Artykuły w czasopismach na temat „Within-task variability”
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Stark, J., C. Pons i O. Kurka. "Within-Task and Across-Task Variability in Agrammatic Narrative Production". Procedia - Social and Behavioral Sciences 61 (październik 2012): 255–56. http://dx.doi.org/10.1016/j.sbspro.2012.10.174.
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Musso, Mandi, Holly James Westervelt, Jeffrey D. Long, Erin Morgan, Steven Paul Woods, Megan M. Smith, Wenjing Lu i Jane S. Paulsen. "Intra-individual Variability in Prodromal Huntington Disease and Its Relationship to Genetic Burden". Journal of the International Neuropsychological Society 21, nr 1 (styczeń 2015): 8–21. http://dx.doi.org/10.1017/s1355617714001076.
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AbstractThe current study sought to examine the utility of intra-individual variability (IIV) in distinguishing participants with prodromal Huntington disease (HD) from nongene-expanded controls. IIV across 15 neuropsychological tasks and within-task IIV using a self-paced timing task were compared as a single measure of processing speed (Symbol Digit Modalities Test [SDMT]) in 693 gene-expanded and 191 nongene-expanded participants from the PREDICT-HD study. After adjusting for depressive symptoms and motor functioning, individuals estimated to be closest to HD diagnosis displayed higher levels of across- and within-task variability when compared to controls and those prodromal HD participants far from disease onset (FICV(3,877)=11.25; p<.0001; FPacedTiming(3,877)=22.89; p<.0001). When prodromal HD participants closest to HD diagnosis were compared to controls, Cohen’s d effect sizes were larger in magnitude for the within-task variability measure, paced timing (−1.01), and the SDMT (−0.79) and paced tapping coefficient of variation (CV) (−0.79) compared to the measures of across-task variability [CV (0.55); intra-individual standard deviation (0.26)]. Across-task variability may be a sensitive marker of cognitive decline in individuals with prodromal HD approaching disease onset. However, individual neuropsychological tasks, including a measure of within-task variability, produced larger effect sizes than an index of across-task IIV in this sample. (JINS, 2015, 21, 8–21)
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Gradin, Victoria, Viktoria-Eleni Gountouna, Gordon Waiter, Trevor S. Ahearn, David Brennan, Barrie Condon, Ian Marshall i in. "Between- and within-scanner variability in the CaliBrain study n-back cognitive task". Psychiatry Research: Neuroimaging 184, nr 2 (listopad 2010): 86–95. http://dx.doi.org/10.1016/j.pscychresns.2010.08.010.
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Malmberg, Lars-Erik, Wee H. T. Lim, Asko Tolvanen i Jari-Erik Nurmi. "Within-student variability in learning experiences, and teachers’ perceptions of students’ task-focus". Frontline Learning Research 4, nr 5 (19.12.2016): 62–82. http://dx.doi.org/10.14786/flr.v4i5.227.
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Jarus, Tal, Emily H. Wughalter i John G. Gianutsos. "Effects of Contextual Interference and Conditions of Movement Task on Acquisition, Retention, and Transfer of Motor Skills by Women". Perceptual and Motor Skills 84, nr 1 (luty 1997): 179–93. http://dx.doi.org/10.2466/pms.1997.84.1.179.
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This experiment was designed to investigate varying conditions of contextual interference within two different conditions of movement tasks during acquisition on the acquisition and retention of a computerized task and transfer to a functional skill. Performance of head movements was conducted under open- or closed-task conditions and with random or blocked schedules of practice. Analysis indicated that learning under the open-task condition resulted in better retention and transfer than the closed-task condition. It is suggested that increasing the within-trial variability in the open-task condition produced a contextual interference effect. In this regard, support for Battig's predictions is provided by the current findings in that the high variability present during the open-task condition was more beneficial for retention and transfer than the low variability present during the closed-task condition. Differences between random and blocked schedules of practice on the retention and transfer data were not statistically significant.
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Gaillard, Audrey, i Isabel Urdapilleta. "Sorting Food Labels and Describing Properties of Categories: Stability of Results between and within Subjects". Psychological Reports 109, nr 1 (sierpień 2011): 187–207. http://dx.doi.org/10.2466/10.13.22.28.pr0.109.4.187-207.
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The purpose of this research is to improve understanding of the consistency of the categorization process in cognitive psychology. To investigate the temporal stability of the categorization process between and within subjects, 100 participants ( M = 22.1 yr., SD = 2.1) were required to sort 65 food labels into groups and to explain their grouping. The sorting and property generation of food labels were compared by conducting two sessions (with a 15-day interval) to assess within-subject variability. Two groups of participants were compared to assess between-subjects variability. The results from the sorting task showed excellent stability between and within subjects. Conversely, the property generation task showed high variability. It is concluded that the tasks involved different types of knowledge. The sorting task appeared to generate good agreement and to involve more stable knowledge. The task of producing properties may involve other mechanisms. This paper discusses the results in light of cognitive and pragmatic theories.
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Miller, Suzanne Bonneau, i Katharine H. Odell. "Age-Related Intraindividual Performance Variability with Practice". International Journal of Aging and Human Development 65, nr 2 (wrzesień 2007): 97–120. http://dx.doi.org/10.2190/ag.65.2.a.
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Fluctuations in cognitive task performance in older individuals have been reported. To examine intraindividual variability as a function of practice, 34 younger and 34 older female participants, aged 20–30 years and 70–82 years, respectively, performed a reading span task 16 times over four sessions. Each individual's recall accuracy was analyzed over the practice trials. It was found that intraindividual variability occurred more frequently in older than younger individuals, and that fluctuations were more frequent in mid to later trials of practice. These findings were interpreted within a resource theory framework as evidence for age-related inefficient cognitive processing with practice.
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Phillips, Christine B., Jerri D. Edwards, Ross Andel i Marcus Kilpatrick. "Daily Physical Activity and Cognitive Function Variability in Older Adults". Journal of Aging and Physical Activity 24, nr 2 (kwiecień 2016): 256–67. http://dx.doi.org/10.1123/japa.2014-0222.
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Physical activity (PA) is believed to preserve cognitive function in older adulthood, though little is known about these relationships within the context of daily life. The present microlongitudinal pilot study explored within- and between-person relationships between daily PA and cognitive function and also examined within-person effect sizes in a sample of community-dwelling older adults. Fifty-one healthy participants (mean age = 70.1 years) wore an accelerometer and completed a cognitive assessment battery for five days. There were no significant associations between cognitive task performance and participants’ daily or average PA over the study period. Effect size estimates indicated that PA explained 0–24% of within-person variability in cognitive function, depending on cognitive task and PA dose. Results indicate that PA may have near-term cognitive effects and should be explored as a possible strategy to enhance older adults’ ability to perform cognitively complex activities within the context of daily living.
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van Dieën, Jaap H., Joris J. M. Dekkers, Vincent Groen, Huub M. Toussaint i Onno G. Meijer. "Within-Subject Variability in Low Back Load in a Repetitively Performed, Mildly Constrained Lifting Task". Spine 26, nr 16 (sierpień 2001): 1799–804. http://dx.doi.org/10.1097/00007632-200108150-00016.
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Mathiassen, Svend Erik, Therése Möller i Mikael Forsman. "Variability in mechanical exposure within and between individuals performing a highly constrained industrial work task". Ergonomics 46, nr 8 (czerwiec 2003): 800–824. http://dx.doi.org/10.1080/0014013031000090125.
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Eakin, Tim, Waneen Spirduso i Karen L. Francis. "Dynamic Variability of Isometric Action Tremor in Precision Pinching". Computational and Mathematical Methods in Medicine 2012 (2012): 1–9. http://dx.doi.org/10.1155/2012/975735.
