Standing Posture on Land and at Sea

We studied the influence of ship motion on postural activity during stance, varying stance width (the distance between the feet in side-by-side stance) and the difficulty of visual tasks. Participants (experienced crewmembers) were tested on land and then on successive days on a ship at sea in mild sea states. On land, we replicated classical effects of stance width and visual task on the magnitude of postural movement. The magnitude of forces used in postural control was greater at sea than on land. Visual performance at sea was comparable to performance on land. Both stance width and visual task difficulty influenced postural activity at sea. In addition, postural activity changed over days at sea. We conclude that experienced crewmembers modulated standing posture in support of the performance of visual tasks and that such effects occurred even in mild sea states. The overall pattern of effects is compatible with the hypothesis that postural activity is modulated, in part, in support of the performance of suprapostural tasks.     

Postural Sway and the Amplitude of Horizontal Eye Movements

In 2 experiments, we evaluated relations between postural activity and the amplitude of visually guided eye movements. Participants shifted their gaze to follow horizontal oscillation of a visible target. The target moved with amplitude 9° or 24°. In different experiments, the frequency of target oscillation was 0.5 Hz or 1.1 Hz. In both experiments, the variability of head and torso motion was reduced (in the anterior-posterior axis) when participants viewed moving targets, relative to sway during viewing of stationary targets. Sway variability was not influenced by the amplitude of target motion. The results are compatible with the hypothesis that postural activity was modulated relative to the demands of suprapostural visual tasks.     

Effects of the orientation of moving objects on the perception of streaming/bouncing motion displays

In this study, we examined the contribution of the orientation of moving objects to perception of a streaming/bouncing motion display. In three experiments, participants reported which of the two types of motion, streaming or bouncing, they perceived. The following independent variables were used: orientation differences between Gabor micropatterns (Gabors) and their path of motion (all the experiments) and the presence/absence of a transient tone (Experiment 1), transient visual flash (Experiment 2), or concurrent secondary task (Experiment 3) at the coincidence of Gabors. The results showed that the events at coincidence generally biased responses toward the perception of bouncing. On the other hand, alignment of Gabors with their motion axes significantly reduced the frequency of bounce perception. The results also indicated that an object whose orientation was parallel to its motion path strengthened the spatiotemporal integration of local motion signals along a straight motion path, resulting in the perception of streaming. We suggest that the effect of collinearity between Gabors and their motion path is relatively free from the effect of attention distraction.     

Learning to coordinate redundant degrees of freedom in a dynamic balance task

The present study investigated Bernstein's [The co-ordination and regulation of movements, 1967] proposal regarding the three stages of learning in the changing coordination and control of redundant joint-space degrees of freedom. Six participants practiced maintaining balance on a moving platform that was sinusoidally translated in the anterior-posterior direction for 30 trials on day 1 and 10 trials on day 2. At the beginning of practice, the motion of the torso and limb segments was less coherent in the attempt to compensate for the movement of the support surface in retaining a balanced posture. However, with practice, the organization of a compensatory postural coordination mode became highly coherent and also progressively utilized the passive, inertial forces generated by the movement of the support surface. The findings support the propositions that: (a) the pathway of change over time in the coordination pattern of the torso and joint motions depends on the task goal and constraints to action and (b) the changes in limb and torso motion are in support of the learning of a global body center of mass/platform dynamic.     

The Role of Visual Feedback about Motion of the Ground on Postural Sway

Abstract

We asked whether body sway would be influenced by visual information about motion of the ground surface. On a ship at sea, standing participants performed a demanding visual search task or a simple visual inspection task. Display content was stationary relative to the ship or relative to the Earth. Participants faced the ship’s bow or its port side. Performance on the visual search task was representative of terrestrial studies. Body sway was greater during viewing of the Earth Stationary displays than during viewing of the Ship Stationary displays. We discuss possible implications of these results for theoretical and applied issues.     

The Effects of Attentional Focus Instructions and Task Difficulty in a Paced Fine Motor Skill

Abstract

An external focus of attention is considered superior to an internal focus for learning and performance. However, findings specific to changing the task difficulty are inconsistent. The present study used a reciprocal aiming task to determine the effects of attentional focus on motor performance using speed-accuracy paradigm. We constrained timing to examine how internal and external focus of attention influenced accuracy when task difficulty changes. The results indicated greater accuracy on the right target and greater consistency on both targets for the external focus condition, regardless of task difficulty. Our results uniquely demonstrated how instruction modified a speed-accuracy task.     

