Effects Of Task Difficulty Research Articles

Effects of Task Difficulty on Neural Processes Underlying Semantics: An Event-Related Potentials Study.

Purpose Improving the ability to listen efficiently in noisy environments is a critical goal for hearing rehabilitation. However, understanding of the impact of difficult listening conditions on language processing is limited. The current study evaluated the neural processes underlying semantics in challenging listening conditions. Method Thirty adults with normal hearing completed an auditory sentence processing task in 4-talker babble. Event-related brain potentials were elicited by the final word in high- or low-context sentences, where the final word was either highly expected or not expected, followed by a 4-alternative forced-choice response with either longer (1,000 ms), middle (700 ms), or shorter (400 ms) response time deadlines (RTDs). Results Behavioral accuracy was reduced, and reactions times were faster for shorter RTDs. N400 amplitudes, reflecting ease of lexical access, were larger when elicited by target words in low-context sentences followed by shorter compared with longer RTDs. Conclusions These results reveal that more neural resources are allocated for semantic processing/lexical access when listening difficulty increases. Differences between RTDs may reflect increased attentional allocation for shorter RTDs. These findings suggest that situational listening demands can impact the demands for cognitive resources engaged in language processing, which could significantly impact listener experiences across environments.

Standing task difficulty related increase in agonist-agonist and agonist-antagonist common inputs are driven by corticospinal and subcortical inputs respectively

In standing, coordinated activation of lower extremity muscles can be simplified by common neural inputs to muscles comprising a functional synergy. We examined the effect of task difficulty on common inputs to agonist-agonist (AG-AG) pairs supporting direction specific reciprocal muscle control and agonist-antagonist (AG-ANT) pairs supporting stiffness control. Since excessive stiffness is energetically costly and limits the flexibility of responses to perturbations, compared to AG-ANT, we expected greater AG-AG common inputs and a larger increase with increasing task difficulty. We used coherence analysis to examine common inputs in three frequency ranges which reflect subcortical/spinal (0–5 and 6–15 Hz) and corticospinal inputs (6–15 and 16–40 Hz). Coherence was indeed higher in AG-AG compared to AG-ANT muscles in all three frequency bands, indicating a predilection for functional synergies supporting reciprocal rather than stiffness control. Coherence increased with increasing task difficulty, only in AG-ANT muscles in the low frequency band (0–5 Hz), reflecting subcortical inputs and only in AG-AG group in the high frequency band (16–40 Hz), reflecting corticospinal inputs. Therefore, common neural inputs to both AG-AG and AG-ANT muscles increase with difficulty but are likely driven by different sources of input to spinal alpha motor neurons.

Concentrative (Sahaj Samadhi) meditation expands subjective time.

Previous studies have demonstrated the effect of mindfulness meditation on subjective experience of time. Task difficulty influenced subjective experience of time with larger subjective expansion of time among meditators with a more difficult task. It is not clear whether the effect would generalize to concentrative meditation training. Hence, in the present study, using a temporal bisection task, we investigated the effect of task difficulty (with two discrimination ratios of short and long durations) on subjective experience of time in long-term concentrative (Sahaj Samadhi) meditators and non-meditators. The results provide evidence for subjective expansion of time among long-term concentrative meditators, which is in line with the previous findings with mindfulness meditators. Similar to the earlier study with mindfulness meditators, we also found expansion of time for concentrative meditators only in the difficult task condition where attentional demands are high and less attentional resources are available for processing time. The findings suggest that subjective expansion of time is most likely a general effect of attentional enhancement irrespective of the type of meditation practice.

Differential control of task and null space variability in response to changes in task difficulty when learning a bimanual steering task.

