Response Time Variability Research Articles

Proactive control processes in event-based prospective memory: Evidence from intraindividual variability and ex-Gaussian analyses.

The present study implemented an individual differences approach in conjunction with response time (RT) variability and distribution modeling techniques to better characterize the cognitive control dynamics underlying ongoing task cost (i.e., slowing) and cue detection in event-based prospective memory (PM). Three experiments assessed the relation between proactive control ability, ex-Gaussian parameter estimates (μ and τ), intraindividual variability in responding (coefficient of variation, CoV), and PM cue detection. Experiment 1 examined these relations using a standard nonfocal PM paradigm. Experiments 2 and 3 further assessed how PM importance and PM cue focality, respectively, influenced performance. Across all experiments, nonfocal PM was associated with increases in all cost measures, but only μ reliably predicted cue detection. Importance instructions and focal PM cues selectively increased and decreased μ cost, respectively, relative to the standard nonfocal condition. These findings suggest that μ cost may reflect a target-checking process that benefits cue detection and produces slowing throughout the entire ongoing task. Additionally, across all experiments proactive control was positively associated with μ cost and cue detection, and generally negatively associated with variability cost (τ and CoV). These findings suggest that natural variation in proactive control ability may affect reliance on more efficacious monitoring processes that facilitates cue detection. Furthermore, variability in responding may have little influence on successful PM. The results from the current study highlight the utility of RT variability and distribution analyses in understanding PM costs and have important implications for extant theories of PM concerning the cognitive control processes underlying cue detection. (PsycINFO Database Record

Working Memory and Intraindividual Variability in Response Time Mediate Fluid Intelligence Deficits Associated With ADHD Symptomology

Objective: To determine if decreased fluid intelligence was associated with ADHD, and was mediated by deficits in working memory and intraindividual variability in motor responding. Method: The present study tested 142 young adults from the general population on a range of working memory, response time, and fluid intelligence tasks, and an ADHD self-report symptoms questionnaire. Results: Total and hyperactive ADHD symptoms correlated significantly and negatively with fluid intelligence, but this association was fully mediated by both working memory and intraindividual variability in response time. However, inattentive symptoms were not associated with fluid intelligence. Conclusion: These results have important implications for clinicians using speeded psychometric tests as part of their assessment battery, working memory interventions for ADHD patients that focus on performance improvement without controlling for response consistency, and also demonstrate potential differences in the neuropsychological profiles of ADHD subtypes.

CTS: An operating system CPU scheduler to mitigate tail latency for latency-sensitive multi-threaded applications

Large-scale interactive Web services break a user’s request to many sub-requests and send them to a large number of independent servers so as to consult multi-terabyte datasets instantaneously. Service responsiveness hinges on the slowest server, making the tail of the latency distribution of individual servers a matter of great concern. A large number of latency-sensitive applications hosted on individual servers use thread-driven concurrency model wherein a thread is spawned for each user connection. Threaded applications rely on the operating system CPU scheduler for determining the order of thread execution. Our experiments show that the default Linux scheduler (CFS) idiosyncrasies result in LCFS (Last Come First Served) scheduling of threads belonging to the same application. On the other hand, studies have shown that FCFS (First Come First Served) scheduling yields the lowest response time variability and tail latency, making the default scheduler of Linux a source of long tail latency for multi-threaded applications. In this paper, we present CTS, an operating system CPU scheduler to trim the tail of the latency distribution for latency-sensitive multi-threaded applications while maintaining the key characteristics of the default Linux scheduler (e.g., fairness). By adding new data structures to the Linux kernel, CTS tracks threads belonging to an application in a timely manner and schedules them in FCFS manner, mitigating the tail latency. To keep the existing features of the default Linux scheduler intact, CTS keeps CFS responsible for system-wide load balancing and core level process scheduling; CTS merely schedules threads of the CFS chosen process in FCFS order, ensuring tail latency mitigation without sacrificing the default Linux scheduler properties. Experiments with a prototype implementation of CTS in the Linux kernel demonstrate that CTS significantly outperforms the Linux default scheduler. For example, CTS mitigates the tail latency of a Null RPC server by up to 96%, a Thrift server by up to 90% and an Apache Web server by up to 51% at 99.9th percentile.