Reward Influence on the Heart: Cardiovascular Response as a Function of Incentive Value at Five Levels of Task Demand

This study examined cardiovascular effects of incentive value in men and women confronted with cognitive challenges that were more and less difficult to meet. Participants performed computer memory tasks varying in difficulty from low to high, with instructions that they could earn chances toward a $100 prize or $10 prize by attaining a 90% success rate. Analysis of cardiovascular responses assessed during work revealed an interaction between difficulty and incentive value for heart rate. Participants' heart rate responses were proportional to task difficulty and unaffected by incentive value in all conditions except for the most difficult one. Where difficulty was greatest, $100 participants showed relatively high heart rate responsiveness, whereas $10 participants showed low heart rate responsiveness. This heart rate finding corroborates and extends cardiovascular results from previous experiments, and lends further support to the view that cardiovascular responses will be proportional to incentive value only under some task conditions.     

Effects of dual task difficulty in motor and cognitive performance: Differences between adults and adolescents

In the present study our aim was to compare dual-task performance in thirteen adolescents and fifteen young adults while concurrently performing a cognitive and a motor task. The postural control variables were obtained under three different conditions: i) bipedal stance, ii) tandem stance and iii) unipedal stance. The cognitive task consisted of a backward digit span test in which the participants were asked to memorize a sequence of numbers and then repeat the number in reverse order at three different difficulty levels (i.e. with 3, 4 and 5 digits). The difficulty of the cognitive task was seen to have different effects on adolescents and young adults. Adolescents seem to prioritize postural control during high difficulty postural conditions while a cross-domain competition model appeared in easy postural conditions.     

Task difficulty and inertial properties of hand-held tools: An assessment of their concurrent effects on precision aiming

Aiming hand-held tools at targets in space entails adjustments in the dynamical organization of aiming patterns according to the required precision. We asked whether and how these adjustments are modified by the tool’s mass distribution. Twelve participants performed reciprocal aiming movements with a 50-cm long wooden probe. Kinematic patterns of probe movements were used as a window into the behavioral dynamic underlying performance of a reciprocal aiming task. We crossed three levels of task difficulty (IDs 2.8, 4.5 and 6.1) with two types of probe varying in their mass distribution (proximal vs distal loading). Movement duration was affected by task difficulty and probe loading (shorter for larger targets and proximal probe loading). Progressive deviations from a sinusoidal movement pattern were observed as task difficulty increased. Such deviations were more pronounced with proximal probe loading. Results point to a higher degree of non-linearity in aiming dynamics when the probe was loaded proximally, which might reflect employment of additional perceptual-motor processes to control the position of its less stable tip at the vicinity of the targets. More generally, the effects of probe loading on aiming pattern and dynamics suggest that perceptual-motor processes responding to task level constraints are sensitive to, and not independent from, biomechanical, end-effector constraints.     

Influence of Complexity and Coupling of Optic Flow on Visually Induced Motion Sickness

Postural stability is critical for our ability to engage in other behaviors and can be influenced by several factors, including changes in optic flow. In situations where postural stability is degraded for prolonged periods of time, motion sickness commonly results. The current research examined how the complexity of a motion stimulus and the coupling of a motion stimulus to the actions of the participant influenced postural sway and motion sickness. Differences in incidence of motion sickness and postural sway characteristics emerged across conditions. In particular, postural sway of participants who became motion sick was characterized by increases in magnitude and spatial complexity but by a decrease in temporal complexity compared with participants who remained well.     