The presence of motor redundancy means that movement variability can be split into a 'task-space' component that affects task performance, and a 'null space' component which has no effect on task performance. While the control of task-space variability during learning is essential, because it is directly linked to performance, how the nervous system controls null space variability during learning has not been well understood. One factor that has been hypothesized to govern the change in null space variability with learning is task difficulty, but this has not been directly tested. Here, we examined how task difficulty influences the change in null space variability with learning. Healthy, college-aged participants (N = 36) performed a bimanual steering task, where they steered a cursor through a smooth W-shaped track of a certain width as quickly as possible while attempting to keep the cursor within the track. Task difficulty was altered by changing the track width and participants were split into one of the three groups based on the track width that they practiced on-wide, narrow, or progressive (where the width of the track progressively changed from wide to narrow over practice). The redundancy in this task arose from the fact that the position of the cursor was defined as the average position of the two hands. Results showed that movement time depended on task difficulty, but all groups were able to decrease their movement time with practice. Learning was associated with a reduction in null space variability in all groups, but critically, there was no effect of task difficulty. Further analyses showed that while the task-space variability showed an expected speed-accuracy tradeoff with movement time, the null space variability showed a qualitatively different pattern. These results suggest differential control of task and null space variability in response to changes in task difficulty with learning, and may reflect a strong preference to minimize overall movement variability during learning.

LED 조명의 조도와 과제난이도가 장기기억에 미치는 영향

LED 조명의 조도와 과제난이도가 장기기억에 미치는 영향

Potential Mechanisms for the Ketamine-Induced Reduction of P3b Amplitudes.

In specific dosages, the N-methyl-D-aspartate receptor (NMDA) antagonist ketamine can be used to model transient psychotic symptoms in healthy individuals that resemble those of schizophrenia. Ketamine administration also temporarily impairs cognitive functions, which can be studied by event-related potentials (ERPs). ERPs also allow dissecting what stages of information processing are affected by ketamine and what stages remain functional. For tasks requiring the differentiation of targets and non-targets, it has repeatedly been shown that ketamine administration in healthy individuals leads to decreased amplitudes of the ERP component P3b in response to target stimuli. However, it could be argued that this ketamine-induced P3b reduction is the consequence of an increased difficulty to differentiate targets from non-targets, primarily mediated by ketamine's psychotomimetic rather than pharmacological effects. The current review of ERP studies seeks to clarify the issue whether P3b effects of ketamine may indeed be explained as the consequence of an experienced increase in task difficulty or whether alternative mechanisms are perhaps more plausible. The review first summarizes the effects of task difficulty on ERP components related to intentional stimulus categorization (P3b), involuntary attention switches to distractors (P3a), as well as sensory processing (P1, N1). Secondly, the ERP effects of task difficulty are contrasted with those observed in ketamine studies in healthy individuals. Findings show that P3b amplitudes are consistently diminished by an increased task difficulty, as well as after ketamine administration. In contrast and as most important difference, increased task difficulty leads to increased P3a amplitudes to distractors presented in same modality as targets, whereas ketamine leads to reduced P3a amplitudes for such distractors. This dissociation indicates that the decreased P3b amplitudes after ketamine cannot be explained by a drug-induced increase in task difficulty. The conjoint reductions of P3a and P3b amplitudes instead suggest that working memory operations, in particular working memory updating are impaired after ketamine, which is in line with previous behavioral findings.

Electrophysiological Correlates of the Effect of Task Difficulty on Inhibition of Return.

Inhibition of return (IOR) refers to slower responses to targets that occur at a previously attended location than to those at control locations. Previous studies on the impact of task difficulty on IOR have shown conflicting results. However, these studies failed to match low-level characteristics of stimuli (e.g., size, color, and luminance) across difficulty levels, and so might have confounded the effect of task difficulty with that of stimulus characteristics. Hence, whether and how task difficulty modulates IOR remain largely unknown. This study utilized the event-related potentials (ERPs) technique in combination with a cue-target paradigm to tackle this question. Task difficulty was manipulated by changing the position of a gap in a rectangle stimulus, while stimulus size, color, and luminance were precisely matched. IOR was observed in reaction times across all difficulty levels but was found in accuracy at the medium level only. The modulation effect of task difficulty on IOR was also evident in the N1 and P2 ERP components, which showed significantly weaker IOR effects at the medium difficulty level than at the easy and hard levels. It is suggested that the modulation of IOR by task difficulty involves both perceptual and post-perceptual processes.

Is overconfidence a motivated bias? Experimental evidence.