Intra-individual variability across cognitive task in drug-naïve pediatric patients with obsessive compulsive disorder

Attention deficit is commonly observed in several psychiatric conditions. In particular, patients with attention deficit hyperactivity disorder exhibit not only attention deficit, but also intra-individual variability in response times (IIV-RT) during the performance of cognitive tasks related to attention span and sustained attention. Although obsessive compulsive disorder (OCD) is commonly observed across childhood, little is known about abnormalities in IIV-RT during the auditory odd-ball task, and how these changes relate to event-related potentials (ERPs) components. In the present study, we compared the ERPs of 15 adolescent and pediatric patients with OCD with 15 healthy age, sex, and IQ-matched controls. We found that tau of IIV-TR was not significantly different between the OCD group and controls, whereas the OCD group exhibited lower mu and sigma compared to controls. Furthermore, we revealed that P300 amplitude was significantly attenuated in the OCD group at Fz, C3, and C4, compared with controls. The present study thereby provided the first evidence that individuals with pediatric or adolescent OCD exhibit lower variability in reaction time in IIV-RT during an auditory odd-ball task than controls. These results suggest that there are no impairments in attention span and sustained attention in pediatric and adolescent patients with OCD.

T67. Is Increased Response Time Variability Related to Deficient Emotional Self-Regulation in Children With ADHD?

T67. Is Increased Response Time Variability Related to Deficient Emotional Self-Regulation in Children With ADHD?

The relative importance of perceptual and memory sampling processes in determining the time course of absolute identification.

In absolute identification, the extended generalized context model (EGCM; Kent & Lamberts, 2005, 2016) proposes that perceptual processing determines systematic response time (RT) variability; all other models of RT emphasize response selection processes. In the EGCM-RT the bow effect in RTs (longer responses for stimuli in the middle of the range) occurs because these middle stimuli are less isolated, and as perceptual information is accumulated, the evidence supporting a correct response grows more slowly than for stimuli at the ends of the range. More perceptual information is therefore accumulated in order to increase certainty in response for middle stimuli, lengthening RT. According to the model reducing perceptual sampling time should reduce the size of the bow effect in RT. We tested this hypothesis in 2 pitch identification experiments. Experiment 1 found no effect of stimulus duration on the size of the RT bow. Experiment 2 used multiple short stimulus durations as well as manipulating set size and stimulus spacing. Contrary to EGCM-RT predictions, the bow effect on RTs was large for even very short durations. A new version of the EGCM-RT could only capture this, alongside the effect of stimulus duration on accuracy, by including both a perceptual and a memory sampling process. A modified version of the selective attention, mapping, and ballistic accumulator model (Brown, Marley, Donkin, & Heathcote, 2008) could also capture the data, by assuming psychophysical noise diminishes with increased exposure duration. This modeling suggests systematic variability in RT in absolute identification is largely determined by memory sampling and response selection processes. (PsycINFO Database Record

Sleep deprivation increases the costs of attentional effort: Performance, preference and pupil size

Sleep deprivation (SD) consistently degrades performance in tasks requiring sustained attention, resulting in slower and more variable response times that worsen with time-on-task. Loss of motivation to exert effort may exacerbate performance degradation during SD. To test this, we evaluated sustained performance on a vigilance task, combining this with an effort-based decision-making task and pupillometry. Vigilance was tested at rest and after sleep deprivation, under different incentive conditions (1, 5 or 15 cents for fast responses). Subsequently, preference measures were collected from an effort-discounting task, in which a commensurate reward was offered for maintaining attentional performance for different durations (1, 5, 10, 20 or 30 min). Vigilance was impaired during SD, in a manner modulated by reward value. Preference metrics showed that the value of available rewards was discounted by task duration, an effect compounded by SD. Pupillometry revealed that arousal was modulated during SD in a value-based manner, and moment-to-moment fluctuations in pupil diameter were directly predictive of performance. Together, these data demonstrate that attentional performance can be interpreted within a value-based effort allocation framework, such that the perceived cost of attentional effort increases after sleep deprivation.