Attention is required for maintenance of feature binding in visual working memory

Working memory and attention are intimately connected. However, understanding the relationship between the two is challenging. Currently, there is an important controversy about whether objects in working memory are maintained automatically or require resources that are also deployed for visual or auditory attention. Here we investigated the effects of loading attention resources on precision of visual working memory, specifically on correct maintenance of feature-bound objects, using a dual-task paradigm. Participants were presented with a memory array and were asked to remember either direction of motion of random dot kinematograms of different colour, or orientation of coloured bars. During the maintenance period, they performed a secondary visual or auditory task, with varying levels of load. Following a retention period, they adjusted a coloured probe to match either the motion direction or orientation of stimuli with the same colour in the memory array. This allowed us to examine the effects of an attention-demanding task performed during maintenance on precision of recall on the concurrent working memory task. Systematic increase in attention load during maintenance resulted in a significant decrease in overall working memory performance. Changes in overall performance were specifically accompanied by an increase in feature misbinding errors: erroneous reporting of nontarget motion or orientation. Thus in trials where attention resources were taxed, participants were more likely to respond with nontarget values rather than simply making random responses. Our findings suggest that resources used during attention-demanding visual or auditory tasks also contribute to maintaining feature-bound representations in visual working memory—but not necessarily other aspects of working memory.     

The effects of background visual roll stimulation on postural and manual control and self-motion perception

The effects of background visual roll stimulation on postural control, manual controlf andselfmotion perception were investigated in this study. In the main experiment, 8 subjects were exposed to wide field-of-view background scenes that were tilted and static, continuously rotating, or sinusoidally rotating at frequencies between 0.03 and 0.50 Hz, as well as a baseline condition. The subjects performed either a postural control task (maintain an upright stance) or a manual control task (keep an unstable central display horizontally level). Root-mean square (RMS) error in both the postural and manual control tasks was low in the static tilt condition and extremely high in response to continuous rotation. Although the phases of the postural and manual responses were highly similar, the power and RMS error generated by the sinusoidal visual background stimulation peaked at a lower frequency in the postural task. Vection ratings recorded at the end of the postural and manual trials somewhat paralleled tbafrequency tuning differences between tasks, which a subsequent experiment showed to be the result of the differential motion of the central display rather than the differential positioning of the subject. In general, these results show that the dynamic characteristics of visual orientation systems vary according to the specific motor and/or perceptual system investigated.     

Postural coordination modes considered as emergent phenomena.

The coordination of multiple body segments (torso and legs) in the control of standing posture during a suprapostural task was studied. The analysis was motivated by dynamical theories of motor coordination. In 2 experiments it was found that multisegment postural coordination could be described by the relative phase of rotations around the hip and ankle joints. The effective length of the feet, the height of the center of mass, and the amplitude of head motions in a visual tracking task were varied. Across these variations, 2 modes of hip-ankle coordination were observed: in-phase and anti-phase. The emergence of these modes was influenced by constraints imposed by the suprapostural tracking task, supporting the idea that such tasks influence postural control in an adaptive manner. Results are interpreted in terms of a dynamical approach to coordination in which postural coordination modes can be viewed as emergent phenomena.     

Not just standing there: the use of postural coordination to aid visual tasks

Postural control is an integral part of all physical behavior. Recent research has indicated that postural control functions in a manner that facilitates other higher order (suprapostural) tasks. These studies, while showing that postural sway is modulated in a task specific manner, have not examined the form of postural coordination that allows for the achievement of these higher behavioral goals. The current study examined the relation between visual task constraints (viewing distance), environmental constraints (changes in the surface of support), and the postural coordination employed to complete the task. Thirty-one participants were asked to perform a reading task while standing on various surfaces. Postural motion was recorded from the head, cervico-thoracic spine, sacrum (hip), and ankle. It was found that body segment coordination changed as a function of surface characteristics and task constraints. Additionally, the overall pattern of postural sway (head motion) replicated that which was found by Stoffregen et al. [J. Exp. Psychol. Human Percep. Perform. 25 (6) (1999) 1641]. These findings suggest that postural adaptation involves more than basic reduction or increase of motion; it involves the functional coordination of body segments to achieve a particular goal. The data further suggest that there is a need to examine postural control in the absence of external perturbations.     

Achievement goals, task performance, and interest: why perceived goal difficulty matters

In field studies, mastery goals, which focus on developing skill, often predict task interest but not actual performance. Performance-approach goals, which focus on outperforming others, instead often predict strong performance but not interest. Two experiments tested the hypothesis that these distinct goal effects trace to goal difficulty perceptions. In each study, participants assigned to a performance-approach goal perceived their goal to be harder, and therefore felt more performance pressure, than those assigned to a mastery goal. Among participants low in dispositional achievement orientation, this experience translated into lower task interest when pursuing the performance-approach goal. However, participants in both studies also performed the activity better when pursuing this goal instead of a standard mastery goal, although this was not mediated by self-reported goal difficulty perceptions. Finally, further demonstrating the role of goal difficulty, a mastery goal manipulated to appear more difficult than a standard mastery goal produced effects matching the performance-approach goal.     