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Evolutionary development of isometric force impulse frequencies, power, and the directional concordance of changes in oscillatory tremor during performance of a two-digit force regulation task was examined. Analyses compared a patient group having tremor confounding volitional force regulation with a control group having no neuropathological diagnosis. Dependent variables for tremor varied temporally and spatially, both within individual trials and across trials, across individuals, across groups, and between digits. Particularly striking findings were magnitude increases during approaches to cue markers and shifts in the concordance phase from pinching toward rigid sway patterns as the magnitude increased. Magnitudes were significantly different among trace line segments of the task and were characterized by differences in relative force required and by the task progress with respect to cue markers for beginning, reversing force change direction, or task termination. The main systematic differences occurred during cue marker approach and were independent of trial sequence order.
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Toplak, M. E., i R. Tannock. "Tapping and Anticipation Performance in Attention Deficit Hyperactivity Disorder". Perceptual and Motor Skills 100, nr 3 (czerwiec 2005): 659–75. http://dx.doi.org/10.2466/pms.100.3.659-675.
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The objective of this study was to examine the precise timing of a motor response in a sample of adolescents with ADHD and comparison participants. 46 participants with ADHD ( M age = 15.6, SD = 1.4; 40 boys) and 44 control participants ( M age = 15.3, SD = 1.4; 40 boys) were recruited through a metropolitan hospital. Participants were administered a tapping task and an anticipation task. Adolescents with ADHD displayed significantly more intra-individual variability on the visual 1000-msec. frequency interval of the tapping task and displayed lower accuracy on the cued and uncued trials of the anticipation task than comparison participants. Intra-individual variability on the tapping task was correlated with intra-individual variability on the anticipation task within both the ADHD and control groups. These findings suggest that adolescents with ADHD have impairments in both the cognitive representation and motor production of the precise timing of a motor response.
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Rast, Philippe, i Daniel Zimprich. "Modeling Within-Person Variance in Reaction Time Data of Older Adults". GeroPsych 24, nr 4 (grudzień 2011): 169–76. http://dx.doi.org/10.1024/1662-9647/a000045.
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In order to model within-person (WP) variance in a reaction time task, we applied a mixed location scale model using 335 participants from the second wave of the Zurich Longitudinal Study on Cognitive Aging. The age of the respondents and the performance in another reaction time task were used to explain individual differences in the WP variance. To account for larger variances due to slower reaction times, we also used the average of the predicted individual reaction time (RT) as a predictor for the WP variability. Here, the WP variability was a function of the mean. At the same time, older participants were more variable and those with better performance in another RT task were more consistent in their responses.
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Lecerf, Thierry, Paolo Ghisletta i Céline Jouffray. "Intraindividual Variability and Level of Performance in Four Visuo-Spatial Working Memory Tasks". Swiss Journal of Psychology 63, nr 4 (grudzień 2004): 261–72. http://dx.doi.org/10.1024/1421-0185.63.4.261.
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Intraindividual variability and level of performance in accuracy of four visuo-spatial working memory tasks were examined in sixty-two young adults. The objective was to study the relationships between intraindividual variability and level of performance and to assess whether intraindividual variability is a useful marker of cognitive functioning. Correlational and factor analyses were performed. Confirmatory factor analyses rejected a two-factor representation, with a first factor representing level of performance and a second factor representing intraindividual variability. The best fitting model specified one factor per task and estimated significant within-task correlations of intraindividual variability residual scores. Overall, these findings are consistent with the view that performance variability provides valuable information independent of level of performance and different from noise.
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Samani, Afshin, Divya Srinivasan, Svend Erik Mathiassen i Pascal Madeleine. "Nonlinear metrics assessing motor variability in a standardized pipetting task: Between- and within-subject variance components". Journal of Electromyography and Kinesiology 25, nr 3 (czerwiec 2015): 557–64. http://dx.doi.org/10.1016/j.jelekin.2015.01.005.
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Vereijken, Beatrix. "The Complexity of Childhood Development: Variability in Perspective". Physical Therapy 90, nr 12 (1.12.2010): 1850–59. http://dx.doi.org/10.2522/ptj.20100019.
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The complexity of childhood development is exemplified in the variability of development that is seen across tasks and individuals. Furthermore, variability in performance is omnipresent within individuals across repetitions of a task and across individuals performing the same task. Previously, this variability was thought to reflect error of measurement or error of execution. On this account, variability reflects noise that should be filtered or averaged out of the data in order to reveal the “true” underlying characteristics of the performance. Although errors of measurement and execution indeed contribute to variability in movements, research in the last 2 decades has revealed characteristics of variability that are far more interesting than just noise. These characteristics can be deeply informative about underlying control processes and point to directions for clinical practice. This perspective article reviews different ways of characterizing variability, illustrates changes in variability as a result of development and learning, and discusses different theoretical perspectives on the role of variability that give clues about how to understand changes in variability and how to deal with variability in clinical settings.
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Wojtowicz, Magdalena, Erin L. Mazerolle, Virender Bhan i John D. Fisk. "Altered functional connectivity and performance variability in relapsing–remitting multiple sclerosis". Multiple Sclerosis Journal 20, nr 11 (11.03.2014): 1453–63. http://dx.doi.org/10.1177/1352458514524997.
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Background: Patients with multiple sclerosis (MS) demonstrate slower and more variable performance on attention and information processing speed tasks. Greater variability in cognitive task performance has been shown to be an important predictor of neurologic status and provides a unique measure of cognitive performance in MS patients. Objectives: This study investigated alterations in resting-state functional connectivity associated with within-person performance variability in MS patients. Methods: Relapsing–remitting MS patients and matched healthy controls completed structural MRI and resting-state fMRI (rsfMRI) scans, as well as tests of information processing speed. Performance variability was calculated from reaction time tests of processing speed. rsfMRI connectivity was investigated within regions associated with the default mode network (DMN). Relations between performance variability and functional connectivity in the DMN within MS patients were evaluated. Results: MS patients demonstrated greater reaction time performance variability compared to healthy controls ( p<0.05). For MS patients, more stable performance on a complex processing speed task was associated with greater resting-state connectivity between the ventral medial prefrontal cortex and the frontal pole. Conclusions: Among MS patients, greater functional connectivity between medial prefrontal and frontal pole regions appears to facilitate performance stability on complex speed-dependent information processing tasks.
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Higgins, Maureen B., Ronald Netsell i Laura Schulte. "Aerodynamic and Electroglottographic Measures of Normal Voice Production". Journal of Speech, Language, and Hearing Research 37, nr 1 (luty 1994): 38–45. http://dx.doi.org/10.1044/jshr.3701.38.
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The purpose of this investigation was to quantify the normal intrasubject performance variability of four measures of phonatory function within and across sessions. Two different speaking tasks, syllable series and sentence production, were used to determine if more natural speaking tasks resulted in greater intrasubject variability. Vowel type ([i] versus [a]) also was varied. Estimated subglottal air pressure, mean phonatory air flow, abduction quotient, and fundamental frequency were derived from aerodynamic and electroglottographic signals obtained from 11 normally speaking men and 10 normally speaking women on four different days. Relative intrasubject variability was compared across speaking task, gender, and vowel type. Average across-session intrasubject variability was 5% for fundamental frequency and abduction quotient, 8% for estimated subglottal air pressure, and 15% for mean phonatory air flow during syllable repetition. There was significantly greater intrasubject variability for mean phonatory air flow and abduction quotient for the sentence repetition task. There were no significant differences in intrasubject variability across gender and vowel type. The data were used to compute cutoff values that represent the amount of variability that would be considered within normal limits. These normal data can be used for comparison when assessing and monitoring the phonatory abilities of individuals with voice disorders.
