Postintentional Neglect

F. Mechsner (2004) seems to deny a functional importance of postintentional processes, except that their characteristics can be taken into account at the perceptual-cognitive level of control. In that perspective, processes that are critical for the understanding of motor control and its limitations are neglected. On the other hand, the functional importance of task conceptions or task sets, which can vary and affect performance even for tasks that appear identical to an observer, is emphasized.     

On the Hand Transport Component of Prehensile Movements

Jeannerod (1981) proposed that prehensile movements involve two independent visuomotor channels that are responsible for hand transport and hand aperture. In many studies, the movement of a marker placed on the wrist has been used as an index of hand transport because wrist movement is unaffected by the movements of the digits responsible for hand aperture. In the present study, the spatial paths of the wrist, index finger, and thumb of 5 adults, each performing 50 reaching movements, were measured with a WATSMART movement tracking system, and their variability was analyzed. The measures of movement variability suggest that the motor system is more concerned with thumb position than with wrist position during hand transport. Although the wrist is a technically convenient index of hand transport, the thumb may be a more appropriate index from the point of view of motor control.     

Perturbations in Action Goal Influence Bimanual Grasp Posture Planning

The authors examined the effects of perturbations in action goal on bimanual grasp posture planning. Sixteen participants simultaneously reached for 2 cylinders and placed either the left or the right end of the cylinders into targets. As soon as the participants began their reaching movements, a secondary stimulus was triggered, which indicated whether the intended action goal for the left or right hand had changed. Overall, the tendency for a single hand to select end-state comfort compliant grasp postures was higher for the nonperturbed condition compared to both the perturbed left and perturbed right conditions. Furthermore, participants were more likely to plan their movements to ensure end-state comfort for both hands during nonperturbed trials, than perturbed trials, especially object end-orientation conditions that required the adoption of at least one underhand grasp posture to satisfy bimanual end-state comfort. Results indicated that when the action goal of a single object was perturbed, participants attempted to reduce the cognitive costs associated with grasp posture replanning by maintaining the original grasp posture plan, and tolerating grasp postures that result in less controllable final postures.     

Moving memories: Behavioral synchrony and memory for self and others

Establishing and maintaining connections with others is central to a fulfilling social life. In this respect, behavioral coordination provides one avenue by which interpersonal linkages can be formed. Drawing from the dynamical systems approach, the present research explored whether temporary interpersonal connections founded on coordinated behavior influence memory for self and others. To do so, we measured participants’ incidental recall of self and other-relevant information after a period of either in-phase or anti-phase interpersonal coordination. While participants in the less stable anti-phase condition demonstrated the typical memory advantage for self-related compared to other-related information, this effect was eliminated when participant and confederate movements displayed in-phase coordination. These results are discussed with respect to the interplay between the systems that support interpersonal synchrony and basic social-cognitive processing.     

Motion coordination affects movement parameters in a joint pick-and-place task

This study examined influences of social context on movement parameters in a pick-and-place task. Participants' motion trajectories were recorded while they performed sequences of natural movements either working side-by-side with a partner or alone. It was expected that movement parameters would be specifically adapted to the joint condition to overcome the difficulties arising from the requirement to coordinate with another person. To disentangle effects based on participants' effort to coordinate their movements from effects merely due to the other's presence, a condition was included where only one person performed the task while being observed by the partner. Results indicate that participants adapted their movements temporally and spatially to the joint action situation: Overall movement duration was shorter, and mean and maximum velocity was higher when actually working together than when working alone. Pick-to-place trajectories were also shifted away from the partner in spatial coordinates. The partner's presence as such did not have an impact on movement parameters. These findings are interpreted as evidence for the use of implicit strategies to facilitate movement coordination in joint action tasks.     