Attentional Demands Associated With Postural Control Depend on Task Difficulty and Visual Condition

The authors aimed to assess the effect of vision on variations in attentional resources allocated to postural control during tasks of various levels of difficulty. Test-retest reliability of postural and cognitive parameters was also evaluated. Twenty adults stood quietly on a force platform during 30-s trials (primary task). Twelve conditions involving combinations of three bases of support, two vision conditions, and the presence or absence of a simple reaction time task (secondary task) were tested. Baseline trials of the reaction time task were also performed with the participants seated. Reaction time and postural parameters demonstrated good to excellent test-retest reliability in most conditions. Postural control was altered by the reduction of the base of support and by the absence of vision. Maintaining an upright stance increased reaction time compared with a seated position, indicating that quiet standing tasks required some attention even in young adults. Changes in postural steadiness were correlated with changes in reaction time, showing a significant relationship between the difficulty of the postural task and the attentional resources allocated to postural control. However, reaction time increased with the reduction of the base of support only without vision. This dual task paradigm showed that vision can compensate for the increase in attentional demands during the most difficult postural tasks.     

To err is human: How regulatory focus and action orientation predict performance following errors

In the current study, we hypothesize that post-error performance is influenced by individual differences in action orientation and situationally induced regulatory focus. Two experiments employing a time-pressured flanker-like task, measured participants’ dispositional action orientation and manipulated regulatory focus. As expected, accuracy of the responses following errors was reduced for all participants except for action-oriented participants in a promotion focus. The latter participants are assumed to down-regulate error-related negative affect, thereby saving resources for subsequent performance. A promotion focus is assumed to facilitate the optimal use of these resources.     

A test of engagement versus disengagement in catastrophe models

The present study explored the interactive effects of self‐efficacy and increasing/decreasing task difficulty upon engagement and disengagement within a cusp‐catastrophe model framework. Using a closed motor skill aiming task participants (N=60) were required to compete in conditions where task difficulty increased and then decreased (or vice versa) where they were rewarded for good performance but penalized for bad. Participants who reported low levels of self‐efficacy disengage at an earlier level of task difficulty than their high self‐efficacy counterparts. Furthermore, this group did not re‐engage with the task until task difficulty had significantly decreased. Although task disengagement occurred with high difficulty in the high self‐efficacy group, this group re‐engaged in a similar manner in which they disengaged. Findings support and extend those of previous tests of catastrophe models by directly allowing for task disengagement.     

Cognitive engagement in emotional text reading: concurrent recordings of eye movements and head motion

ABSTRACT

The present study examined the effects of emotions on eye movements, head motion, and iPad motion during reading. Thirty-one participants read neutral, emotionally negative texts and emotionally positive texts on a digital tablet and both participants’ eye movements and body movements were recorded using respectively eye-tracking glasses and a motion capture system. The results showed that emotionally positive texts were read faster than neutral texts, and that readers’ movements decreased when reading emotional texts regardless of valence polarity. Recent studies suggested that postural movements may reflect cognitive engagement and especially the engagement in the task to be done. Our findings seem to validate this hypothesis of a bodily engagement in reading emotional contents. The present results suggest that the novel methodology of eye and postural movement recordings is informative in studying the readers’ embodied engagement during reading emotional materials.     

Postural stabilization for the control of touching

We attempted to distinguish between task-related (supra-postural) and perceptual influences on postural motions. Two groups of participants had to make very light tactile contact with an adjacent pliable surface while standing with their eyes closed. In the absence of vision, such light touching with a finger is known to reduce sway. For one group, tactile contact with the surface was merely the result of extending the right forearm. For the other group, variability in the point of tactile contact had to be kept to a minimum. Touching reduced postural sway relative to non-touching only for participants in the latter group. The present results, in combination with others addressing similar task differences, question the assumption that information detected haptically and/or visually is used solely to reduce postural fluctuations. It seems that postural fluctuations are modulated to facilitate performance of tasks over and above the task of standing upright and still.