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Franz, E. A., R. B. Ivry i L. L. Helmuth. "Reduced Timing Variability in Patients with Unilateral Cerebellar Lesions during Bimanual Movements". Journal of Cognitive Neuroscience 8, nr 2 (kwiecień 1996): 107–18. http://dx.doi.org/10.1162/jocn.1996.8.2.107.
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Timing variability on a repetitive tapping task was studied in subjects with unilateral cerebellar lesions. During unimanual tapping, within-hand variability was larger when tapping with the ipsilesional hand in comparison to tapping with the contralesional hand. However, variability in the impaired hand was greatly reduced when subjects tapped with two hands together. The improvement in within-hand variability during bimanual tapping was associated with a reduction in central variability rather than response implementation variability according to the two-process model of Wing and Kristofferson (1973). It is proposed that (1) each half of the cerebellum independently regulates the temporal aspects of movements on the ipsilateral side and (2) temporal coupling constraints require these separate signals to be integrated prior to response implementation for bimanual movements.
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Parma, Valentina, i Ashley B. de Marchena. "Motor signatures in autism spectrum disorder: the importance of variability". Journal of Neurophysiology 115, nr 3 (1.03.2016): 1081–84. http://dx.doi.org/10.1152/jn.00647.2015.
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In a recent study, Wang et al. ( J Neurophysiol 113: 1989–2001, 2015) used a precision grip force control task to unveil the contribution of feedforward and feedback mechanisms to sensorimotor dysfunction in autism spectrum disorder (ASD). Impairment of both motor control mechanisms was observed, along with significant variability in the motor response. In this Neuro Forum article we discuss these findings within the conceptual framework of the grasping circuit and within the broader context of clinical and research applications based on motor behavior.
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Vieluf, Solveig, Rita Sleimen-Malkoun, Claudia Voelcker-Rehage, Viktor Jirsa, Eva-Maria Reuter, Ben Godde, Jean-Jacques Temprado i Raoul Huys. "Dynamical signatures of isometric force control as a function of age, expertise, and task constraints". Journal of Neurophysiology 118, nr 1 (1.07.2017): 176–86. http://dx.doi.org/10.1152/jn.00691.2016.
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From the conceptual and methodological framework of the dynamical systems approach, force control results from complex interactions of various subsystems yielding observable behavioral fluctuations, which comprise both deterministic (predictable) and stochastic (noise-like) dynamical components. Here, we investigated these components contributing to the observed variability in force control in groups of participants differing in age and expertise level. To this aim, young (18–25 yr) as well as late middle-aged (55−65 yr) novices and experts (precision mechanics) performed a force maintenance and a force modulation task. Results showed that whereas the amplitude of force variability did not differ across groups in the maintenance tasks, in the modulation task it was higher for late middle-aged novices than for experts and higher for both these groups than for young participants. Within both tasks and for all groups, stochastic fluctuations were lowest where the deterministic influence was smallest. However, although all groups showed similar dynamics underlying force control in the maintenance task, a group effect was found for deterministic and stochastic fluctuations in the modulation task. The latter findings imply that both components were involved in the observed group differences in the variability of force fluctuations in the modulation task. These findings suggest that between groups the general characteristics of the dynamics do not differ in either task and that force control is more affected by age than by expertise. However, expertise seems to counteract some of the age effects. NEW & NOTEWORTHY Stochastic and deterministic dynamical components contribute to force production. Dynamical signatures differ between force maintenance and cyclic force modulation tasks but hardly between age and expertise groups. Differences in both stochastic and deterministic components are associated with group differences in behavioral variability, and observed behavioral variability is more strongly task dependent than person dependent.
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Stark-Inbar, Alit, Meher Raza, Jordan A. Taylor i Richard B. Ivry. "Individual differences in implicit motor learning: task specificity in sensorimotor adaptation and sequence learning". Journal of Neurophysiology 117, nr 1 (1.01.2017): 412–28. http://dx.doi.org/10.1152/jn.01141.2015.
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In standard taxonomies, motor skills are typically treated as representative of implicit or procedural memory. We examined two emblematic tasks of implicit motor learning, sensorimotor adaptation and sequence learning, asking whether individual differences in learning are correlated between these tasks, as well as how individual differences within each task are related to different performance variables. As a prerequisite, it was essential to establish the reliability of learning measures for each task. Participants were tested twice on a visuomotor adaptation task and on a sequence learning task, either the serial reaction time task or the alternating reaction time task. Learning was evident in all tasks at the group level and reliable at the individual level in visuomotor adaptation and the alternating reaction time task but not in the serial reaction time task. Performance variability was predictive of learning in both domains, yet the relationship was in the opposite direction for adaptation and sequence learning. For the former, faster learning was associated with lower variability, consistent with models of sensorimotor adaptation in which learning rates are sensitive to noise. For the latter, greater learning was associated with higher variability and slower reaction times, factors that may facilitate the spread of activation required to form predictive, sequential associations. Interestingly, learning measures of the different tasks were not correlated. Together, these results oppose a shared process for implicit learning in sensorimotor adaptation and sequence learning and provide insight into the factors that account for individual differences in learning within each task domain.NEW & NOTEWORTHY We investigated individual differences in the ability to implicitly learn motor skills. As a prerequisite, we assessed whether individual differences were reliable across test sessions. We found that two commonly used tasks of implicit learning, visuomotor adaptation and the alternating serial reaction time task, exhibited good test-retest reliability in measures of learning and performance. However, the learning measures did not correlate between the two tasks, arguing against a shared process for implicit motor learning.
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Nardolillo, Angel M., Amir Baghdadi i Lora A. Cavuoto. "Heart Rate Variability During a Simulated Assembly Task; Influence of Age and Gender". Proceedings of the Human Factors and Ergonomics Society Annual Meeting 61, nr 1 (wrzesień 2017): 1853–57. http://dx.doi.org/10.1177/1541931213601943.
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Attention has been concentrated on productivity in manufacturing settings with assembly line tasks being a common area of focus. Prolonged fatigue can occur during various assembly tasks both cognitively and physically. This can place a damper on efficiency and productivity for workers in manufacturing. Intercession can subsequently take place centered on reducing excessive workload tasks to assure a worker’s mental and physical thresholds are not contravened. Fatigue can be better understood by a person’s physiologic measures specifically their heart rate. Heart rate variability (HRV) which consists of calculations taken from each heartbeat can objectively quantify human capacity levels and the onset of fatigue. This study considers HRV during an assembly line task and compares differences in cardiac parameters between younger and older participants. The results obtained from this study were used to better understand the pattern of fatigue during the task at each segmented time interval. The HRV outcomes exhibited an index for each interval which gave the ability to make improved task demand decisions within the assembly line task. Statistical differences between age groups were also prominent which gave notion that workplace tasks should consider age classification when designing work structures for employees. This study assessed the potential function of HRV during a simulated task by examining the autonomic responses of the heart. The relationship between the autonomic nervous system to HRV was examined.
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Sibley, Ciara, Cyrus K. Foroughi, Noelle L. Brown, Henry Phillips, Sabrina Drollinger, Michael Eagle i Joseph T. Coyne. "More than Means: Characterizing Individual Differences in Pupillary Dilations". Proceedings of the Human Factors and Ergonomics Society Annual Meeting 64, nr 1 (grudzień 2020): 57–61. http://dx.doi.org/10.1177/1071181320641017.
