimed to examine young and older adults’ comprehension of negated text to determine the locus of older adults’ difficulty in understanding this text construction. Participants were asked to read short passages at their own pace, complete a lexical decision task, and answer a comprehension question about what they had read. Older adults’ comprehension accuracy was lower than that of young adults for passages containing transformational negation. This suggests that limited working memory resources led to older adults’ difficulty with negation, not a difficulty with inhibition, as what would have been suggested with difficulties with deactivation negation.

The influence of word characteristics on the vocabulary of children with cochlear implants.

The goal of this study was to explore the effects of phonotactic probability, word length, word frequency, and neighborhood density on the words known by children with cochlear implants (CIs) varying in vocabulary outcomes in a retrospective analysis of a subset of data from a longitudinal study of hearing loss. Generalized linear mixed modeling was used to examine the effects of these word characteristics at 3 time points: preimplant, postimplant, and longitudinal follow-up. Results showed a robust effect of neighborhood density across group and time, whereas the effect of frequency varied by time. Significant effects of phonotactic probability or word length were not detected. Taken together, these findings suggest that children with CIs may be able to use spoken language structure in a manner similar to their normal hearing counterparts, despite the differences in the quality of the input. The differences in the effects of phonotactic probability and word length imply a difficulty in initiating word learning and limited working memory ability in children with CIs.

The role of memory in processing relative clauses in children with specific language impairment.

This study investigated the relationship between 2 components of memory--phonological short-term memory (pSTM) and working memory (WM)--and the control of relative clause constructions in children with specific language impairment (SLI). Children with SLI and 2 control groups--an age-matched and a younger group of children with typical development--repeated sentences, including relative clauses, representing 5 syntactic roles and 2 levels of matrix clause complexity. The Working Memory Test Battery for Children was administered. All 3 groups showed significant associations between pSTM and both types of matrix clause construction. For children with SLI, significant associations emerged between (a) WM and more complex matrix clause constructions, (b) WM and relative clauses including a range of syntactic roles, and (c) pSTM and the least difficult syntactic role. In contrast, the age-matched control group could repeat almost all syntactic roles without invoking the use of either memory component. The role of pSTM and WM in the production of relative clauses by children with SLI is influenced by the degree of difficulty of the structure to be recalled. In therapy, the effect of WM limitations can be minimized by approaching each structure within the context of a simple matrix clause.

EyeFrame: real-time memory aid improves human multitasking via domain-general eye tracking procedures

OBJECTIVE: We developed an extensively general closed-loop system to improve human interaction in various multitasking scenarios, with semi-autonomous agents, processes, and robots. BACKGROUND: Much technology is converging toward semi-independent processes with intermittent human supervision distributed over multiple computerized agents. Human operators multitask notoriously poorly, in part due to cognitive load and limited working memory. To multitask optimally, users must remember task order, e.g., the most neglected task, since longer times not monitoring an element indicates greater probability of need for user input. The secondary task of monitoring attention history over multiple spatial tasks requires similar cognitive resources as primary tasks themselves. Humans can not reliably make more than ~2 decisions/s. METHODS: Participants managed a range of 4-10 semi-autonomous agents performing rescue tasks. To optimize monitoring and controlling multiple agents, we created an automated short term memory aid, providing visual cues from users' gaze history. Cues indicated when and where to look next, and were derived from an inverse of eye fixation recency. RESULTS: Contingent eye tracking algorithms drastically improved operator performance, increasing multitasking capacity. The gaze aid reduced biases, and reduced cognitive load, measured by smaller pupil dilation. CONCLUSIONS: Our eye aid likely helped by delegating short-term memory to the computer, and by reducing decision making load. Past studies used eye position for gaze-aware control and interactive updating of displays in application-specific scenarios, but ours is the first to successfully implement domain-general algorithms. Procedures should generalize well to: process control, factory operations, robot control, surveillance, aviation, air traffic control, driving, military, mobile search and rescue, and many tasks where probability of utility is predicted by duration since last attention to a task.

Lexical decay during online sentence processing in adults with specific language impairment.

Decay of memory traces is an important component of many theories of working memory, but there is conflicting evidence on whether the rate of decay differs for individuals with specific language impairment (SLI) as compared to peers with typical language. The authors tested the hypothesis that adults with SLI have a slower decay rate. Twenty adults with SLI, ages 18-27 years, and 23 age-matched peers identified target words in sentences. Sentences were presented at normal and slow rates. Participants separately judged whether a picture and sentence matched in meaning as a measure of sentence processing efficiency. After controlling for sentence processing efficiency, the group with SLI was slower to detect words in sentences. Response times for the group with SLI increased less in the slow condition as compared to the group with typical language, resulting in a Group × Presentation Rate interaction. The Group × Presentation Rate interaction is consistent with a slower lexical decay rate for adults with SLI, but differences in the ability to manage interference could not be ruled out. The findings suggest that decay rate differences may play a role in the working memory limitations found in individuals with SLI.