Identification of service improvement opportunities in an Australian community transition care program

Transition care programs (TCPs) are designed to optimise functional recovery and independence in older adults post-hospitalisation. These programs are under high demand, and understanding inefficiencies in patient flow are a key step towards service improvement. To identify service improvement opportunities in an Australian community TCP service. An in-depth retrospective study of 113 community TCP clients. TCP occupancy was high (94%) and client functional level improved across the program. Inefficiencies experienced included: admission delays to the program; low completion rates (61%) predominantly due to re-hospitalisation; variable response times by Allied Health services (5-20days); and discharge delays-the latter attributed to waiting for services such as Home Care Packages through Non-Government Organisations. This study identified several opportunities for service improvement in a community TCP service. Health practitioners should be regularly provided with up-to-date information on efficiency of TCP services.

Children’s Allocation of Study Time during the Solution of Raven’s Progressive Matrices

The acuity of reasoning on Raven’s Progressive Matrices is strongly influenced by strategic determinants. Building on metamemory studies that highlight the influence of study-time allocation on memory development, we investigated children’s allocation of study time while solving these matrices. A total of 170 children aged 6–12 years completed a computerized short-form version of the standard matrices featuring items selected to represent a broad range of difficulties. Beyond analyzing changes in mean latencies and performances with age, we used generalized additive mixed models to explore within-participant variability in response times as a function of both item complexity and overall individual efficiency. Results revealed that individual differences in performances were significantly associated with children’s adaptive modulation of response times. Mediation analysis further indicated that response-time modulation contributed to age-related changes in performance. Taking account of study-time allocation in reasoning tasks may open up new avenues for the study of reasoning development and the assessment of intellectual functioning.

Detecting malingering in traumatic brain injury: Combining response time with performance validity test accuracy

Objective: The present study examined the incremental utility of item-level response time (RT) variables on a traditional performance validity test in distinguishing adults with verified TBI from adults coached to feign neurocognitive impairment.Method: Participants were 45 adults with moderate to severe TBI, 45 healthy adults coached to feign neurocognitive impairment (SIM), and 61 healthy adult comparisons providing full effort (HC). All participants completed a computerized version of the Test of Memory Malingering (TOMM-C) in the context of a larger test battery. RT variables examined along with TOMM-C accuracy scores included mean RTs (Trial 1, Trial 2, correct and incorrect trials) and RT variability indices.Results: Several RT indices differed significantly across the groups. In general, SIM produced longer, more variable RTs than HC and TBI. Of the RT indices, average RT for Trial 1 and 2 were the best predictors of group membership; however, classification accuracies were greatly influenced by the groups being compared. Average RT for Trial 1 and 2 showed excellent discrimination of SIM and HC. All RT indices were less successful in discriminating SIM and TBI. Average RT for Trial 1 and 2 added incremental predictive value to TOMM-C accuracy in distinguishing SIM from TBI.Conclusion: Findings contribute to a limited body of research examining the incremental utility of combining RT with traditional PVTs in distinguishing feigned and bona fide TBI. Findings support the hypothesis that combining RT with TOMM-C accuracy can improve its diagnostic accuracy. Future research with other groups of clinical interest is recommended.

The Effects of 10 Hz Transcranial Alternating Current Stimulation on Audiovisual Task Switching.