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This study sought to characterize individual differences in pupillary dilations during a simple cognitive task. Eighty-four Navy and Marine Corps student pilots performed a digit memory recall test while their pupillary data were recorded. Results showed that peak pupil sizes significantly increased with difficulty of the memory task, however variability in pupillary dilations was substantial, with only 51% of individuals’ data corresponding with the aggregate results and dilations varying between participants by as much as 1 millimeter. The analyses presented in this paper illustrate the large individual variability that exists in pupil data, between individuals and even within individuals on a trial by trial basis. This work serves as a benchmark for understanding variability in pupillary dilations and encourages follow on work to explore casual mechanisms of differences in pupil dilations across individuals, especially before using pupil data for applied purposes.
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Abbeduto, Leonard, Katherine Short-Meyerson, Glenis Benson i Joanna Dolish. "Signaling of Noncomprehension by Children and Adolescents With Mental Retardation". Journal of Speech, Language, and Hearing Research 40, nr 1 (luty 1997): 20–32. http://dx.doi.org/10.1044/jslhr.4001.20.
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Previous research has demonstrated considerable within-individual and within- group variability in the signaling of noncomprehension by persons with mental retardation. The first purpose of this study was to determine whether within- individual variability in such signaling was related to differences in the nature of the inadequate message and the identity of the speaker. The second purpose was to evaluate the relationship between within-group variability in noncomprehension signaling and measures of cognition, receptive and expressive language ability, speech intelligibility, and social cognition. Participants were school-age individuals with mild mental retardation and typically developing children matched to them on nonverbal MA. Noncomprehension signaling was examined in a direction-following task in which inadequate message type and speaker were manipulated. It was found that message type, but not speaker, influenced noncomprehension signaling, with no difference between the two groups. We also found that performance on a test of receptive language ability was the best predictor of noncomprehension signaling for persons with mental retardation.
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Bradley, Evan D. "A Comparison of Stimulus Variability in Lexical Tone and Melody Perception". Psychological Reports 121, nr 4 (5.10.2017): 600–614. http://dx.doi.org/10.1177/0033294117734832.
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Music and language share perceptual resources, and both map sound to invariant categories—invariant over and within speakers for language and over instruments and keys for music. The effects of stimulus variability on lexical tone and musical interval tasks among non-tone language speakers were compared using a matching (XAB) task under varying levels of stimulus variability. Listeners perceived Mandarin words better with single rather than multiple speakers and showed similar advantages in melodic interval perception for low (single instrument) versus high (multiple instruments) variability sets. Lexical tone and musical interval perception were affected similarly by increasing stimulus variability, on average. However, the magnitude of variability effects within subjects was not well correlated between the tasks, providing no evidence for shared category-mapping mechanism for the two domains. Instead, it suggests that crossover between tone and melody processing is driven by shared encoding of acoustic-phonetic features, and that differences in performance and learning by tone language speakers and musicians in the other domain represent progress along a phonetic–phonological–lexical continuum.
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Wagner, Anita E., Leanne Nagels, Paolo Toffanin, Jane M. Opie i Deniz Başkent. "Individual Variations in Effort: Assessing Pupillometry for the Hearing Impaired". Trends in Hearing 23 (styczeń 2019): 233121651984559. http://dx.doi.org/10.1177/2331216519845596.
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Assessing effort in speech comprehension for hearing-impaired (HI) listeners is important, as effortful processing of speech can limit their hearing rehabilitation. We examined the measure of pupil dilation in its capacity to accommodate the heterogeneity that is present within clinical populations by studying lexical access in users with sensorineural hearing loss, who perceive speech via cochlear implants (CIs). We compared the pupillary responses of 15 experienced CI users and 14 age-matched normal-hearing (NH) controls during auditory lexical decision. A growth curve analysis was applied to compare the responses between the groups. NH listeners showed a coherent pattern of pupil dilation that reflects the task demands of the experimental manipulation and a homogenous time course of dilation. CI listeners showed more variability in the morphology of pupil dilation curves, potentially reflecting variable sources of effort across individuals. In follow-up analyses, we examined how speech perception, a task that relies on multiple stages of perceptual analyses, poses multiple sources of increased effort for HI listeners, wherefore we might not be measuring the same source of effort for HI as for NH listeners. We argue that interindividual variability among HI listeners can be clinically meaningful in attesting not only the magnitude but also the locus of increased effort. The understanding of individual variations in effort requires experimental paradigms that (a) differentiate the task demands during speech comprehension, (b) capture pupil dilation in its time course per individual listeners, and (c) investigate the range of individual variability present within clinical and NH populations.
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Simpson, Sean L., Mohsen Bahrami i Paul J. Laurienti. "A mixed-modeling framework for analyzing multitask whole-brain network data". Network Neuroscience 3, nr 2 (styczeń 2019): 307–24. http://dx.doi.org/10.1162/netn_a_00065.
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The emerging area of brain network analysis considers the brain as a system, providing profound insight into links between system-level properties and health outcomes. Network science has facilitated these analyses and our understanding of how the brain is organized. While network science has catalyzed a paradigmatic shift in neuroscience, methods for statistically analyzing networks have lagged behind. To address this for cross-sectional network data, we developed a mixed-modeling framework that enables quantifying the relationship between phenotype and connectivity patterns, predicting connectivity structure based on phenotype, simulating networks to gain a better understanding of topological variability, and thresholding individual networks leveraging group information. Here we extend this comprehensive approach to enable studying system-level brain properties across multiple tasks. We focus on rest-to-task network changes, but this extension is equally applicable to the assessment of network changes for any repeated task paradigm. Our approach allows (a) assessing population network differences in changes between tasks, and how these changes relate to health outcomes; (b) assessing individual variability in network differences in changes between tasks, and how this variability relates to health outcomes; and (c) deriving more accurate and precise estimates of the relationships between phenotype and health outcomes within a given task.
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Onushko, Tanya, Harsimran S. Baweja i Evangelos A. Christou. "Practice improves motor control in older adults by increasing the motor unit modulation from 13 to 30 Hz". Journal of Neurophysiology 110, nr 10 (15.11.2013): 2393–401. http://dx.doi.org/10.1152/jn.00345.2013.
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Practice of a motor task decreases motor output variability in older adults and is associated with adaptations of discharge activity of single motor units. In this study we were interested in the practice-induced modulation of multiple motor units within 13–30 Hz because theoretically it enhances the timing of active motoneurons. Our purpose, therefore, was to determine the neural adaptation of multiple motor units and related improvements in movement control following practice. Nine healthy older adults (65–85 yr) performed 40 practice trials of a sinusoidal task (0.12 Hz) with their index finger (10° range of motion). Multi-motor unit activity was recorded intramuscularly from the first dorsal interosseus muscle. The mean spike rate (MSR), spike rate variability (CVISI), and frequency modulation (5–60 Hz) of the spike rate were calculated from the multi-motor unit activity and were correlated with movement accuracy and variability of index finger position. A decrease in movement trajectory variability was associated with an increase in MSR ( R2 = 0.58), a decrease in CVISI ( R2 = 0.58), and an increase in total power within a 13- to 30-Hz band ( R2 = 0.48). The increase in total power within a 13- to 30-Hz band was associated significantly ( P < 0.005) with an increase in MSR ( R2 = 0.75) and the decrease in CVISI ( R2 = 0.70). We demonstrate that practice-induced improvements in movement control are associated with changes in activity of multiple motor units. These findings suggest that practice-induced improvements in movement steadiness of older adults are associated with changes in the modulation of the motoneuron pool from 13 to 30 Hz.
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Yao, Christie, Jill B. Rich, Ian F. Tannock, Bostjan Seruga, Kattleya Tirona i Lori J. Bernstein. "Pretreatment Differences in Intraindividual Variability in Reaction Time between Women Diagnosed with Breast Cancer and Healthy Controls". Journal of the International Neuropsychological Society 22, nr 5 (10.03.2016): 530–39. http://dx.doi.org/10.1017/s1355617716000126.
