Blocks Of Task Research Articles

P178 Does current strength interact with baseline performance to influence tDCS outcome? A replication study

Introduction TDCS studies have recently faced strong criticism for exhibiting both a large intra- and inter-subject response variability and a low reproducibility of effects. We here attempt to replicate one of our own recent studies. In this study, we found a rightward shift of spatial attention bias, relative to a leftward (“pseudoneglect”) bias at baseline (as indexed by the landmark task ) using a bi-hemispheric montage (P5-aTCS/P6-cTDCS, Dual tDCS) to affect the balance of activity between the left versus right posterior parietal cortices (PPCs). This effect was overall weak (near significant trend in 40 participants), but displayed a complex, non-linear interaction between current strength and baseline task performance, indicating inter-individual variability in sensitivity to tDCS according to baseline state and intensity. Objectives Using a within-subjects design (vs between-subjects in our previous study) to further test and replicate baseline state- and intensity-dependency of tDCS outcome. Methods 20 adults received 1 mA & 2 mA Dual, and Sham tDCS, counterbalanced across different days. In each session, 6 blocks of the landmark task were completed (2 pre-tDCS, 2 during-tDCS and 2 post-tDCS). Dual tDCS was applied for 15 min (Sham = 30 s). Subjects were divided into good/poor baseline performance groups. Results We found no overall effects of tDCS on landmark task performance, nor any interaction with the factors baseline state or tDCS intensity. Our data are however not fully conclusive as there are group-level spatial bias differences at baseline between the 3 testing sessions that may confound the results (and were not present in our previous study). Further recordings are needed to resolve this point (that we hope to present at the conference). Conclusion We believe more replication studies (within- or across participants) are needed to establish reproducibility of tDCS effects.

P160 Enhanced biasing effect of prior knowledge on perceptual decision processes following continuous theta burst stimulation of motor cortex

Introduction Separate interneuron circuits in human motor cortex (M1) have been suggested to subserve different forms of motor behaviour, but it is not clear what role they play in other aspects such as decision-to-action processes. Objectives We tested whether two distinct interneuron networks in M1 play different roles in perceptual decision-making. Materials & methods 10 participants completed 3 blocks of a decision making task in each of 2 measurement sessions. Participants responded to a left/right visual imperative cue with left/right hand key presses. A random dot kinetogram (RDK) with 2 levels of coherent motion (low, high) preceded the visual cue. In 80% of trials the motion direction of the dots was congruent with that of the imperative cue, and thus could be used to prepare a response in advance. Accuracy and reaction time (RT) associated with correct responses in congruent trials were measured. A controllable pulse parameter transcranial magnetic stimulation (cTMS; Rogue Resolutions Ltd.) device was used to target distinct interneuron circuits in M1 by changing the coil orientation (posterior-anterior, PA; anterior-posterior, AP) and pulse width (45–75 μ s). A continuous theta burst stimulation (cTBS) protocol was applied with AP45 or PA75 pulses, in separate sessions, to the left M1 following the first block of the decision-making task. Results Accuracy of responses was typically ⩾95%, therefore we focus on RTs. As expected, RTs were faster with high versus low RDK coherence (Fig. 1A–D). There was no effect of pulse type on RTs, but ANOVA revealed an interaction of hand, block and coherence (P = 0.029). Calculating the percentage change in RT from low to high coherence trials (Fig. 1E and F) revealed an improvement in RTs for right, but not left, hand responses in high, but not low, coherence trials immediately after cTBS. Conclusion Irrespective of the pulse type, and thus M1 interneuron circuits targeted, cTBS over left M1 enhanced the bias effect for corresponding right hand responses, but only following high coherence RDK. cTBS may have altered the integration in M1 of the sensory evidence from the bias and imperative cue, giving more weight to the bias which normally has a relatively minor influence. Download : Download high-res image (772KB) Download : Download full-size image

Effect of Experimental Hand Pain on Training-Induced Changes in Motor Performance and Corticospinal Excitability.