临时知识型员工自主性动机激发：关系导向人力资源管理建构及其作用机理

快速变化的技术需求使得人才外部化, 人才共享成为组织获取技能型、知识型人才的重要方式。共享经济背景下的人力资源管理属于新兴研究领域, 企业在管理临时知识型员工面临很大挑战。由于身份的外部性、临时性, 员工关系基础薄弱, 临时知识型员工专业能力发挥受限, 工作场所关系需求受阻, 导致自主性动机不足, 影响绩效产出, 而传统对外部员工的契约型管理难以解决以上问题。针对嵌入团队工作的临时知识型员工, 研究基于关系型协调理论探索关系导向人力资源管理实践构成。在此基础上, 结合自我决定理论探讨关系导向人力资源管理实践提升临时知识型员工绩效的作用机理, 验证从自主性动机来源、自主性动机激发到自主性动机结果的路径机制。对关系导向人力资源管理实践内容和效用探讨有助于深入理解临时知识型员工的管理, 为共享经济背景下新型用工管理实践提供启示。     

Auditory information is beneficial for adults with Down syndrome in a continuous bimanual task

Much recent research using discrete unimanual tasks has indicated that individuals with Down syndrome (DS) have more difficulty performing verbal-motor tasks as compared to visual-motor tasks (see Perceptual-Motor Behavior in Down Syndrome, Human Kinetics, Champaign, IL, 2000, p. 305 for a review). In continuous tasks, however, individuals with DS perform better when movement is guided by auditory information compared to visual information (Downs Syndr.: Res. Prac. 4 (1996) 25; J. Sport Exercise Psy. 22 (2000) S90). The aim of the present study was to investigate if there are any differences for adults with DS between visual, auditory and verbal guidance in a continuous bimanual task. Ten adults with DS, 10 adults without DS and 10 typically developing children drew lines bimanually towards the body (down) and away from the body (up) following three different guidance conditions: visual (flashing line), auditory (high tone, low tone), and verbal (“up”, “down”). All participants produced mostly in-phase movements and were close to the 1000 ms target time for all guidance conditions. The adults with DS, however, displayed greater variability in their movement time, movement amplitude and bimanual coordination than adults without DS. For all groups, the left hand was slower and more variable in producing the lateral movements than the right hand. The results regarding guidance information suggest that auditory information is beneficial for repetitive bimanual tasks for adults with DS. Possible mechanisms that cause these results will be discussed.     

Coordination deficits on the ipsilesional side after unilateral stroke: the effect of practice on nonisodirectional ipsilateral coordination

Previous studies have identified motor deficits on the ipsilesional side of patients recovering from a cerebro-vascular accident (CVA), including deficits in interlimb coordination. In the present study, unilateral stroke patients and a control group of healthy age-matched controls performed nonisodirectional coordination of the ipsilateral limbs across two days of practice with feedback. Findings revealed that control subjects were already quite successful at initiation of practice but further improved the coordination pattern across both days. The group of CVA patients also showed some improvement but problems with coordination of the ipsilateral limb segments persisted across practice. Variability in both timing and amplitude of both limb segments did improve with practice in both groups but these measures remained significantly higher in the CVA patients. Even though isodirectional and nonisodirectional coordination of the ipsilateral limb segments are normally considered to be part of the intrinsic motor repertoire, the present study suggests that nonisodirectional ipsilesional limb coordination poses considerable difficulties for CVA patients that are not easily overcome with feedback-assisted practice.     

Influences of handedness and gender on the grooved pegboard test

We studied performance on the Grooved Pegboard Test upon repeated trials and transfer of training between the hands in the first trial. The classification of handedness was based on the writing hand. We employed three trials for each hand and two different protocols for the order in which the hands started the test. For the three trials combined, women were faster than men. From the first to the second trial, there was an improvement in performance for both sexes. Within the first trial, sex differences reached significance and the protocol interacted with handedness. In this trial, only left-handed men were found to benefit from previous opposite-hand performance. It is speculated that a larger corpus callosum in left-handed men allows for the greater transfer of training between the hands.