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AbstractObjectives: Chemotherapy has adverse effects on cognitive performance in women treated for breast cancer, but less is known about the period before chemotherapy. Studies have focused on mean level of performance, yet there is increasing recognition that variability in performance within an individual is also an important behavioral indicator of cognitive functioning and underlying neural integrity. Methods: We examined intraindividual variability (IIV) before chemotherapy and surgery in women diagnosed with breast cancer (n=31), and a healthy control group matched on age and education (n=25). IIV was calculated across trials of a computerized Stroop task, including an examination of the slowest and fastest trials of reaction time (RT) responses. Results: The groups were equivalent on overall accuracy and speed, and participants in both groups were less accurate and slower on incongruent trials compared with congruent trials. However, women with breast cancer became more variable with increased task difficulty relative to healthy controls. Among the slowest RT responses, women with breast cancer were significantly more variable than healthy controls on incongruent trials. This suggests that a specific variability-producing process (e.g., attentional lapses) occurs in task conditions that require executive control (e.g., incongruent trials). Conclusions: Results are consistent with other evidence of executive dysfunction among women treated for breast cancer. These findings highlight the importance of pretreatment assessment and show that variability in performance provides information about cognition that measures of central tendency do not. (JINS, 2016, 23, 1–10)
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Hancock, P. A., M. A. Robinson, A. L. Chu, D. R. Hansen, M. Vercruyssen, E. Grose i A. D. Fisk. "The Effects of Practice on Tracking and Subjective Workload". Proceedings of the Human Factors Society Annual Meeting 33, nr 19 (październik 1989): 1310–14. http://dx.doi.org/10.1177/154193128903301916.
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Six college-age male subjects performed one hundred, two-minute trials on a second-order tracking task. After each trial, subjects estimated perceived workload using both the NASA TLX and SWAT workload assessment procedures. Results confirmed an expected performance improvement on the tracking task which followed traditional learning curves within the performance of each individual. Perceived workload also decreased for both scales across trials. While performance variability significantly decreased across trials, workload variability remained constant. One month later, the same subjects returned to complete the second experiment in the sequence which was a retention replication of the first experiment. Results replicated those for the first experiment except that both performance error and workload were at reduced overall levels. Results in general affirm a parallel workload reduction with performance improvement, an observation consistent with a resource-based view of automaticity.
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Matuz, András, Dimitri van der Linden, Zsolt Kisander, István Hernádi, Karádi Kázmér i Árpád Csathó. "Enhanced cardiac vagal tone in mental fatigue: Analysis of heart rate variability in Time-on-Task, recovery, and reactivity". PLOS ONE 16, nr 3 (3.03.2021): e0238670. http://dx.doi.org/10.1371/journal.pone.0238670.
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Heart Rate Variability (HRV) has been suggested as a useful tool to assess fatigue-sensitive psychological operations. The present study uses a between and within-subject design with a cognitively demanding task and a documentary viewing condition, to examine the temporal profile of HRV during reactivity, Time-on-Task (ToT), and recovery. In the cognitive task group, participants worked on a bimodal 2-back task with a game-like character (the Gatekeeper task) for about 1.5 hours, followed by a 12-minute break, and a post-break block of performance (about 18 min). In the other group, participants watched documentaries. We hypothesized an increasing vagal-mediated HRV as a function of Time spent on the Gatekeeper task and no HRV change in the documentary viewing group. We also analyzed the trial-based post-response cardiac activity as a physiological associate of task-related motivation. Relative to the documentary-viewing, ToT was associated with an elevated level of subjective fatigue, decreased heart rate, and increased HRV, particularly in the vagal-mediated components. Based on fatigued participants’ post-error cardiac slowing, and post-error reaction time analyses, we found no evidence for motivation deficits. The present findings suggest that the parasympathetic branch of the autonomous nervous system functioning as a relaxation system tends to be activated under increasing mental fatigue. In addition, the study shows that many HRV indices also seem to change when individuals are engaged in a prolonged, less fatiguing activity (e.g. documentary viewing). This finding emphasizes the relevance of comparisons/control conditions in ToT experiments.
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Sandercock, Gavin. "Normative values, reliability and sample size estimates in heart rate variability". Clinical Science 113, nr 3 (2.07.2007): 129–30. http://dx.doi.org/10.1042/cs20070137.
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HRV (heart rate variability) is a non-invasive maker of cardiac autonomic modulation utilized in many hundreds of scientific studies each year. The reliability of heart rate variability has been frequently investigated yet remains poorly quantified. Assessing the reliability of a measure that assesses dynamic physiological processes and shows large between- and within-subject variation is a complex task. In this issue of Clinical Science, Pinna and co-workers provide excellent insight into the test–retest reliability of commonly used HRV indices and put the values obtained into context by comparing them with levels of between-subject variation and by producing sample size estimates.
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Posada-Quintero, Hugo F., i Jeffrey B. Bolkhovsky. "Machine Learning models for the Identification of Cognitive Tasks using Autonomic Reactions from Heart Rate Variability and Electrodermal Activity". Behavioral Sciences 9, nr 4 (25.04.2019): 45. http://dx.doi.org/10.3390/bs9040045.
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Indices of heart rate variability (HRV) and electrodermal activity (EDA), in conjunction with machine learning models, were used to identify one of three tasks a subject is performing based on autonomic response elicited by the specific task. Using non-invasive measures to identify the task performed by a subject can help to provide individual monitoring and guidance to avoid the consequences of reduced performance due to fatigue or other stressors. In the present study, sixteen subjects were enrolled to undergo three tasks: The psychomotor vigilance task (PVT), an auditory working memory task (the n-back paradigm), and a visual search (ship search, SS). Electrocardiogram (ECG) (for HRV analysis) and EDA data were collected during the tests. For task-classification, we tested four machine learning classification tools: k-nearest neighbor classifier (KNN), support vector machines (SVM), decision trees, and discriminant analysis (DA). Leave-one-subject-out cross-validation was used to evaluate the performance of the constructed models to prevent overfitting. The most accurate models were the KNN (66%), linear SVM (62%), and linear DA (62%). The results of this study showed that it is possible to identify the task a subject is performing based on the subject’s autonomic reactions (from HRV and EDA). This information can be used to monitor individuals within a larger group to assist in reducing errors caused by uncoordinated or poor performance by allowing for automated tracking of and communication between individuals.
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ELSINGER, CATHERINE L., STEPHEN M. RAO, JANICE L. ZIMBELMAN, NORMAN C. REYNOLDS, KAREN A. BLINDAUER i RAYMOND G. HOFFMANN. "Neural basis for impaired time reproduction in Parkinson's disease: An fMRI study". Journal of the International Neuropsychological Society 9, nr 7 (listopad 2003): 1088–98. http://dx.doi.org/10.1017/s1355617703970123.
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Studies involving brain-lesioned subjects have used the paced finger tapping (PFT) task to investigate the neural systems that govern motor timing. Patients with Parkinson's disease (PD), for example, demonstrate abnormal performance on the PFT, characterized by decreased accuracy and variability changes, suggesting that the basal ganglia may play a critical role in motor timing. Consistent with this hypothesis, an fMRI study of healthy participants demonstrated that the medial frontostriatal circuit (dorsal putamen, ventrolateral thalamus, SMA) correlated with explicit time-dependent components of the PFT task. In the current fMRI study, PD patients and healthy age-matched controls were imaged while performing the PFT. PD patients underwent 2 imaging sessions, 1 on and the other off dopamine supplementation. Relative to controls, PD patients were less accurate and showed greater variability on the PFT task relative to controls. No PFT performance differences were observed between the on and off medication states despite significantly greater motor symptoms on the Unified Parkinson's Disease Rating Scale (UPDRS) in the off medication state. Functional imaging results demonstrated decreased activation within the sensorimotor cortex (SMC), cerebellum, and medial premotor system in the PD patients compared to controls. With dopamine replacement, an increase in the spatial extent of activation was observed within the SMC, SMA, and putamen in the PD patients. These results indicate that impaired timing reproduction in PD patients is associated with reduced brain activation within motor and medial premotor circuits. Despite a lack of improvement in PFT performance, PD patient's brain activation patterns were partially “normalized” with dopamine supplementation. These findings could not be attributed to greater head movement artifacts or basal ganglia atrophy within the PD group. (JINS, 2003, 9, 1088–1098.)