Pain influences plasticity within the sensorimotor system and the aim of this study was to assess the effect of pain on changes in motor performance and corticospinal excitability during training for a novel motor task. A total of 30 subjects were allocated to one of two groups (Pain, NoPain) and performed ten training blocks of a visually-guided isometric pinch task. Each block consisted of 15 force sequences, and subjects modulated the force applied to a transducer in order to reach one of five target forces. Pain was induced by applying capsaicin cream to the thumb. Motor performance was assessed by a skill index that measured shifts in the speed–accuracy trade-off function. Neurophysiological measures were taken from the first dorsal interosseous using transcranial magnetic stimulation. Overall, the Pain group performed better throughout the training (p = 0.03), but both groups showed similar improvements across training blocks (p < 0.001), and there was no significant interaction. Corticospinal excitability in the NoPain group increased halfway through the training, but this was not observed in the Pain group (Time × Group interaction; p = 0.01). These results suggest that, even when pain does not negatively impact on the acquisition of a novel motor task, it can affect training-related changes in corticospinal excitability.

Executive Functioning of Sexually Compulsive and Non-Sexually Compulsive Men Before and After Watching an Erotic Video

IntroductionDespite the serious behavioral consequences faced by individuals with sexual compulsivity, related neuropsychological studies are sparse. AimTo compare decision making and cognitive flexibility at baseline and after exposure to an erotic video in sexually compulsive participants and non-sexually compulsive controls. MethodsThe sample consisted of 30 sexually compulsive men and 30 controls. Cognitive flexibility was investigated through the Wisconsin Card Sorting Test and decision making was examined through the Iowa Gambling Task. Main Outcome MeasuresWisconsin Card Sorting Test categories, correct responses, and perseverative errors and Iowa Gambling Task general trends and blocks. ResultsSexually compulsive subjects and controls performed similarly at baseline. After watching an erotic video, controls performed better in block 1 of the Iowa Gambling Task (P = .01) and had more correct responses on the Wisconsin Card Sorting Test (P = .01). ConclusionsThe controls presented fewer impulsive initial choices and better cognitive flexibility after exposure to erotic stimuli.Messina B, Fuentes D, Tavares H, et al. Executive Functioning of Sexually Compulsive and Non-Sexually Compulsive Men Before and After Watching an Erotic Video. J Sex Med 2017;14:347–354.

Relationships Between Gum Chewing and Stroop Test: A Pilot Study.

Cognitive function tends to decrease with aging, therefore maintenance of this function in an aging society is an important issue. The role of chewing in nutrition is important. Although several studies indicate that gum chewing is thought to improve cognitive function, it remains debatable whether gum-chewing does in fact improve cognitive function. The Stroop test is a psychological tool used to measure cognition. A shorter reaction time indicates a mean higher behavioral performance and higher levels of oxy-Hb concentration. fNIRS is a powerful, non-invasive imaging technique offering many advantages, including compact size, no need for specially equipped facilities, and the potential for real-time measurement. The left dorsolateral prefrontal cortex (DLPFC) seems to be mainly involved in the Stroop task.The aim of the present study was to investigate the hypothesis that gum-chewing changes cerebral blood flow in the left DLPFC during the Stroop test, and also changes the reaction time. Fourteen healthy volunteers (mean age 26.9years) participated in this study after providing written informed consent. A piece of tasteless gum weighing 1.0g was used. Each session was designed in a block manner, i.e. 4 rests (30s) and 3 blocks of task (30s). A computerized Stroop test was used (including both congruent and incongruent Stroop tasks) which calculates a response time automatically. The Binominal test was used for comparisons (p<0.05). The results show activation of the left DLPFC during the Stroop task and that gum chewing significantly increases responses/oxy-Hb concentration and significantly shortens the reaction time.

Intraocular pressure is sensitive to cumulative and instantaneous mental workload

We used a repeated-measures design to assess the impact of mental-task complexity on intraocular pressure (IOP). Fourteen participants performed three continuous 11-min blocks of a mental-workload task (3-back) and an oddball version of this task. Also, heart-rate variability (HRV), cognitive-performance scores, and subjective measure of mental load (NASA-TLX) were determined. IOP was taken before each block and afterwards as well as after recovery from mental tasks. We found that IOP increased during heavy mental workloads (p < 0.01). Consistent with this finding, the autonomic control (HRV) and the cognitive performance were significantly lower (p < 0.045, and p < 0.01, respectively), and the NASA-TLX scores were higher during the 3-back task (p < 0.01). We conclude that IOP is sensitive to mental workload, and it could provide a novel neuroergonomic tool to assess mental workload. Our study highlights a potential association between IOP and the nervous system's state of activation.

Stopping ability in younger and older adults: Behavioral and event-related potential.

