Effects of Backpack Carriage on Dual-Task Performance in Children During Standing and Walking

Primary school children perform parts of their everyday activities while carrying school supplies and being involved in attention-demanding situations. Twenty-eight children (8–10 years old) performed a 1-legged stance and a 10 m walking test under single- and dual-task situations in unloaded (i.e., no backpack) and loaded conditions (i.e., backpack with 20% of body mass). Results showed that load carriage did not significantly influence children's standing and walking performance (all p > .05), while divided attention affected all proxies of walking (all p < .001). Last, no significant load by attention interactions was detected. The single application of attentional but not load demand negatively affects children's walking performance. A combined application of both did not further deteriorate their gait behavior.     

The Impact of Strategic Trajectory Optimization on Illusory Target Biases During Goal-Directed Aiming

During rapid aiming, movements are planned and executed to avoid worst-case outcomes that require time and energy to correct. As such, downward movements initially undershoot the target to avoid corrections against gravity. Illusory target context can also impact aiming bias. Here, the authors sought to determine how strategic biases mediate illusory biases. Participants aimed to Müller-Lyer figures in different directions (forward, backward, up, down). Downward biases emerged late in the movement and illusory biases emerged from peak velocity. The illusory effects were greater for downward movements at terminal endpoint. These results indicate that strategic biases interact with the limb-target control processes associated with illusory biases. Thus, multiple control processes during rapid aiming may combine and later affect endpoint accuracy (D. Elliott et al., 2010 Elliott, D., Hansen, S., Grierson, L. E. M., Lyons, J., Bennett, S. J., &; Hayes, S. J. (2010). Goal-directed aiming: two components but multiple processes. Psychological Bulletin, 136, 1023–1044.[Crossref], [PubMed], [Web of Science ®] , [Google Scholar]).     

Roles of Visual Information for Control of Reaching Movements in Children

Poststroke hemiparetic individuals (n = 9) and a control group (n = 9) completed a frequency-scaled circle-drawing task in unimanual and bimanual conditions. Measures of intralimb spatial and temporal task accuracy and interlimb coordination parameters were analyzed. Significant reductions in task performance were seen in both limbs of the patients and controls with the introduction of bimanual movement. Spatial performance parameters suggested that the 2 groups focused on different hands during bimanual conditions. In the controls, interlimb coordination variables indicated predictable hand dominance effects, whereas in the patient group, dominance was influenced by the side of impairment and prior handedness of the individual. Therefore, in this particular bimanual task, performance improvements in the hemiplegic side could not be elicited. Intrinsic coupling asymmetries between the hands can be altered by unilateral motor deficits.     

Evidence Supporting the Importance of Peripheral Visual Information for the Directional Control of Aiming Movement

The focus of the present study was on determining whether the high level of directional accuracy found in aiming studies in which the subjects can see their hand in the visual periphery supports the existence of a kinetic visual channel or, rather, the advantage of binocular over monocular vision for movement directional control. The limits of this kinetic visual channel were also explored. The results of the 1st experiment indicated that seeing one's hand in the visual periphery is sufficient to ensure optimal directional aiming accuracy. Further, no differences in aiming accuracy were noted between monocular and binocular vision. These results supported the existence of a visual kinetic channel. In the 2nd experiment, whether this kinetic visual channel would operate with movements slower (55°/s) than those usually used in studies that had proved its existence (over 110°/s) was determined. The results indicated that this visual kinetic channel was operative even at relatively slow movement velocities. Central vision of the hand seemed to be used for on-line directional control of relatively slow movements.     