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Spunt, Robert P., Matthew D. Lieberman, Jessica R. Cohen i Naomi I. Eisenberger. "The Phenomenology of Error Processing: The Dorsal ACC Response to Stop-signal Errors Tracks Reports of Negative Affect". Journal of Cognitive Neuroscience 24, nr 8 (sierpień 2012): 1753–65. http://dx.doi.org/10.1162/jocn_a_00242.
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A reliable observation in neuroimaging studies of cognitive control is the response of dorsal ACC (dACC) to events that demand increased cognitive control (e.g., response conflicts and performance errors). This observation is apparently at odds with a comparably reliable association of the dACC with the subjective experience of negative affective states such as pain, fear, and anxiety. Whereas “affective” associates of the dACC are based on studies that explicitly manipulate and/or measure the subjective experience of negative affect, the “cognitive” associates of dACC are based on studies using tasks designed to manipulate the demand for cognitive control, such as the Stroop, flanker, and stop-signal tasks. Critically, extant neuroimaging research has not systematically considered the extent to which these cognitive tasks induce negative affective experiences and, if so, to what extent negative affect can account for any variance in the dACC response during task performance. While undergoing fMRI, participants in this study performed a stop-signal task while regularly reporting their experience of performance on several dimensions. We observed that within-subject variability in the dACC response to stop-signal errors tracked changes in subjective frustration throughout task performance. This association remained when controlling for within-subject variability in subjective reports of cognitive engagement and several performance-related variables indexing task difficulty. These results fit with existing models characterizing the dACC as a hub for monitoring ongoing behavior and motivating adjustments when necessary and further emphasize that such a function may be linked to the subjective experience of negative affect.
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Poon, Cynthia, Stephen A. Coombes, Daniel M. Corcos, Evangelos A. Christou i David E. Vaillancourt. "Transient shifts in frontal and parietal circuits scale with enhanced visual feedback and changes in force variability and error". Journal of Neurophysiology 109, nr 8 (15.04.2013): 2205–15. http://dx.doi.org/10.1152/jn.00969.2012.
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When subjects perform a learned motor task with increased visual gain, error and variability are reduced. Neuroimaging studies have identified a corresponding increase in activity in parietal cortex, premotor cortex, primary motor cortex, and extrastriate visual cortex. Much less is understood about the neural processes that underlie the immediate transition from low to high visual gain within a trial. This study used 128-channel electroencephalography to measure cortical activity during a visually guided precision grip task, in which the gain of the visual display was changed during the task. Force variability during the transition from low to high visual gain was characterized by an inverted U-shape, whereas force error decreased from low to high gain. Source analysis identified cortical activity in the same structures previously identified using functional magnetic resonance imaging. Source analysis also identified a time-varying shift in the strongest source activity. Superior regions of the motor and parietal cortex had stronger source activity from 300 to 600 ms after the transition, whereas inferior regions of the extrastriate visual cortex had stronger source activity from 500 to 700 ms after the transition. Force variability and electrical activity were linearly related, with a positive relation in the parietal cortex and a negative relation in the frontal cortex. Force error was nonlinearly related to electrical activity in the parietal cortex and frontal cortex by a quadratic function. This is the first evidence that force variability and force error are systematically related to a time-varying shift in cortical activity in frontal and parietal cortex in response to enhanced visual gain.
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Martins, João Bernardo, Isabel Mesquita, Ademilson Mendes, Letícia Santos i José Afonso. "Inter-player variability in game patterns in high-level women's volleyball: A study with Outside Hitters (Near vs. Away) using Social Network Analysis. [Variabilidad entre jugadores en los patrones de juego en el voleibol femenino de alto nivel: Un estudio con bateadores externos (Cerca versus Lejos) usando Análisis de Redes Sociales]." RICYDE. Revista internacional de ciencias del deporte 17, nr 65 (1.07.2021): 234–50. http://dx.doi.org/10.5232/ricyde2021.06503.
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A wide body of research on team sports has focused on positional status based differences, providing information on inter-player variability according to the functional roles within the game. However, research addressing inter-player variability within the same positional/function status is scarce. The present article presents an analysis of inter-player variability within the same positional status during critical moments, in high-level women's volleyball, using Social Network Analysis. Attack actions of the outside hitters near (OHN) and away (OHA) from the setter were analysed in ten matches from the 2019 Volleyball Nations League Finals (268 plays). Two independent Eigenvector Centrality networks were created, one for OHN and another for OHA. Main results: (a) in side-out with ideal setting conditions, the OHA used more tips and exploration of the block than the OHN; under non-ideal setting conditions, the OHN had slower attack tempos than the OHA; (b) OHA used tip and directed attacks after error situations while OHN was typically not requested after error situations; (c) in transition, OHN typically attacked after having performed a previous action, performing a dual task within each ball possession, while OHA only attacked when there was no prior action; (d) there were also inter-positional similarities, with both OHN and OHA preferring a strong attack in ideal conditions during KI and KIV, and slower tempos in transition in non-ideal conditions. Conclusions: Even within the same positional status, there seems to be subtle, but relevant inter-player variability. Consequently, coaches should devote careful attention when assigning players to positional.
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Adams, Catherine M., i David W. Biers. "Effect of Pairted Comparison Weighting and Weighting Context". Proceedings of the Human Factors and Ergonomics Society Annual Meeting 44, nr 37 (lipiec 2000): 610–13. http://dx.doi.org/10.1177/154193120004403717.
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The present study compared three subjective workload measurement techniques—a unidimensional scale (UW) and two mutidimenional scales (TLX and ModSWAT)–using a continuous memory task. ModSWAT is a technique that uses the sum of the SWAT dimensions to form the workload composite rather than the standard conjoint measurement procedure. Both weighted and unweighted workload measures were obtained for the two multidimensional scales. The paired-comparison technique used by TLX was employed to weight the three SWAT dimensions. For both multidimensional scales, weighting context was also varied. Paired comparison of the workload dimensions was made either prior to the task in a general context or within context of the task just performed. The major findings were that: (1) ModSWAT and UW were more sensitive than TLX to the task demands (i.e., difficulty) of the continuous recognition task; (2) weighting context affected the weights that were assigned the workload dimensions for both TLX and ModSWAT; (3) weighting context did not affect the weighted workload scores; and (4) the weighted and unweighted workload composites were very similar. Results were interpreted within context of averaging across multiple dimensions when several dimensions are insensitive to the task demands. Variability in the weights assigned contributed to the failure to find a effect of weighting.
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Jungclaus, J. H., S. J. Lorenz, C. Timmreck, C. H. Reick, V. Brovkin, K. Six, J. Segschneider i in. "Climate and carbon-cycle variability over the last millennium". Climate of the Past Discussions 6, nr 3 (26.05.2010): 1009–44. http://dx.doi.org/10.5194/cpd-6-1009-2010.
