Synergies and Motor Equivalence in Voluntary Sway Tasks: The Effects of Visual and Mechanical Constraints

The authors used two analyses developed within the framework of the uncontrolled manifold hypothesis to quantify multimuscle synergies during voluntary body sway: analysis of intertrial variance and analysis of motor equivalence with respect to the center of pressure (COP) trajectory. Participants performed voluntary sway tasks in the anteroposterior direction at 0.33 and 0.66 Hz. Muscle groups were identified in the space of muscle activations and used as elemental variables in the synergy analyses. Changing mechanical and vision feedback–based constraints led to significant changes in indices of sway performance such as COP deviations in the uninstructed, mediolateral direction and indices of spontaneous postural sway. In contrast, there were no significant effects on synergy indices. These findings show that the neural control of performance and of its stability may involve different control variables and neurophysiological structures. There were strong correlations between the indices of motor equivalence and those computed using the intercycle variance analysis. This result is potentially important for studies of patients with movement disorders who may be unable to perform multiple trials (cycles) at any given task, making analysis of motor equivalence of single trials a viable alternative to explore changes in stability of actions.     

Exploring and integrating discrete and dimensional approaches while inducing negative emotional states

Selecting visual stimuli for inducing specific emotional states is very challenging, since the choice relies on specific conceptualization of emotions. In this work, we present a set of 55 stimuli, realized integrating discrete and dimensional theories of emotions, and specifically selected to investigate anger, fear, and disgust reactions in non-clinical and clinical contexts. Our set of stimuli presents several aspects of novelty since (1) a large and heterogeneous sample of subjects from the general population was involved in the labelling task, and (2) bivariate and multivariate statistical techniques were applied to integrate emotion models. The proposed set of stimuli could be useful for researchers and other professionals in the affective sciences to address negative emotion recognition issues within a broader perspective both in general population and in psychiatric samples. The obtained comprehensive characterization of the stimuli allowed us to confirm the sexual dimorphism in emotional processing.     

Effects of information accuracy and volume on decision making

Recent advances in information technology have resulted in increasingly complex work environments. Much of the complexity is due to a deluge of information available across networks (Gleick, 2011) and unknown reliability, which introduces additional uncertainty (Platt & Huettel, 2008). Understanding the performance characteristics of human information processing for optimal decision making under such conditions of data abundance and uncertainty is critical in complex networked information environments, such as military operations. One focus of the United States military is providing troops with the richness of information formally reserved for higher echelons (Bawden & Robinson, 2009). However, this effort risks cognitive overload, where too much information can result in impaired performance. The present study examined human decision making under varying levels of cognitive load and source reliability. Participants determined the reliability of two information sources and decided how to use them to minimize cognitive load and improve performance in a visual search task. Unbeknownst to participants, one source provided highly accurate information and one provided moderately accurate information. Results showed that participants had more trust in the more accurate than the less accurate source, and decision making accuracy decreased as cognitive load increased. When cognitive load was highest, participants were more accurate on trials with the more accurate source. Thus, the more accurate source facilitated better performance, whether through better intel or through participants offloading some of the cognitive load to the reliable source.     

精神运动警觉性任务在不同知觉负荷下的疲劳状态监测

精神疲劳是由于长时间的认知活动引起的一种疲劳形式,不同任务水平可能造成不同的疲劳状态。本研究采用双任务范式,利用精神运动警觉性任务(Psychomotor Vigilance Task,PVT)的不同指标,考察了不同任务水平下的视觉搜索任务引起的不同精神疲劳状态。结果发现:PVT任务的最快10%反应时指标与自评疲劳程度结果一致,随着任务持续时间的增加而增加,最快10%反应时能够反映不同任务水平条件下的疲劳状态变化。注意忽视频次指标能够反映简单任务条件下的疲劳状态变化。平均反应时指标的时间主效应和任务主效应都显著,可能是反映精神疲劳状态和任务负荷情况的综合指标。PVT任务的最慢10%反应时指标,仅仅存在显著的任务效应,可能主要体现了任务负荷状态的变化。这些结果表明,PVT任务各指标能够反映不同任务水平引起的疲劳状态的不同变化,是研究和监测不同状态下精神疲劳程度较好的任务选择。     

Rightly Dividing the Word of Truth: Recent Reference Works in Religious Studies

ABSTRACT

Several useful multi-volume reference works have been published during the past 2 years. This review essay profiles several of these resources and introduces them to theological librarians and their patrons.     