Are overconfident beliefs driven by the motivation to view oneself positively? We test the relationship between motivation and overconfidence using two distinct, but often conflated measures: better-than-average (BTA) beliefs and overplacement. Our results suggest that motivation can indeed affect these faces of overconfidence, but only under limited conditions. Whereas BTA beliefs are inflated by motivation, introducing some specificity and clarity to the standards of assessment (Experiment 1) or to the trait's definition (Experiments 2 and 3) reduces or eliminates this bias in judgment overall. We find stronger support for a cognitive explanation for overconfidence, which emphasizes the effect of task difficulty. The difficulty of possessing a desirable trait (Experiment 4) or succeeding on math and logic problems (Experiment 5) affects self-assessment more consistently than does motivation. Finally, we find the lack of an objective standard for vague traits allows people to create idiosyncratic definitions and view themselves as better than others in their own unique ways (Experiment 6). Overall, the results suggest motivation's effect on BTA beliefs is driven more by idiosyncratic construals of assessment than by self-enhancing delusion. They also suggest that by focusing on vague measures (BTA rather than overplacement) and vague traits, prior research may have exaggerated the role of motivation in overconfidence. (PsycINFO Database Record (c) 2018 APA, all rights reserved).

Contrasting the Effects of Task Difficulty and Perceptual Load on Auditory Detection Sensitivity in Individuals with Autism.

To test a central assumption of the increased perceptual capacity account in individuals with Autism Spectrum Disorder (ASD), the effects of perceptual load and target-stimulus degradation on auditory detection sensitivity were contrasted. Fourteen adolescents with ASD and 16 neurotypical controls performed a visual letter search task under three conditions: low perceptual load, high perceptual load and low perceptual load with a degraded target while simultaneously detecting an auditory tone in noise. For both participants with ASD and neurotypical controls, increasing perceptual load and target degradation increased task difficulty as indexed by reaction times and accuracy. However, only increasing perceptual load reduced subsequent auditory detection sensitivity. The study confirms that perceptual load, and not task difficulty, modulates selective attention in ASD.

The Role of Task Difficulty in Learning a Visuomotor Skill.

Task difficulty affects the amount of interpretable information from a task, which is thought to interfere with motor learning. However, it is unclear whether task difficulty in itself is a stimulus for motor learning because the experimental evidence is mixed in support of the optimal challenge point framework that predicts one specific level of task difficulty to produce the greatest magnitude of motor learning. We determined the effects of functional task difficulty on motor skill acquisition, retention, and transfer. Healthy young participants (N = 36) learned a mirror star-tracing task at a low, medium, or hard difficulty level defined by the bandwidth of the star. We measured skill acquisition, retention, and transfer to untrained difficulty levels, as well as the perceived mental workload during the task. Task difficulty affected motor performance, but did not affect motor learning and transfer. For the groups that practiced the task at the medium and hard but not at the low difficulty level, initial skill level correlated with the magnitude of learning. The optimal challenge point framework does not capture the complex relationship between task difficulty and motor learning. Previously reported effects of task difficulty on the magnitude of motor learning are probably mediated by perceived mental workload. Task difficulty did not affect the magnitude of visuomotor skill learning but it affected how learning occurred. The data have implications on how athletes learn new motor skills and patients relearn injury-impaired motor skills during rehabilitation.

Virtual Reality Experiments with Physiological Measures.

Virtual reality (VR) experiments are increasingly employed because of their internal and external validity compared to real-world observation and laboratory experiments, respectively. VR is especially useful for geographic visualizations and investigations of spatial behavior. In spatial behavior research, VR provides a platform for studying the relationship between navigation and physiological measures (e.g., skin conductance, heart rate, blood pressure). Specifically, physiological measures allow researchers to address novel questions and constrain previous theories of spatial abilities, strategies, and performance. For example, individual differences in navigation performance may be explained by the extent to which changes in arousal mediate the effects of task difficulty. However, the complexities in the design and implementation of VR experiments can distract experimenters from their primary research goals and introduce irregularities in data collection and analysis. To address these challenges, the Experiments in Virtual Environments (EVE) framework includes standardized modules such as participant training with the control interface, data collection using questionnaires, the synchronization of physiological measurements, and data storage. EVE also provides the necessary infrastructure for data management, visualization, and evaluation. The present paper describes a protocol that employs the EVE framework to conduct navigation experiments in VR with physiological sensors. The protocol lists the steps necessary for recruiting participants, attaching the physiological sensors, administering the experiment using EVE, and assessing the collected data with EVE evaluation tools. Overall, this protocol will facilitate future research by streamlining the design and implementation of VR experiments with physiological sensors.