Biomechanical Study of Tandem Stance in Healthy Young Adults: Effects of Weight-Bearing and Limb Dominance

Postural strategies of healthy young adults to control tandem stance were investigated through the calculation of the relative contribution of the two loading-unloading (LU) and pressure-distribution (PD) mechanisms and the two legs for controlling the resultant center-of-pressure (CP_Res) displacements. Weight-bearing asymmetry and limb dominance were also studied. For antero-posterior and medio-lateral CP_Res displacements, LU and PD mechanisms mainly contribute, respectively. A significant LU contribution is nonetheless observed for medio-lateral control, due to a lateral gap between the CP positions under each foot despite a strict sagittal alignment for the two feet. Moreover, for medio-lateral control, the respective involvement of the two legs is related to the level of weight-bearing asymmetry, whereas the front leg mainly controls the antero-posterior sway. By specifying potential effects of body-weight asymmetry and limb dominance, to a better testing of patients with deficiencies in lateral sway control.     

The Effect of Posture on Early Reaching Movements

Infants of about 5 months of age who have just mastered the ability to reach succeed more frequently in contacting an object when they are seated upright than when they are supine or reclined. That effect of posture disappears in the subsequent months. Whether that effect can be attributed either to insufficient muscular strength or to insufficient control over the mechanically unstable arm was the subject of the present investigation. Kinematics and electromyography (EMG) of reaching movements of 8 sitting and supine infants at 12, 16, and 20 weeks of age were recorded. Maximum levels of shoulder torque as well as kinematic stability measures were similar in both postures. Coactivation levels and the frequency of on-off switching of muscles turned out to be higher in the sitting than in the supine posture. The authors suggest that the difference in reaching behavior resulted from the degree of error in the feedforward control signal that was allowed by the different postures rather than either insufficient muscular strength or insufficient control over the mechanically unstable arm.     

‘Ought’ and Control

Ethical theorists often assume that the verb ‘ought’ means roughly ‘has an obligation’; however, this assumption is belied by the diversity of ‘flavours’ of ought-sentences in English. A natural response is that ‘ought’ is ambiguous. However, this response is incompatible with the standard treatment of ‘ought’ by theoretical semanticists, who classify ‘ought’ as a member of the family of modal verbs, which are treated uniformly as operators. To many ethical theorists, however, this popular treatment in linguistics seems to elide an important distinction between agential and non-agential ought-statements. The thought is that ‘ought’ must have at least two senses, one implicating agency and connected to obligations, and another covering other uses. In this paper, I pursue some resolution of this tension between semantic theory and ethical theory with respect to the meaning of ‘ought’. To this end, I consider what I believe to be the most linguistically sophisticated argument for the view that the word ‘ought’ is ambiguous between agential and non-agential senses. This argument, due to Mark Schroeder, is instructive but based on a false claim about the syntax of agential ought-sentences—or so I attempt to show by first situating Schroeder's argument in its proper linguistic background and then discussing some syntactic evidence that he fails to appreciate. Then, I use the failure of this argument to motivate some more general reflections on how the standard treatment of ‘ought’ by theoretical semanticists might be refined in the light of the distinction important to ethical theory between agential and non-agential ought-statements, but also on how ethical theory might benefit from more careful study of the dominant treatment of modals as operators in theoretical semantics.     

Grip Control in Children before,during, and after Impulsive Loading

The manipulation of small objects requires continuous contributions from both predictive and reactive mechanisms. The authors aimed to study the development of predictive and reactive mechanisms used by children from 6 to 14 years of age to manage impulsive loading. The load of a handheld object was increased rapidly by the drop of a weight hung on the object. The drop was triggered either by the child (predictive condition) or by the examiner (reactive condition). Regardless of the condition, the control strategy was refined with age. Younger children were unable to adapt their grip force (GF) to the friction of their fingers, whereas the older children provided GF that was well adapted to their variable coefficient of friction, thereby producing a secure grip. This reflected either an inadequate amount of force or an inability to integrate cutaneous information from the fingers in younger children. Additionally, a modulation with age for both predictive and reactive mechanisms was observed. All together, the better predictive abilities and the more secure grip exhibited by older children allow decreased slipping and improved performance in an impulsive loading task.