This study examines age-related differences in inhibitory control as measured by stop-signal performance. The participants were 24 adults aged 20-30 years and 24 older adults aged 61-76 years. The task blocks were pure choice reaction-time blocks, global stop-signal blocks (with an auditory stop signal), and selective stop-signal blocks (with valid and invalid stop signals). There was a decline in reactive inhibitory control for the older group reflected by greater stop-signal reaction times and reduced P3 peak amplitudes in both global and selective stop-signal task blocks. The decreased reactive inhibitory control might result from speed-accuracy tradeoffs. Conversely, no age-related decline in proactive inhibitory control was observed. This was reflected by slower response times (RTs) and reduced P3 peak amplitudes during GO trials in blocks with stop-signals relative to those in blocks of pure choice reaction-time tasks, and in which the RT and amplitude differences were similar between groups. The results further show age-related compensation responses associated with proactive inhibition, such as increased activation at the frontal site among older participants, resulting in no differences in P3 peak amplitudes between electrode sites, and smaller differences at the Fz site than other sites compared with younger adults. For older adults, the P3 peak amplitude at the Fz site was significantly correlated with the RT of proactive inhibitory control. This shows that larger RT differences were associated with larger reductions in P3 peak amplitudes in the stop-signal blocks relative to the pure choice blocks. These results appear to support age-related compensation hypotheses.

Visual cue-specific craving is diminished in stressed smokers

ABSTRACTBackground: Craving among smokers is increased by stress and exposure to smoking-related visual cues. However, few experimental studies have tested both elicitors concurrently and considered how exposures may interact to influence craving. Objective: The current study examined craving in response to stress and visual cue exposure, separately and in succession, in order to better understand the relationship between craving elicitation and the elicitor. Method: Thirty-nine smokers (21 males) who forwent smoking for 30 minutes were randomized to complete a stress task and a visual cue task in counterbalanced orders (creating the experimental groups); for the cue task, counterbalanced blocks of neutral, motivational control, and smoking images were presented. Self-reported craving was assessed after each block of visual stimuli and stress task, and after a recovery period following each task. Results: As expected, the stress and smoking images generated greater craving than neutral or motivational control images (p < .001). Interactions indicated craving in those who completed the stress task first differed from those who completed the visual cues task first (p < .05), such that stress task craving was greater than all image type craving (all p’s < .05) only if the visual cue task was completed first. Conversely, craving was stable across image types when the stress task was completed first. Conclusions: Findings indicate when smokers are stressed, visual cues have little additive effect on craving, and different types of visual cues elicit comparable craving. These findings may imply that once stressed, smokers will crave cigarettes comparably notwithstanding whether they are exposed to smoking image cues.

Foreknowledge of an impending startling stimulus does not affect the proportion of startle reflexes or latency of StartReact responses.

During a simple reaction time (RT) task, movements can be initiated early and involuntarily through presentation of a loud startling acoustic stimulus (SAS), a phenomenon termed the StartReact effect. In order to infer that activity in startle-related structures led to the early response triggering, it is important to observe a concurrent startle reflex in sternocleidomastoid. It is generally accepted that to consistently elicit a startle reflex, the SAS must be both intense and unpredictable. However, it remains unclear what effect explicit foreknowledge of an impending SAS has on the effectiveness of a SAS to elicit a startle reflex when preparing a motor response. To test this, participants completed two separate blocks of a simple RT task (counterbalanced order), where the control auditory go-signal was replaced with a SAS on 20% of trials. In an unwarned block, knowledge of the trial type (SAS vs. control) was not provided in advance, while in a warned block, the trial type was forewarned. Results revealed that while foreknowledge of an impending SAS reduced the magnitude of the startle reflex, it did not affect the proportion of startle reflexes elicited or the magnitude of the StartReact effect. An increase in control trial RT was observed during the unwarned block, but only when it was performed first. These results indicate that preparation of a motor response leads to sufficiently increased activation in startle-related neural structures such that even with explicit knowledge of an upcoming SAS, participants are unable to proactively gate the upcoming sensory input.

Efficient computation of the likelihood expansions for diffusion models

ABSTRACTClosed-form likelihood expansion is an important method for econometric assessment of continuous-time models driven by stochastic differential equations based on discretely sampled data. However, practical applications for sophisticated models usually involve significant computational efforts in calculating high-order expansion terms in order to obtain the desirable level of accuracy. We provide new and efficient algorithms for symbolically implementing the closed-form expansion of the transition density. First, combinatorial analysis leads to an alternative expression of the closed-form formula for assembling expansion terms from that currently available in the literature. Second, as the most challenging task and central building block for constructing the expansions, a novel analytical formula for calculating the conditional expectation of iterated Stratonovich integrals is proposed and a new algorithm for converting the conditional expectation of the multiplication of iterated Stratonovich integrals to a linear combination of conditional expectation of iterated Stratonovich integrals is developed. In addition to a procedure for creating expansions for a nonaffine exponential Ornstein–Uhlenbeck stochastic volatility model, we illustrate the computational performance of our method.