Perceptual span,visual span,and visual attention span: Three potential ways to quantify limits on visual processing during reading

Many lines of evidence have revealed limitations of the human visual system, most notably that only a portion of available information is processed in a single glance. A degree of conceptual confusion has emerged, however, regarding the underlying concepts or mechanisms explaining limited visual processing in reading; perceptual span, visual span, or visual attention span. While the original definitions of these three concepts are clear and well-differentiated, they are routinely used inconsistently in the literature. The primary goal of the present review is to re-specify these three concepts in terms of what they correspond to and how they are determined. Further, we investigate whether these three spans refer to vision-related measurements and/or are based on general cognitive abilities. This review should lead to a better understanding of the involvement of visual functions in reading performance.     

You detect while I search: examining visual search efficiency in a joint search task

Numerous factors impact attentional allocation, with behaviour being strongly influenced by the interaction between individual intent and our visual environment. Traditionally, visual search efficiency has been studied under solo search conditions. Here, we propose a novel joint search paradigm where one individual controls the visual input available to another individual via a gaze contingent window (e.g., Participant 1 controls the window with their eye movements and Participant 2 – in an adjoining room – sees only stimuli that Participant 1 is fixating and responds to the target accordingly). Pairs of participants completed three blocks of a detection task that required them to: (1) search and detect the target individually, (2) search the display while their partner performed the detection task, or (3) detect while their partner searched. Search was most accurate when the person detecting was doing so for the second time while the person controlling the visual input was doing so for the first time, even when compared to participants with advanced solo or joint task experience (Experiments 2 and 3). Through surrendering control of one’s search strategy, we posit that there is a benefit of a reduced working memory load for the detector resulting in more accurate search. This paradigm creates a counterintuitive speed/accuracy trade-off which combines the heightened ability that comes from task experience (discrimination task) with the slower performance times associated with a novel task (the initial search) to create a potentially more efficient method of visual search.     

Interindividual differences among native right-to-left readers and native left-to-right readers during free viewing task

Human visual exploration is not homogeneous but displays spatial biases. Specifically, early after the onset of a visual stimulus, the majority of eye movements target the left visual space. This horizontal asymmetry of image exploration is rather robust with respect to multiple image manipulations, yet can be dynamically modulated by preceding text primes. This characteristic points to an involvement of reading habits in the deployment of visual attention. Here, we report data of native right-to-left (RTL) readers with a larger variation and stronger modulation of horizontal spatial bias in comparison to native left-to-right (LTR) readers after preceding text primes. To investigate the influences of biological and cultural factors, we measure the correlation of the modulation of the horizontal spatial bias for native RTL readers and native LTR readers with multiple factors: age, gender, second language proficiency, and age at which the second language was acquired. The results demonstrate only weak or no correlations between the magnitude of the horizontal bias and the previously mentioned factors. We conclude that the spatial bias of viewing behaviour for native RTL readers is more variable than for native LTR readers, and this variance could not be demonstrated to be associated with interindividual differences. We speculate the role of strength of habit and/or the interindividual differences in the structural and functional brain regions as a cause of the RTL spatial bias among RTL native readers.     

The power of the imagination to affect peripersonal space representations

It is known that visual processing is altered for objects near the hands as well as for objects near the imagined position of the hands, indicating that the imagination can be used to remap peri-hand space. Little is known, however, about the physical conditions that allow for this remapping. In the present study, participants in one experiment performed visual searches through displays that were beyond reach while imagining that their hands were near the display. This imagined impossible posture slowed visual search rates, showing that imagination effectively remapped peri-hand space to be near the display. In another experiment, participants searched displays they were holding, but sometimes imagined their hands to be far away. This produced faster search rates, revealing a remapping of peri-hand space away from the monitor. The results provide new insights into the mechanisms involved in the representation of peri-hand space and about the power of imagined actions to influence body representations.     

Withdrawal of spatial overt attention following intentional forgetting: evidence from eye movements

Eye movements were measured to examine whether item-method directed forgetting involved a spatial overt attention shift. Experiment 1 showed that participants’ eyes were moved away from the study word following the forget and ignore cues, but not the remember cue. Experiment 2 revealed that the eyes were moved away from the area that covered by the study word even when the study word disappeared upon the presentation of the memory cue. Both the study word and memory cue were presented auditorily in Experiment 3. In all experiments, the to-be-remembered words were recalled better than both to-be-forgotten and to-be-ignored words. More importantly, mental effort, as indexed by the pupil size, increased following the remember, as compared with the forget and ignore cues. These findings are discussed in terms of controlling spatial overt attention after encoding to withdraw attention from irrelevant information and to allocate cognitive resources to relevant information for long-term retention.