Neural oscillations in the alpha band (7–13 Hz) are commonly associated with disengagement of visual attention. However, recent studies have also associated alpha with processes of attentional control and stability. We addressed this issue in previous experiments by delivering transcranial alternating current stimulation at 10 Hz over posterior cortex during visual tasks (alpha tACS). As this stimulation can induce reliable increases in EEG alpha power, and given that performance on each of our visual tasks was negatively associated with alpha power, we assumed that alpha tACS would reliably impair visual performance. However, alpha tACS was instead found to prevent both deteriorations and improvements in visual performance that otherwise occurred during sham & 50 Hz tACS. Alpha tACS therefore appeared to exert a stabilizing effect on visual attention. This hypothesis was tested in the current, pre-registered experiment by delivering alpha tACS during a task that required rapid switching of attention between motion, color, and auditory subtasks. We assumed that, if alpha tACS stabilizes visual attention, this stimulation should make it harder for people to switch between visual tasks, but should have little influence on transitions between auditory and visual subtasks. However, in contrast to this prediction, we observed no evidence of impairments in visuovisual vs. audiovisual switching during alpha vs. control tACS. Instead, we observed a trend-level reduction in visuoauditory switching accuracy during alpha tACS. Post-hoc analyses showed no effects of alpha tACS in response time variability, diffusion model parameters, or on performance of repeat trials. EEG analyses also showed no effects of alpha tACS on endogenous or stimulus-evoked alpha power. We discuss possible explanations for these results, as well as their broader implications for current efforts to study the roles of neural oscillations in cognition using tACS.

Attentional fluctuations in preschoolers: Direct and indirect relations with task accuracy, academic readiness, and school performance

Attentional control fluctuates in the presence of internal and external distractors, wandering on and off a given task. The current study investigated individual differences in attentional fluctuations in 250 preschoolers. Attentional fluctuations were assessed via intra-individual variability in response time in a Go/No-Go task. Greater fluctuations in attentional control were linked to lower task accuracy. In addition, greater attentional fluctuations predicted lower performance in a task of cognitive flexibility, the Dimensional Change Card Sort task. Attentional fluctuations were also associated with laboratory measures of academic readiness in preschool, as assessed by the Applied Problems and Letter–Word Identification subscales of the Woodcock–Johnson III Tests of Achievement, which in turn predicted teacher reports of academic performance in first grade. Attentional fluctuations also had indirect associations with emergent math skills in preschool, via cognitive flexibility, as well as indirect associations with first-grade teacher reports of academic performance, via the relations between cognitive flexibility and emergent math skills in preschool. These results suggest that consistency is an important aspect of attentional control during early childhood.

Possible Age-Related Progression of Attentional Impairment in ADHD and Its Attenuation by Past Diagnosis and Treatment

Objective: The aim of the study is to evaluate attentional impairment in different age groups with ADHD. Method: In all, 58 children, 73 adolescents, and 104 adults with ADHD were evaluated using the Test of Variables of Attention (TOVA). Subjects with comorbidities or psychotropic treatment were not included. Results: Considering Response Time Variability (RTV), adults were 10.6 and 4.0 times more likely to be severely impaired (standard score < 40) than children and adolescents, respectively. Adults were twice as likely as adolescents to be very impaired (standard score< 70) in Omissions. Considering d′ (decrement of attentional performance over time), all severely impaired participants were adults. Age predicted impairment in Attention Performance Index (API), RTV, and d′, but not Omissions or Commissions. Past treatment with stimulants predicted less impairment in d′, past diagnosis predicted less impairment in RTV, and each predicted less impairment in Omissions and API. Conclusion: Adults had more attentional impairment than children and adolescents. Past diagnosis and treatment were associated with less ADHD-related attentional impairment.