Effect of reading intervention and task difficulty on orthographic and phonological reading systems in the brain

Children with poor reading skills have differences in brain function when compared to typically-developing readers, and there may also be changes in the brain following reading intervention. However, most functional imaging studies focus on phonological reading tasks with one level of task difficulty. The purpose of this study was to compare good and poor readers on functional magnetic resonance imaging (fMRI) tasks of orthography (spelling) and phonology (rhyming) before and after 3 months of school-based intervention. These tasks were also modulated by task difficulty based on printed word frequency. The results showed that primarily left hemisphere regions were activated for the spelling and rhyming tasks, and poor readers showed a pattern of increased activation in bilateral inferior frontal, bilateral insula, right parietal, and left cerebellum following intervention. Activity in left pars triangularis and right parietal regions were associated with gains in decoding skills. Intervention effects appeared across blocks of easy and difficult words, except for the right parietal cortex. In this region, poor readers had greater activity on the easy word blocks after intervention, which indicates that there was increased recruitment of the right parietal cortex for relatively easy words. These results indicate that effects of intervention may be more evident on phonological tasks in comparison to orthographic tasks, and some of these effects may be modulated by relative task difficulty.

The effect of task difficulty on decision-making

The aim was to determine whether there are differences between groups in jumping to conclusions and the number of beads required to make a decision based on task difficulty. An assessment was made of 19 patients with non-affective psychosis, 19 with obsessive–compulsive disorder (OCD), and 19 healthy controls. The Beads Task scale was used in its two versions. Patients with non-affective psychosis jumped to conclusions. There was significant interaction between group and task difficulty. Increased difficulty of the task did not affect the number of beads patients with non-affective psychosis or OCD needed to make their decision. However, healthy controls needed to see more beads before they could make a decision in the hard test than in the easy one. Patients with non-affective psychosis jump to conclusions, but neither this group nor the OCD patients benefit from the changes in task difficulty when making their decisions.

Effect of task difficulty on blood-oxygen-level-dependent signal: A functional magnetic resonance imaging study in a motion discrimination task.

There is much evidence that neural activity in the human brain is modulated by task difficulty, particularly in visual, frontal, and parietal cortices. However, some basic psychophysical tasks in visual perception do not give rise to this expected effect, at least not in the visual cortex. In the current study, we used functional magnetic resonance imaging (fMRI) to record brain activity while systematically manipulating task difficulty in a motion discrimination task, by varying the angular difference between the motion direction of random dots and a reference direction. We used both a blocked and an event-related design, and presented stimuli in both central and peripheral vision. The behavioral psychometric function, across angular differences of 3°, 9°, 15°, or 80°, spanned the full response range, as expected. The mean blood oxygen level dependent (BOLD) signals were also correlated within-participants between the blocked and event-related designs, across all brain areas tested. Within the visual cortex, the voxel response patterns correlated more within-conditions (e.g., 3° and 3°) than between-conditions (e.g., 3° and 9°), in both designs, further attesting to the reasonable quality of the BOLD data. Nevertheless, the BOLD-o-metric functions (i.e., BOLD activity as a function of task difficulty) were flat in the whole-brain and region-of-interest (ROI) analyses, including in the visual cortex, the parietal cortex, in both designs, and in foveal and peripheral visual fields alike. Indeed, there was little difference between BOLD activity during the 3° and 80° conditions. Some suggestive evidence of difficulty modulation was revealed only in the superior and inferior frontal gyri for the blocked design. We conclude that, in motion discrimination, there is no systematic BOLD modulation that accompanies the standard psychometric function across different hierarchies of cortical areas, except for the frontal lobe of the brain.