When in doubt follow your nose-a wayfinding strategy.

Route selection is governed by various strategies which often allow minimizing the required memory capacity. Previous research showed that navigators primarily remember information at route decision points and at route turns, rather than at intersections which required straight walking. However, when actually navigating the route or indicating directional decisions, navigators make fewer errors when they are required to walk straight. This tradeoff between location memory and route decisions accuracy was interpreted as a “when in doubt follow your nose” strategy which allows navigators to only memorize turns and walk straight by default, thus considerably reducing the number of intersections to memorize. These findings were based on newly learned routes. In the present study, we show that such an asymmetry in route memory also prevails for planning routes within highly familiar environments. Participants planned route sequences between locations in their city of residency by pressing arrow keys on a keyboard. They tended to ignore straight walking intersections, but they ignored turns much less so. However, for reported intersections participants were quicker at indicating straight walking than turning. Together with results described in the literature, these findings suggest that a “when in doubt follow your nose strategy” is applied also within highly familiar spaces and might originate from limited working memory capacity during planning a route.

Is it random or impulsive responding? The effect of working memory load on decision-making

Research has suggested individuals with limited working memory (WM) capacity make more impulsive choices than individuals without such limited capacity; however, the specificity of increased impulsivity has been challenged on the grounds that limited WM may lead to an increase in random responding rather than a true increase in impulsivity. Furthermore, whereas some previous research have demonstrated sex differences in decision-making, with males tending to make a higher proportion of impulsive decisions than females, the overall results in this area have been mixed. Thus, the current study specifically controlled for the impact of sex, a potential key issue within this area. In this study, 120 subjects (60 males) were randomly assigned to a WM load or control group and completed a decision-making task requiring rapid decisions. The task utilised three probability of loss conditions. The main findings centred on an interaction between sex and WM load, with males showing increased impulsive decision-making in WM load conditions, whereas females did not show a change in decision-making patterns under WM load. Results of this study support the claim that decreased WM capacity increases impulsive decision-making rather than random responding in men, whereas WM load was unrelated to risk-taking in women.

Assessment of attention and inhibitory control in rodent developmental neurotoxicity studies

In designing screens to assess potential neurotoxicants, the paramount goal is that the selected assessment tools detect dysfunction if it exists. This goal is particularly challenging in the case of cognitive assessments. Cognition is not a unitary phenomenon, and indeed there is growing evidence that different aspects of cognitive functioning are subserved by distinct neural systems. As a result, if a particular neurotoxicant selectively damages certain neural systems but not others, it can impair some cognitive, sensory, or affective functions, but leave many others intact. Accordingly, studies with human subjects use batteries of cognitive tests, cognizant of the fact that no one test is capable of detecting all forms of cognitive dysfunction. In contrast, assessment of cognitive functioning in non-human animal developmental neurotoxicity (DNT) studies typically consists of a single, presumably representative, “learning and memory” task that is expected to detect all potential effects on cognitive functioning. Streamlining the cognitive assessment in these studies saves time and money, but these shortcuts can have serious consequences if the aspect of cognitive functioning that is impaired is not tapped by the single selected task. In particular, executive functioning – a constellation of cognitive functions which enables the organism to focus on multiple streams of information simultaneously, and revise plans as necessary – is poorly assessed in most animal DNT studies. The failure to adequately assess these functions – which include attention, working memory, inhibitory control, and planning – is particularly worrisome in light of evidence that the neural systems that subserve these functions may be uniquely vulnerable to early developmental insults. We illustrate the importance of tapping these areas of functioning in DNT studies by describing the pattern of effects produced by early developmental Pb exposure. Rats exposed to lead (Pb) early in development were tested on a series of automated attention tasks, as well as on a radial arm maze task. The lead-exposed rats were not impaired in this demanding radial arm maze task, despite conditions which tapped the limits of both working and long-term memory. In contrast, the automated tests designed to assess rodent executive functioning revealed selective and functionally important deficits in attention and regulation of emotion or negative affect (produced by committing an error or not receiving an expected reward). This example underscores the importance of including tasks to specifically tap executive functioning in DNT batteries. Such tasks are not only sensitive but can also shed light on the specific nature of the dysfunction, and they can implicate dysfunction of specific neural systems, information which can be used to design therapeutic interventions. Although the use of such tasks increases the time and effort needed to complete the battery, the benefits outweigh the cost, in light of the greater sensitivity of the battery and the more complete characterization of effects.