Sleep deprivation increases the costs of attentional effort: performance, preference and pupil size

Abstract Sleep deprivation (SD) consistently degrades performance in tasks requiring sustained attention, resulting in slower and more variable response times that worsen with time-on-task. Loss of motivation to exert effort may exacerbate performance degradation during SD. To test this, we evaluated sustained performance on a vigilance task, combining this with an effort-based decision-making task and pupillometry. Vigilance was tested at rest and after sleep deprivation, under different incentive conditions (1, 5 or 15 cents for fast responses). Subsequently, preference measures were collected from an effort-discounting task, in which a commensurate reward was offered for maintaining attentional performance for different durations (1, 5, 10, 20 or 30 min). Vigilance was impaired during SD, in a manner modulated by reward value. Preference metrics showed that the value of available rewards was discounted by task duration, an effect compounded by SD. Pupillometry revealed that arousal was modulated during SD in a value-based manner, and moment-to-moment fluctuations in pupil diameter were directly predictive of performance. Together, these data demonstrate that attentional performance can be interpreted within a value-based effort allocation framework, such that the perceived cost of attentional effort increases after sleep deprivation.

Cutting Latency Tail: Analyzing and Validating Replication without Canceling

Response time variability in software applications can severely degrade the quality of the user experience. To reduce this variability, request replication emerges as an effective solution by spawning multiple copies of each request and using the result of the first one to complete. Most previous studies have mainly focused on the mean latency for systems implementing replica cancellation, i.e., all replicas of a request are canceled once the first one finishes. Instead, we develop models to obtain the response-time distribution for systems where replica cancellation may be too expensive or infeasible to implement, as in “fast” systems, such as web services, or in legacy systems. Furthermore, we introduce a novel service model to explicitly consider correlation in the processing times of the request replicas, and design an efficient algorithm to parameterize the model from real data. Extensive evaluations on a MATLAB benchmark and a three-tier web application (MediaWiki) show remarkable accuracy, e.g., 7 (4 percent) average error on the 99th percentile response time for the benchmark (respectively, MediaWiki), the requests of which execute in the order of seconds (respectively, milliseconds). Insights into optimal replication levels are thereby gained from this precise quantitative analysis, under a wide variety of system scenarios.

Attention profiles in childhood absence epilepsy compared with attention-deficit/hyperactivity disorder

ObjectiveThis study aimed to compare the attention profiles of subjects with childhood absence epilepsy (CAE) to those of children with attention-deficit/hyperactivity disorder (ADHD) and controls. MethodWe retrospectively reviewed the medical records of 20 children (age 7.2 ± 1.6 years, 5 boys) in whom CAE was diagnosed at the Department of Pediatric Neurology of Asan Medical Center, Seoul, Korea. ADHD and control subjects were selected from children who visited the Department of Pediatric Psychiatry and were confirmed as having or not having ADHD based on Diagnostic and Statistical Manual of Mental Disorders (DSM-IV) and the Schedule for Affective Disorders and Schizophrenia for School-Age Children-Present and Lifetime version (K-SADS-PL). The 20 children with CAE, 20 with ADHD and 20 controls completed the Advanced Test of Attention (ATA), which is a computerized continuous performance task. ResultsThe CAE subjects without ADHD showed increased Omission errors (p=.013) on the visual ATA and Response time (p=0.044) on the auditory ATA than the controls, although these differences did not remain significant after multiple comparison correction. The CAE subjects without ADHD had significantly decreased Response time variability on the visual ATA than the ADHD group (p<0.001). The CAE subjects with comorbid ADHD showed increased Commission errors (p=0.020) and Response time variability (p=0.016) on the visual ATA and increased Commission errors (p=0.022) on the auditory ATA than the CAE subjects without ADHD, although statistical significance disappeared after multiple comparison adjustments. ConclusionThese findings suggest that selective attention is impaired in children with CAE and comorbid ADHD contributes to further impairment of sustained attention and response inhibition.

Development of a Computerized Assessment Tool for Hand-arm Function After Stroke: Test-retest Reliability and Convergent Validity

A new computer game-based hand-arm function evaluation (GHA) tool has been established to quantify fine and gross object manipulation skills, movement quality, accuracy, response time, and movement variation. The tool can be used with numerous objects with various geometric/surface properties, functional and anatomical demands. The purpose of this study was to determine the test-retest reliability and convergent validity (WMFT) of the GHA assessment tool. We hypothesized a high test-retest reliability and a moderate convergent validity.