Effects of Task Difficulty on Kinematics and Task Performance during Walking Workstation Use

ABSTRACT Although walking workstations do not seem to compromise task performance despite altered gait kinematics, current evidence stems from evaluations of relatively simple tasks that do not reflect typical work duties. Purpose This study aimed to examine the effects of simple cognitive (SC) and complex cognitive (CC) tasks on gait kinematics during walking workstation use in comparison to baseline walking. Methods Three-dimensional kinematic data of the lower extremity and trunk were collected while walking during baseline, SC, and CC conditions, with each condition performed at a self-selected velocity. Kinematic data were time normalized to 100% of the gait cycle and divided into subphases for analysis. Differences in walking velocity (baseline vs SC/CC) and task performance (SC vs CC) were tested using paired-samples t-test (α = 0.05). Kinematic data were tested for differences between baseline and SC, baseline and CC, and SC and CC using a point-to-point model statistic analysis (α = 0.05) at the single-subject level. Results Walking velocity was not different between baseline and SC/CC (1.10 ± 0.25 m·s−1, baseline; 1.11 ± 0.26 m·s−1, SC/CC; P = 0.409), nor was task performance time different between SC and CC (81.1 ± 25.6 s, SC; 87.6 ± 17.7 s, CC; P = 0.394). Similar percentages of differences were detected across participants during each gait subphase for all lower extremity joint angles during SC and CC when compared with baseline. A greater percentage of differences were observed in trunk angles during SC than during CC when compared with baseline. Conclusions Results indicate that trunk kinematics are influenced by task difficulty during walking workstation use, although lower extremity kinematics are not affected regardless of task difficulty. Thus, walking workstations do not compromise task performance during work-related tasks and walking safety does not seem threatened by tasks of greater difficulty.

Alterations in the cortical control of standing posture during varying levels of postural threat and task difficulty.

Cortical excitability increases during the performance of more difficult postural tasks. However, it is possible that changes in postural threat associated with more difficult tasks may in themselves lead to alterations in the neural strategies underlying postural control. Therefore, the purpose of this study was to examine whether changes in postural threat are responsible for the alterations in corticospinal excitability and short-interval intracortical inhibition (SICI) that occur with increasing postural task difficulty. Fourteen adults completed three postural tasks (supported standing, free standing, or standing on an unstable board) at two surface heights (ground level or 3 m above ground). Single- and paired-pulse magnetic stimuli were applied to the motor cortex to compare soleus (SOL) and tibialis anterior (TA) test motor-evoked potentials (MEPs) and SICI between conditions. SOL and TA test MEPs increased from 0.35 ± 0.29 to 0.82 ± 0.41 mV (SOL) and from 0.64 ± 0.51 to 1.96 ± 1.45 mV (TA), respectively, whereas SICI decreased from 52.4 ± 17.2% to 39.6 ± 15.4% (SOL) and from 71.3 ± 17.7% to 50.3 ± 19.9% (TA) with increasing task difficulty. In contrast to the effects of task difficulty, only SOL test MEPs were smaller when participants stood at high (0.49 ± 0.29 mV) compared with low height (0.61 ± 0.40 mV). Because the presence of postural threat did not lead to any additional changes in the excitability of the motor corticospinal pathway and intracortical inhibition with increasing task difficulty, it seems unlikely that alterations in perceived threat are primarily responsible for the neurophysiological changes that are observed with increasing postural task difficulty. NEW & NOTEWORTHY We examined how task difficulty and postural threat influence the cortical control of posture. Results indicated that the motor corticospinal pathway and intracortical inhibition were modulated more by task difficulty than postural threat. Furthermore, because the presence of postural threat during the performance of various postural tasks did not lead to summative changes in motor-evoked potentials, alterations in perceived threat are not responsible for the neurophysiological changes that occur with increasing postural task difficulty.

Individual differences in stop-related activity are inflated by the adaptive algorithm in the stop signal task.

Research using the Stop Signal Task employing an adaptive algorithm to accommodate individual differences often report inferior performance on the task in individuals with ADHD, OCD, and substance use disorders compared to non-clinical controls. Furthermore, individuals with deficits in inhibitory control tend to show reduced neural activity in key inhibitory regions during successful stopping. However, the adaptive algorithm systematically introduces performance-related differences in objective task difficulty that may influence the estimation of individual differences in stop-related neural activity. This report examines the effect that these algorithm-related differences have on the measurement of neural activity during the stop signal task. We compared two groups of subjects (n = 210) who differed in inhibitory ability using both a standard fMRI analysis and an analysis that resampled trials to remove the objective task difficulty confound. The results show that objective task difficulty influences the magnitude of between-group differences and that controlling for difficulty attenuates stop-related activity differences between superior and poor inhibitors. Specifically, group differences in the right inferior frontal gyrus, right middle occipital gyrus, and left inferior frontal gyrus are diminished when differences in objective task difficulty are controlled for. Also, when objective task difficulty effects are exaggerated, group differences in stop related activity emerge in other regions of the stopping network. The implications of these effects for how we interpret individual differences in activity levels are discussed.