Mental effort in adolescents with ADHD

Mental effort plays an important role in theoretical models of ADHD; it is central to both motivational and cognitive-energetic accounts, but it has been underspecified and under-examined empirically. It could however, provide the missing link between task performance of difficult and challenging tasks requiring cognitive control, and the effects of extrinsic rewards on performance in ADHD. In this exploratory study we examined two putative effort-related deficits in ADHD; First, impairments in the ability to apply effort and second, alterations in effort-related decision making due to an altered cost-benefit analysis relating to the application of effort. For this purpose, we examined 1) performance on an N-back task with five levels of difficulty (1-, 2-, 3-, 4-, 5-back) and choice behavior on a subsequent effort discounting task, 2) pupil dilation during the N-back task, and 3) subjective measures of mental demand and effort application during the N-back task. Fifteen boys with ADHD and 16 controls (aged 12-17 years) participated in this study. Results showed that with increasing level of N-back difficulty, performance deteriorated, and participants with ADHD performed significantly worse than controls, independent of level of difficulty. In the effort-discounting task, however, no main effect of group was found, indicating that adolescents with ADHD did not devalue effort-related rewards more than controls. This suggests that they are not more effort averse than controls. The overall pattern of pupil responses during the N-back blocks looked similar for ADHD and control participants: there was an initial increase in pupil dilation in the first 3-6 trials of a task block, after which a gradual decline in pupil response occurred back to baseline. In the control group, the peak of this pupil dilation increased with level of difficulty up to 3-back, while in the ADHD group such an effect was absent. Finally, groups did not differ in the subjective experience of the mental demand of the different levels of the N-back task, nor in effort application. Together, these results suggest that performance decrements in ADHD in a working memory task such as the task used here might be related to a suboptimal application of mental effort, which is not reflected in subjective experiences, and subsequently does not appear to lead to an altered cost-benefit analysis related to the application of effort.

Specific Deficit in Implicit Motor Sequence Learning following Spinal Cord Injury.

BackgroundPhysical and psychosocial rehabilitation following spinal cord injury (SCI) leans heavily on learning and practicing new skills. However, despite research relating motor sequence learning to spinal cord activity and clinical observations of impeded skill-learning after SCI, implicit procedural learning following spinal cord damage has not been examined.ObjectiveTo test the hypothesis that spinal cord injury (SCI) in the absence of concomitant brain injury is associated with a specific implicit motor sequence learning deficit that cannot be explained by depression or impairments in other cognitive measures.MethodsTen participants with SCI in T1-T11, unharmed upper limb motor and sensory functioning, and no concomitant brain injury were compared to ten matched control participants on measures derived from the serial reaction time (SRT) task, which was used to assess implicit motor sequence learning. Explicit generation of the SRT sequence, depression, and additional measures of learning, memory, and intelligence were included to explore the source and specificity of potential learning deficits.ResultsThere was no between-group difference in baseline reaction time, indicating that potential differences between the learning curves of the two groups could not be attributed to an overall reduction in response speed in the SCI group. Unlike controls, the SCI group showed no decline in reaction time over the first six blocks of the SRT task and no advantage for the initially presented sequence over the novel interference sequence. Meanwhile, no group differences were found in explicit learning, depression, or any additional cognitive measures.ConclusionsThe dissociation between impaired implicit learning and intact declarative memory represents novel empirical evidence of a specific implicit procedural learning deficit following SCI, with broad implications for rehabilitation and adjustment.

Mid-Task Break Improves Global Integration of Functional Connectivity in Lower Alpha Band.