A Comprehensive Comparison of Quantifications of Intraindividual Variability in Response Times: A Measurement Burst Approach.

To formally identify and contrast the most commonly-employed quantifications of response time inconsistency (RTI) and elucidate their utility for understanding within-person (WP) and between-person (BP) variation in cognitive function with increasing age. Using two measurement burst studies of cognitive aging, we systematically identified and computed five RTI quantifications from select disciplines to examine: (a) correlations among RTI quantifications; (b) the distribution of BP and WP variation in RTI; and (c) the comparability of RTI quantifications for predicting attention switching. Comparable patterns were observed across studies. There was significant variation in RTI BP as well as WP across sessions and bursts. Correlations among RTI quantifications were generally strong and positive both WP and BP, except for the coefficient of variation. Independent prediction models indicated that slower mean response time (RT) and greater RTI were associated with slower attention switching both WP and BP. For selecting simultaneous prediction models, collinearity resulted in inflated standard errors and unstable model estimates. RTI reflects a novel dimension of performance that is a robust and theoretically informative predictor of BP and WP variation in cognitive function. Among the plenitude of RTI quantifications, not all are interchangeable, nor of comparable predictive utility.

Strategic Complexity and the Value of Thinking

Response times are a simple low-cost indicator of the process of reasoning in strategic games. In this paper, we leverage the dynamic nature of response-time data from repeated strategic interactions to measure the strategic complexity of a situation by how long people think on average when they face that situation (where we categorize situations according to the characteristics of play in the previous round). We find that strategic complexity varies significantly across situations, and we find considerable heterogeneity in how responsive subjects' thinking times are to complexity. We also study how variation in response times at the individual level across rounds affects strategic behavior and success. We find that 'overthinking' is detrimental to performance: when a subject thinks for longer than she would normally do in a particular situation, she wins less frequently and earns less. The behavioral mechanism that drives the reduction in performance is a tendency to move away from Nash equilibrium behavior. Overthinking is detrimental even though subjects who think for longer on average tend to be more successful. Finally, cognitive ability and personality have no effect on average response times.

Theta and Alpha Oscillations during the Retention Period of Working Memory by rTMS Stimulating the Parietal Lobe.

Studies on repetitive transcranial magnetic stimulation (rTMS) have shown that stimulating the parietal lobe, which plays a role in memory storage, can enhance performance during the “retention” process of working memory (WM). However, the mechanism of rTMS effect during this phase is still unclear. In this study, we stimulated the superior parietal lobe (SPL) using 5-Hz rTMS in 26 participants and recorded electroencephalography (EEG) while they performed a delayed-recognition WM task. The analyses included the comparisons of event-related spectral perturbation (ERSP) value variations in theta (4–7 Hz) and alpha (8–14 Hz) band frequencies between conditions (rTMS vs. sham), as well as the correlations between different brain areas. Following rTMS, the ERSP values of theta-band oscillations were significantly increased in the parietal and occipital-parietal brain areas (P < 0.05*), whereas the ERSP values of alpha-band oscillations were significantly decreased in the parietal area (P < 0.05*). The ERSP value variations of theta-band oscillations between the two conditions in the left parietal and left prefrontal areas were positively correlated with the response time (RT) variations (by using rTMS, the more subject RT decreased, the more ERSP value of theta oscillation increased). The ERSP value variations of alpha-band oscillations in the left parietal and bilateral prefrontal areas were negatively correlated with RT variations (by using rTMS, the more RT of the subject decreased, the more ERSP value of alpha oscillation decreased). Inter-sites phase synchronization of theta-band EEG between the left parietal and left prefrontal areas, as well as alpha-band EEG between the left parietal and bilateral prefrontal areas were enhanced by rTMS. These results indicated that activities of both parietal and prefrontal areas were required for information storage, and these activities were related to the behavioral responses. Moreover, the connectivity between these two regions was intensified following rTMS. Thus, rTMS may affect the frontal area indirectly via the frontal parietal pathway.