Effects of work surface and task difficulty on neck–shoulder posture and trapezius activity during a simulated mouse task

Objectives. The purpose of this study is to evaluate the influence of the work surface and task difficulty on the head, upper back and upper arm postures and activity of the descending trapezius during a simulated mouse task. Methods. Healthy female university students (N = 15) were evaluated. The work surface was positioned at elbow height (EH) and above elbow height (AEH) and the task difficulty was set at low (LD) and high (HD) levels. The postures were recorded by inclinometers. Trapezius activity was normalized by the maximum voluntary isometric contraction (MVIC). Results. Significantly higher head flexion was found at EH compared to the AEH condition, with an average difference of 2°–5° at the same difficulty level. The HD task significantly increased head (3°–6°) and upper back flexion (6°–7°) at the same table height. For upper arm elevation and trapezius activation, the AEH condition presented higher upper arm elevation (about 6°–8°) and trapezius activity (0.8–1.4% of MVIC), regardless of the difficulty level of the task. Conclusions. Head posture was influenced by the table height and task difficulty; the upper back posture by high difficulty; and upper arm posture and trapezius activity were only influenced by table height.

The Impact of Auditor Task Difficulty and Audit Quality Indicators on Jurors' Assessments of Audit Quality

ABSTRACTThis study examines the effect of auditor task difficulty on jurors' overall assessment of audit quality following an alleged audit failure (i.e., a restatement) given audit quality indicators (AQIs). We focus on assurance of fair value estimates, a pervasive, difficult-to-audit area. Employing an experiment with prospective jurors, we manipulate auditor task difficulty (moderate or high), input AQI (high or low), and process AQI (high or low). Consistent with expectations from Attribution Theory, we find evidence, as reflected in jurors' assessments of audit quality, that higher task difficulty elicits the salience of external causes for the alleged negative audit outcome (i.e., factors beyond auditors' control) while lower task difficulty induces the salience of internal causes (i.e., factors within auditors' control). Together, our results suggest that jurors recognize the difficulty associated with auditing complex estimates, and in turn adjust their expectations regarding the level of auditor diligence that must be demonstrated, demanding a very high level of diligence (both AQI input and process) for the less difficult task while generally exhibiting lesser demands for the more difficult task. We also find that jurors' audit quality assessments are significantly linked to subsequent evaluations of auditor responsibility and to verdict decisions of auditor negligence.

Psychophysiological reactions to the task difficulty and pacing in subjects with a different anxiety level

A series of experiments were performed with the aim of looking into possible differences of the effects of task difficulty and pacing on some psychophysiological variables in subjects with a low and high level of anxiety. Two equivalent groups of nine subjects (except in anxiety level) performed computer generated numerical and perceptual tasks, where the numerical task had five different difficulty levels, while the perceptual tasks had three. Each of these were perfoemed by every subject under self-paced (unpaced) and paced working conditions. The levels of pacing were equal to the subject's unpaced working level, and 15% higher. The experimental situations were rotated according to the Latin Square principles.During the work on these (primary) tasks, the subject had to perform tapping as the secondary task. Their R-R intervals (sinus arrhythmia) were recorded continuously, together with the tapping intervals. After the completion of the task, the subjects wereasked to estimate the task difficulty on Borg's scale, and to assess it by squeezing a hand dynamometer without looking at its scale.The results showed some differences in the magnitude of certain psychophysiological parameters within the groups, which could be attributed to the effects of task difficulty and pacing.The work-load assessment parameters indicated, that the high anxiety group experienced the tasks and pacing as more strainous, than the low anxiety group. This is especilly true when estimations with a higher mental involvement had to be made. Secondary tasks parameters, however, indicated a smaller residual mental capacity in the group with high anxiety subjects which could represent an explanation of the results on the workload assessment.