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Abstract. A long-standing task in climate research has been to distinguish between anthropogenic climate change and natural climate variability. A prerequisite for fulfilling this task is the understanding of the relative roles of external drivers and internal variability of climate and the carbon cycle. Here, we present the first ensemble simulations over the last 1200 years with a comprehensive Earth system model including a fully interactive carbon cycle. Applying up-to-date reconstructions of external forcing including the recent low-amplitude estimates of solar variations, the ensemble simulations reproduce temperature evolutions consistent with the range of reconstructions. The 20th-century warming trend stands out against all pre-industrial trends within the ensemble. Volcanic eruptions are necessary to explain variations in pre-industrial climate such as the Little Ice Age; yet only the strongest, repeated eruptions lead to cooling trends that stand out against the internal variability across all ensemble members. The simulated atmospheric CO2 concentrations exhibit a stable carbon cycle over the pre-industrial era with multi-centennial variations somewhat smaller than in the observational records. Early land-cover changes have modulated atmospheric CO2 concentrations only slightly. We provide a model-based quantification of the sensitivity (termed γ) of the global carbon cycle to temperature for a variety of climate and forcing conditions. The magnitude of γ agrees with a recent statistical assessment based on reconstruction data. We diagnose a distinct dependence of γ on the forcing strength and time-scales involved, thus providing an explanation for the systematic difference in the observational estimates for different segments of the last millennium.
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Jungclaus, J. H., S. J. Lorenz, C. Timmreck, C. H. Reick, V. Brovkin, K. Six, J. Segschneider i in. "Climate and carbon-cycle variability over the last millennium". Climate of the Past 6, nr 5 (26.10.2010): 723–37. http://dx.doi.org/10.5194/cp-6-723-2010.
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Abstract. A long-standing task in climate research has been to distinguish between anthropogenic climate change and natural climate variability. A prerequisite for fulfilling this task is the understanding of the relative roles of external drivers and internal variability of climate and the carbon cycle. Here, we present the first ensemble simulations over the last 1200 years with a comprehensive Earth system model including a fully interactive carbon cycle. Applying up-to-date reconstructions of external forcing including the recent low-amplitude estimates of solar variations, the ensemble simulations reproduce temperature evolutions consistent with the range of reconstructions. The 20th-century warming trend stands out against all pre-industrial trends within the ensemble. Volcanic eruptions are necessary to explain variations in pre-industrial climate such as the Little Ice Age; yet only the strongest, repeated eruptions lead to cooling trends that differ significantly from the internal variability across all ensemble members. The simulated atmospheric CO2 concentrations exhibit a stable carbon cycle over the pre-industrial era with multi-centennial variations somewhat smaller than in the observational records. Early land-cover changes have modulated atmospheric CO2 concentrations only slightly. We provide a model-based quantification of the sensitivity (termed γ) of the global carbon cycle to temperature for a variety of climate and forcing conditions. We diagnose a distinct dependence of γ on the forcing strength and time-scales involved, thus providing a possible explanation for the systematic difference in the observational estimates for different segments of the last millennium.
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Santos-Pinto, Luís, i Joel Sobel. "A Model of Positive Self-Image in Subjective Assessments". American Economic Review 95, nr 5 (1.11.2005): 1386–402. http://dx.doi.org/10.1257/000282805775014245.
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This paper suggests a mechanism that describes individuals' positive self-image in subjective assessments of their relative abilities. The mechanism assumes individuals have heterogeneous production functions that determine ability as a function of multiple skills; make skill-enhancing investments with the goal of maximizing their ability; and make ability comparisons using their own production function. Within this framework, the paper provides conditions under which there is positive self-image. Positive self-image is increasing in the ease of the task, the number of different skills needed for the task, and the variability of production technologies in the population.
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Jarvis, Danielle N., Jo Armour Smith i Kornelia Kulig. "Trunk Coordination in Dancers and Nondancers". Journal of Applied Biomechanics 30, nr 4 (sierpień 2014): 547–54. http://dx.doi.org/10.1123/jab.2013-0329.
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Variability, or how a task changes across trials, may reveal differences between athletes of differing skill levels. The purpose of this study was to examine trunk and lower extremity (LE) single joint kinematic variability and intersegmental coordination variability in dancers and nondancers during bipedal vertical dance jumps (sautés). Twenty healthy females, 10 with no formal dance training and 10 professional dancers, performed 20 consecutive sautés. Single joint kinematic variability was assessed using mean standard deviation of angular displacement, and intersegmental coordination variability was assessed using angular deviation of the coupling angle between segments. Within the context of the standard error of measure, there was no difference in single joint kinematic variability between dancers and nondancers. Intersegmental coordination variability in the trunk was higher than variability in LE couplings for both groups. Dancers had lower intersegmental coordination variability than nondancers for LE sagittal, frontal, and transverse plane couplings, and sagittal plane trunk couplings. Trunk adjustments may be important for successful performance, but lower intersegmental coordination variability in expert dancers indicates a higher level of control. Trunk coordination and postural control may be important factors to investigate in skilled athletes.
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Herdener, Nathan, Benjamin A. Clegg, Christopher D. Wickens i C. A. P. Smith. "Can You See It? Perceived Variance in Scatterplot Visualization". Proceedings of the Human Factors and Ergonomics Society Annual Meeting 63, nr 1 (listopad 2019): 1714–18. http://dx.doi.org/10.1177/1071181319631094.
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Understanding uncertainty in spatial domains (such as hurricane forecasting) is both important and challenging, often leading to overconfidence and underestimation of variability. The underlying source of the difficulty is not well understood, as this complex domain requires perceptual, attentional, and memory related cognitive abilities. The present study explores the impact of perception on understanding of variability in an abstract spatial task. Individuals were shown a scatter chart type display of possible endpoints of an uncertain trajectory and asked to make two separate judgements of variability: adjusting a circle to encompass 75% of endpoints and estimating the likelihood the trajectory would fall within an experimenter defined probe circle. Calibration to changes in variability were calculated for each individual on both measures and compared against each other. Results indicate a lack of sensitivity in interpreting visualized spatial uncertainty among many individuals, with performance differing depending on the probe method employed. Implications are discussed.
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Etnyre, Bruce R., Eva J. Lee i Hally B. W. Poindexter. "Variability of Positioning Accuracy following a Maximum Isometric Contraction". Perceptual and Motor Skills 64, nr 3 (czerwiec 1987): 759–64. http://dx.doi.org/10.2466/pms.1987.64.3.759.
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The purpose of this study was to examine the effects of different contraction times and delay times prior to a positioning task. While blindfolded, each of 25 subjects learned to produce elbow-extension movements to a short and a long target using a kinesthesiometer. The subject then produced 30 trials without feedback to each target. These control trials were preceded by a foreperiod of 0-, 3-, or 6-sec. delay. The 60 experimental trials were identical to control trials except the subject isometrically contracted elbow extensor muscles for 3 or 6 sec. prior to each trial. Following each isometric contraction the subject delayed movement for 0, 3, or 6 sec. The 3-sec. and 6-sec. prepositioning contractions produced greater undershooting and variability than no prepositioning contractions, and the 0-sec. delay produced less constant error than either the 3- or 6-sec. delay. It was concluded that following isometric contraction, undershooting a target occurred and this effect did not dissipate within a 6-sec. period.
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Cox, Roy, Anna C. Schapiro i Robert Stickgold. "Variability and stability of large-scale cortical oscillation patterns". Network Neuroscience 2, nr 4 (październik 2018): 481–512. http://dx.doi.org/10.1162/netn_a_00046.