Numerous efforts have been devoted to revealing neurophysiological mechanisms of mental fatigue, aiming to find an effective way to reduce the undesirable fatigue-related outcomes. Until recently, mental fatigue is thought to be related to functional dysconnectivity among brain regions. However, the topological representation of brain functional connectivity altered by mental fatigue is only beginning to be revealed. In the current study, we applied a graph theoretical approach to analyse such topological alterations in the lower alpha band (8~10 Hz) of EEG data from 20 subjects undergoing a two-session experiment, in which one session includes four successive blocks with visual oddball tasks (session 1) whereas a mid-task break was introduced in the middle of four task blocks in the other session (session 2). Phase lag index (PLI) was then employed to measure functional connectivity strengths for all pairs of EEG channels. Behavior and connectivity maps were compared between the first and last task blocks in both sessions. Inverse efficiency scores (IES = reaction time/response accuracy) were significantly increased in the last task block, showing a clear effect of time-on-task in participants. Furthermore, a significant block-by-session interaction was revealed in the IES, suggesting the effectiveness of the mid-task break on maintaining task performance. More importantly, a significant session-independent deficit of global integration and an increase of local segregation were found in the last task block across both sessions, providing further support for the presence of a reshaped topology in functional brain connectivity networks under fatigue state. Moreover, a significant block-by-session interaction was revealed in the characteristic path length, small-worldness, and global efficiency, attributing to the significantly disrupted network topology in session 1 in comparison of the maintained network structure in session 2. Specifically, we found increased nodal betweenness centrality in several channels resided in frontal regions in session 1, resembling the observations of more segregated global architecture under fatigue state. Taken together, our findings provide insights into the substrates of brain functional dysconnectivity patterns for mental fatigue and reiterate the effectiveness of the mid-task break on maintaining brain network efficiency.

To Be Bored or Not To Be Bored—How Task‐Related Boredom Influences Creative Performance

AbstractIn the current society, boredom has a bad reputation. Among others, one reason is that boredom is a negative predictor for cognitive performance due to the detrimental effects on attention and engagement. Recently, however, the negative reputation has been challenged by studies showing that boredom seems to promote creativity. However, those studies examined the influence of incidental boredom on apparently unrelated creativity tasks, leaving it open to question what happens when the individual gets bored by the task itself. To examine this issue, participants performed six blocks of a creativity task, and we measured creativity performance and experienced boredom across blocks. Results showed that boredom increased in parallel with fluency performance. However, more detailed analyses showed that the fluency increase was not brought about by the increase in boredom but was fully accounted for by the effect of increased task practice. When controlling for practice effects, results revealed that boredom actually impaired fluency. Such a finding supports the view that boredom has a negative impact on cognitive performance and underlines the necessity for changes in educational settings to prevent boredom.

The impact of simulated MRI scanner background noise on visual attention processes as measured by the EEG.

Environmental noise is known to affect personal well-being as well as cognitive processes. Besides daily life, environmental noise can also occur in experimental research settings, e.g. when being in a magnetic resonance scanner. Scanner background noise (SBN) might pose serious confounds for experimental findings, even when non-auditory settings are examined. In the current experiment we tested if SBN alters bottom-up and top-down related processes of selective visual attention mechanisms. Participants completed two blocks of a visual change detection task, one block in silence and one block under SBN exposure. SBN was found to decrease accuracy in measures of visual attention. This effect was modulated by the temporal occurrence of SBN. When SBN was encountered in the first block, it prevented a significant improvement of accuracy in the second block. When SBN appeared in the second block, it significantly decreased accuracy. Neurophysiological findings showed a strong frontal positivity shift only when SBN was present in the first block, suggesting an inhibitory process to counteract the interfering SBN. Common correlates of both top-down and bottom-up processes of selective visual attention were not specifically affected by SBN exposure. Further research appears necessary to entirely rule out confounds of SBN in assessing visual attention.

Anxiety Patients Show Reduced Working Memory Related dlPFC Activation During Safety and Threat.

Anxiety patients exhibit deficits in cognitive tasks that require prefrontal control of attention, including those that tap working memory (WM). However, it is unclear whether these deficits reflect threat-related processes or symptoms of the disorder. Here, we distinguish between these hypotheses by determining the effect of shock threat versus safety on the neural substrates of WM performance in anxiety patients and healthy controls. Patients, diagnosed with generalized and/or social anxiety disorder, and controls performed blocks of an N-back WM task during periods of safety and threat of shock. We recorded blood-oxygen-level dependent (BOLD) activity during the task, and investigated the effect of clinical anxiety (patients vs. controls) and threat on WM load-related BOLD activation. Behaviorally, patients showed an overall impairment in both accuracy and reaction time compared to controls, independent of threat. At the neural level, patients showed less WM load-related activation in the dorsolateral prefrontal cortex, a region critical for cognitive control. In addition, patients showed less WM load-related deactivation in the ventromedial prefrontal cortex and posterior cingulate cortex, which are regions of the default mode network. Most importantly, these effects were not modulated by threat. This work suggests that the cognitive deficits seen in anxiety patients may represent a key component of clinical anxiety, rather than a consequence of threat.