Developmental origins of recoding and decoding in memory

Working memory is severely limited in both adults and children, but one way that adults can overcome this limit is through the process of recoding. Recoding happens when representations of individual items are chunked together into a higher order representation, and the chunk is assigned a label. That label can then be decoded to retrieve the individual items from long-term memory. Whereas this ability has been extensively studied in adults (as, for example, in classic studies of memory in chess), little is known about recoding’s developmental origins. Here we asked whether 2- to 3-year-old children also can recode—that is, can they restructure representations of individual objects into a higher order chunk, assign this new representation a verbal label, and then later decode the label to retrieve the represented individuals from memory. In Experiments 1 and 2, we showed children identical blocks that could be connected to make tools. Children learned a novel name for a tool that could be built from two blocks, and for a tool that could be built from three blocks. Later we told children that one of the tools was hidden in a box, with no visual information provided. Children were allowed to search the box and retrieve varying numbers of blocks. Critically, the retrieved blocks were identical and unconnected, so the only way children could know whether any blocks remained was by using the verbal label to recall how many objects comprised each tool (or chunk). We found that even children who could not yet count adjusted their searching of the box depending on the label they had heard. This suggests that they had recoded representations of individual blocks into higher-order chunks, attached labels to the chunks, and then later decoded the labels to infer how many blocks were hidden. In Experiments 3 and 4 we asked whether recoding also can expand the number of individual objects children could remember, as in the classic studies with adults. We found that when no information was provided to support recoding, children showed the standard failure to remember more than three hidden objects at once. But when provided recoding information, children successfully represented up to five individual objects in the box, thereby overcoming typical working memory limits. These results are the first demonstration of recoding by young children; we close by discussing their implications for understanding the structure of memory throughout the lifespan.

Neural Anatomy of Primary Visual Cortex Limits Visual Working Memory.

Despite the immense processing power of the human brain, working memory storage is severely limited, and the neuroanatomical basis of these limitations has remained elusive. Here, we show that the stable storage limits of visual working memory for over 9 s are bound by the precise gray matter volume of primary visual cortex (V1), defined by fMRI retinotopic mapping. Individuals with a bigger V1 tended to have greater visual working memory storage. This relationship was present independently for both surface size and thickness of V1 but absent in V2, V3 and for non-visual working memory measures. Additional whole-brain analyses confirmed the specificity of the relationship to V1. Our findings indicate that the size of primary visual cortex plays a critical role in limiting what we can hold in mind, acting like a gatekeeper in constraining the richness of working mental function.

Sentence repetition is a measure of children's language skills rather than working memory limitations.

Sentence repetition tasks are widely used in the diagnosis and assessment of children with language difficulties. This paper seeks to clarify the nature of sentence repetition tasks and their relationship to other language skills. We present the results from a 2-year longitudinal study of 216 children. Children were assessed on measures of sentence repetition, vocabulary knowledge and grammatical skills three times at approximately yearly intervals starting at age 4. Sentence repetition was not a unique longitudinal predictor of the growth of language skills. A unidimensional language latent factor (defined by sentence repetition, vocabulary knowledge and grammatical skills) provided an excellent fit to the data, and language abilities showed a high degree of longitudinal stability. Sentence repetition is best seen as a reflection of an underlying language ability factor rather than as a measure of a separate construct with a specific role in language processing. Sentence repetition appears to be a valuable tool for language assessment because it draws upon a wide range of language processing skills.

Reference-Set Computation in Children: Mandarin-Speaking Children’s Pronoun Interpretation in Avoid Pronoun Contexts

Reinhart’s (2004, 2006) theory predicts that children should perform around chance on tasks involving reference-set computation due to their working memory limitations. The purpose of this article is to test her theory against acquisition data from a previously unexplored area of reference-set computation. We present an experiment designed to examine Mandarin-speaking children’s pronoun interpretation in contexts where the Avoid Pronoun Principle is operative. Since the computation of the Avoid Pronoun Principle requires reference-set computation, children are expected to show difficulty resolving pronouns in such contexts. This prediction was confirmed in our experiment, where otherwise linguistically competent 5-year-olds performed around chance when confronted with the need to compute the Avoid Pronoun Principle. Moreover, analysis of individual data suggests that their nonadultlike performance is due not to their lack of the relevant knowledge but to their lack of capacity to process the required computation.

On second language processing and grammatical development

The parsing-to-learn hypothesis (Fodor, 1998) identifying the parser as the language acquisition device (PLAD) is discussed for second-language (L2) grammatical acquisition. Parsing is assumed to involve concomitant UG-sanctioned structure generation and licensing by a parameterized lexicon. In this architecture, licensing induces immediate changes to the lexical knowledge base as new feature matrices for categories and their exponents are registered. Stages arise as these matrices are increasingly activated and can be accessed within the narrow window imposed by working-memory limitations. Specifically, the PLAD instantiates feature re-assembly (Lardiere, 2009) in response to licensing failures (Clark & Roberts, 1993), characterizing transitions between grammatical states (Gregg, 1996, 2003) in the Full Transfer/Full Access model (Schwartz & Sprouse, 1994, 1996). The PLAD is examined in light of current research and of evidence showing mandatory engagement of syntax, breakdown reflecting feature organization, and domain-specificity. The PLAD offers potentially fruitful insights about L2 parsing and grammatical development.