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Individual differences in brain organization exist at many spatiotemporal scales and underlie the diversity of human thought and behavior. Oscillatory neural activity is crucial for these processes, but how such rhythms are expressed across the cortex within and across individuals is poorly understood. We conducted a systematic characterization of brain-wide activity across frequency bands and oscillatory features during rest and task execution. We found that oscillatory profiles exhibit sizable group-level similarities, indicating the presence of common templates of oscillatory organization. Nonetheless, well-defined subject-specific network profiles were discernible beyond the structure shared across individuals. These individualized patterns were sufficiently stable to recognize individuals several months later. Moreover, network structure of rhythmic activity varied considerably across distinct oscillatory frequencies and features, indicating the existence of several parallel information processing streams embedded in distributed electrophysiological activity. These findings suggest that network similarity analyses may be useful for understanding the role of large-scale brain oscillations in physiology and behavior.
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Doran, Carolina, Martin C. Stumpe, Ana Sendova-Franks i Nigel R. Franks. "Exploration adjustment by ant colonies". Royal Society Open Science 3, nr 1 (styczeń 2016): 150533. http://dx.doi.org/10.1098/rsos.150533.
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How do animals in groups organize their work? Division of labour, i.e. the process by which individuals within a group choose which tasks to perform, has been extensively studied in social insects. Variability among individuals within a colony seems to underpin both the decision over which tasks to perform and the amount of effort to invest in a task. Studies have focused mainly on discrete tasks, i.e. tasks with a recognizable end. Here, we study the distribution of effort in nest seeking, in the absence of new nest sites. Hence, this task is open-ended and individuals have to decide when to stop searching, even though the task has not been completed. We show that collective search effort declines when colonies inhabit better homes, as a consequence of a reduction in the number of bouts (exploratory events). Furthermore, we show an increase in bout exploration time and a decrease in bout instantaneous speed for colonies inhabiting better homes. The effect of treatment on bout effort is very small; however, we suggest that the organization of work performed within nest searching is achieved both by a process of self-selection of the most hard-working ants and individual effort adjustment.
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Wikenheiser, Andrew M., i A. David Redish. "Changes in reward contingency modulate the trial-to-trial variability of hippocampal place cells". Journal of Neurophysiology 106, nr 2 (sierpień 2011): 589–98. http://dx.doi.org/10.1152/jn.00091.2011.
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Pyramidal cells in the rodent hippocampus often exhibit clear spatial tuning. Theories of hippocampal function suggest that these “place cells” implement multiple, independent neural representations of position (maps), based on different reference frames or environmental features. Consistent with the “multiple maps” theory, previous studies have shown that manipulating spatial factors related to task performance modulates the within-session variability (overdispersion) of cells in the hippocampus. However, the influence of changes in reward contingency on overdispersion has not been examined. To test this, we first trained rats to collect food from three feeders positioned around a circular track (task1). When subjects were proficient, the reward contingency was altered such that every other feeder delivered food (task2). We recorded ensembles of hippocampal neurons as rats performed both tasks. Place cell overdispersion was high during task1 but decreased significantly during task2, and this increased reliability could not be accounted for by changes in running speed or familiarity with the task. Intuitively, decreased variability might be expected to improve neural representations of position. To test this, we used Bayesian decoding of hippocampal spike trains to estimate subjects' location. Neither the amount of probability decoded to subjects' position (local probability) nor the difference between estimated position and true location (decoding accuracy) differed between tasks. However, we found that hippocampal ensembles were significantly more self-consistent during task2 performance. These results suggest that changes in task demands can affect the firing statistics of hippocampal neurons, leading to changes in the properties of decoded neural representations.
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Edison, Bianca, Bridget O’Callahan, Nicole M. Mueske, Adriana Conrad-Forrest, Mia J. Katzel, Tracy Zaslow i Tishya A. L. Wren. "MOVEMENT VARIABILITY IN PRE-TEEN AND TEENAGE ATHLETES DURING SPORTS RELATED TASKS". Orthopaedic Journal of Sports Medicine 8, nr 4_suppl3 (1.04.2020): 2325967120S0015. http://dx.doi.org/10.1177/2325967120s00151.
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Background: Movement variability may affect injury assessment and may change as athletes mature. Hypothesis/Purpose: We hypothesized that pre-teen athletes would exhibit greater variability than teenage athletes when performing drop jump, heel touch, and single leg hop motions. Methods: 55 uninjured pediatric athletes were divided into pre-teen (age 7-12 years; n=29; 11 female) and teenage (age 13-15 years; n=26; 13 female) groups of similar size. All participants performed 2-3 repetitions per side of three sports related tasks: drop jump (41 cm), heel touch (single-leg squat from 15 cm or 23 cm step, depending on whether subject height <155 cm), and single leg hop for distance. 3D kinematics were recorded using motion capture during the loading phase of each task. To assess intra-individual variability, we examined the standard deviation (SD) and range (maximum-minimum) of key metrics among the multiple repetitions of each task performed by each participant. Variability was compared between age groups using 2-sided t-tests. Results: In the drop jump and heel touch, the younger group was more variable than the older group (Figure 1.1 left). The median within-subject SD of repeat measurements varied from 1-6° in the sagittal plane, 1-3° in the frontal plane, and 1-4° in the transverse plane over both groups (Table 1.2), while the within-subject range of measurements varied from 2-11° in the sagittal, 2-5° in the frontal, and 2-7° in the transverse planes (Table 1.3). Representing a worst-case scenario, the 95th percentile for range of measurements was >15° for many sagittal plane variables and >10° for many frontal and transverse plane variables in the younger group. In the singl- leg hop, the older group was much more variable than the younger group in the sagittal plane, particularly at the trunk, pelvis, and ankle (Figure 1.1 right). The younger group was still more variable than the older group at the trunk and pelvis in the transverse plane. Median within-subject variability ranged from 2-9° for SD and 3-17° for range of repeat measurements. Conclusion: There was substantial within-subject variability in performing sports related tasks for pediatric athletes of all ages. Variability was generally lower for older athletes, but was particularly high in the older group for sagittal plane trunk and pelvis motion during single-leg hop landing, which may reflect the need to adjust for less constrained positioning of a larger proximal mass. The high variability in performing sports tasks suggests that multiple trials should be analyzed for a more complete and representative evaluation. [Figure: see text][Table: see text][Table: see text]
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Poole, Daniel, Daniel Poole, Samuel Couth, Daniel Poole, Samuel Couth, Emma Gowen, Daniel Poole i in. "Adapting the Crossmodal Congruency Task for Measuring the Limits of Visual–Tactile Interactions Within and Between Groups". Multisensory Research 28, nr 3-4 (2015): 227–44. http://dx.doi.org/10.1163/22134808-00002475.
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The crossmodal congruency task (CCT) is a commonly used paradigm for measuring visual–tactile interactions and how these may be influenced by discrepancies in space and time between the tactile target and visual distractors. The majority of studies which have used this paradigm have neither measured, nor attempted to control, individual variability in unisensory (tactile) performance. We have developed a version of the CCT in which unisensory baseline performance is constrained to enable comparisons within and between participant groups. Participants were instructed to discriminate between single and double tactile pulses presented to their dominant hand, at their own approximate threshold level. In Experiment 1, visual distractors were presented at −30 ms, 100 ms, 200 ms and 400 ms stimulus onset asynchronies. In Experiment 2, ipsilateral visual distractors were presented 0 cm, 21 cm, and 42 cm vertically from the target hand, and 42 cm in a symmetrical, contralateral position. Distractors presented −30 ms and 0 cm from the target produced a significantly larger congruency effect than at other time points and spatial locations. Thus, the typical limits of visual–tactile interactions were replicated using a version of the task in which baseline performance can be constrained. The usefulness of this approach is supported by the observation that tactile thresholds correlated with self-reported autistic traits in this non-clinical sample. We discuss the suitability of this adapted version of the CCT for measuring visual–tactile interactions in populations where unisensory tactile ability may differ within and between groups.