Does Varying Attentional Focus Affect Skill Acquisition in Children? A Comparison of Internal and External Focus Instructions and Feedback

Recently, researchers have concluded that motor skill performance is enhanced when learners adopt an external attentional focus, compared to adopting an internal focus. We extended the line of inquiry to children and examined if skill learning in children was differentially affected by providing instructions and feedback that direct attentional focus internally versus externally and if the effect of attentional focus varied between younger and older children. Forty-eight children in two age groups (5–8 years old and 9–12 years old) were randomly assigned to either an internal attentional focus group or an external attentional focus group. Participants completed three 10-trial acquisition blocks of a shuffleboard accuracy task, followed by retention and transfer tests. There was no significant difference between internal and external focus groups, though older children performed significantly better than younger ones did, and all groups improved with practice. These results suggest that skill learning in children improves with task-based instruction and practice, regardless of the direction of attentional focus. More research is needed on children and attentional focus to determine whether they, and possibly other beginners, learn better with an internal or external focus of attention.

Electrifying the lexical decision

The current research utilizes lexical decision within an oddball ERP paradigm to study early lexical processing. Nineteen undergraduate students completed four blocks of the oddball lexical decision task (Nonword targets among Words, Word targets among Nonwords, Word targets among Pseudowords, and Pseudoword targets among Words). We observed a reliable P3 ERP component in conditions where the distinction between rare and frequent trials could be made solely based on lexical status (Words among Nonwords and Nonwords among Words). We saw a reliable P3 to rare words among frequent pseudowords, but no P3 was observed when participants were asked to detect pseudowords in the context of frequent word stimuli. We argue that this observed modulation of the P3 results is consistent with psycholinguistic literature that suggests that two criteria are available during lexical access when performing a lexicality judgement, a non-lexical criterion that relies on global activation at the word level and a lexical criterion that relies on activation of a lexical representation (Coltheart, Rastle, Perry, Langdon, &amp; Ziegler, 2001; Grainger &amp; Jacobs, 1996).

Is There a Cognitive Advantage for Spanish Heritage Bilinguals? A First Look

We report the findings from an ongoing study on the relationship between bilinguals’ language experience and cognitive control. Previous research suggests that early bilingualism exerts an advantage on executive control, possibly due to the cognitive requirements involved in the daily juggling of two languages (Adesope, Lavin, Thompson, &amp; Ungerleider, 2010). However, other researchers also have argued against a cognitive control advantage in bilinguals (Hilchey &amp; Klein, 2011). It remains unclear whether cognitive benefits hold true for bilinguals across different contexts, given differences in sociolinguistic and socioeducational settings that shape individual bilingualism. In the current study, following Costa, Hernández and Sebastián-Gallés (2008) who tested Catalan-Spanish bilinguals, young adult simultaneous heritage bilinguals and late classroom emerging bilinguals of Spanish in the U.S. completed three blocks of the Attentional Network Task (ANT) (Fan, McCandliss, Sommer, Raz, &amp; Posner, 2002) to gauge executive control abilities. Results for the executive network component of the ANT reveal no significant differences between the two bilingual groups, although the descriptive data trend suggests that HL bilinguals experienced less difficulty in solving conflicting information and demonstrated fewer switching costs between trials. These first findings imply that the bilingual advantage is not replicated across contexts, and that socioeducational practices determine individual patterns of language use, which in turn leads to variation in cognitive outcomes.

The Effects of Varying Break Length on Attention and Time on Task.

We aimed to discover how varying the length of task breaks would affect the time-on-task effect in subsequent testing periods. An important means of preventing errors and accidents caused by mental fatigue and time on task is to intersperse rest intervals within long work periods. Most studies of rest pauses to date have examined their effects in real-world tasks and settings, and their subtler effects on behavior, as measurable by laboratory paradigms, are not well understood. We studied a group of 71 participants as they completed a 1-hr auditory oddball task with two rest opportunities. Rest intervals were 1, 5, or 10 min long. Improvements in reaction time were significantly positively associated with length of the rest break. However, longer breaks were also associated with steeper decrements in performance in the subsequent task block. Across individuals, the amount of immediate improvement correlated with the extent of later decline. Our results support a resource/effort-allocation model of fatigue, whereby longer breaks bias participants toward greater effort expenditure on resumption of the task when cognitive resources may not have been fully replenished. These findings may have implications for the refinement of work-rest schedules in industries where time-on-task degradation in performance is an important concern.