Rack-and-pinion effects in molecular rolling friction

Rolling lubrication with spherical molecules working as ‘nanobearings’ has failed experimentally so far, without a full understanding of the physics involved and of the reasons why. Past model simulations and common sense have shown that molecules can only roll when they are not too closely packed to jam. The same type of model simulations now shows in addition that molecular rolling friction can develop deep minima once the molecule's peripheral ‘pitch’ can match the substrate periodicity, much as ordinary cogwheels do in a rack-and-pinion system. When the pinion-rack matching is bad, the driven molecular rolling becomes discontinuous and noisy, whence energy is dissipated and friction is large. This suggests experiments to be conducted by varying the rack-and-pinion matching. That could be pursued not only by changing molecules and substrates, but also by applying different sliding directions within the same system, or by applying pressure, to change the effective matching.     

EDITORIAL COMMENT: GUEST COMMENTARY

A pervasive problem faced by children in both classroom and clinic is the lack of transfer from the apparent learning of “skills” to improved overall reading performance. For varied reasons, “skills” learned by children fail to become integrated to enhance reading fluency. A related problem derives from the lack of automaticity that many children fail to achieve either in specific facilitating “skills” or in the reading task generally.     

From outcome prediction to action selection: developmental change in the role of action–effect bindings

Ideomotor theory considers bidirectional action–effect associations to be the fundamental building blocks for intentional action. The present study employed a novel pupillometric and oculomotor paradigm to study developmental changes in the role of action‐effects in the acquisition of voluntary action. Our findings suggest that both 7‐ and 12‐month‐olds (and adults) can use acquired action–effect bindings to predict action outcomes but only 12‐month‐olds (and adults) showed evidence for employing action‐effects to select actions. This dissociation supports the idea that infants acquire action–effect knowledge before they have developed the cognitive machinery necessary to make use of that knowledge to perform intentional actions.     

Athletes' inclination to play through pain: a coping perspective

Previous studies have shown how social networks lead athletes to accept pain as a “part of the game,” which generates pressure on athletes to continue competing despite being in pain. Little is known, however, about the potential coping strategies that are related to pain behavior in sport. This study of 205 combat athletes examined whether pain coping strategies, including distraction from pain, praying, reinterpreting pain sensations, ignoring pain, and pain catastrophizing, are related to athletes’ inclination to play through pain. Results revealed that pain catastrophizing led athletes to reduce their physical involvement in their sport activity. Of particular interest was the moderating effect of ignoring pain such that ignoring pain significantly attenuated the negative effect of pain intensity on athletes’ inclination to play through pain. Few studies have tested and supported the contribution of pain coping to the prediction of behavior in real sport situations. By identifying which coping strategies athletes could use to maintain their physical involvement despite being in (sometimes intense) pain, the current study makes an important contribution for tailoring pain management programs for this at-risk population.     

Assessing the Level of Structural Integration Using Operationalized Psychodynamic Diagnosis (OPD): Implications for DSM–5

In order to investigate the state-trait anxiety distinction in emotionally disturbed and normal children, the responses of 120 emotionally disturbed children and 126 normal children to the State-Trait Anxiety Inventory for Children (Spielberger, 1973) were factor analyzed separately. For the emotionally disturbed group two A-State and two A-Trait factors were found with the A-State factors accounting for significantly more of the variance than did A-Trait factors. For the normal group four A-State and two A-Trait factors were found, but there was not a significant difference between the amount of variance accounted for by A-State and A-Trait factors. Results were discussed as supporting the state-trait distinction and as having several implications for future research on anxiety.     

Spatial Conceptual Influences on the Coordination of Bimanual Actions: When a Dual Task Becomes a Single Task

When the left and right hands produce 2 different rhythms simultaneously, coordination of the hands is difficult unless the rhythms can be integrated into a unified temporal pattern. In the present study, the authors investigated whether a similar account can be applied to the spatial domain. Participants (N = 8) produced a movement trajectory of semicircular form in single-limb and bimanual conditions. In the bimanual tasks, 1 limb moved above the other in the frontal plane. Bimanual unified tasks were constructed so that the spatial paths to be produced by the 2 limbs could be easily conceptualized as parts of a unified circle pattern. Bimanual distinct tasks availed a less obvious spatial pattern that would unify the 2 tasks. Performance of the spatial patterns was more accurate in the unified task, despite similar demands placed on the coordination dynamics between the limbs in the 2 cases (e.g., the phase relations). The authors conclude that a dual task becomes a single task, and interlimb interference is reduced, when the spatial patterns produced by the 2 hands form a geometric arrangement that can be conceptualized as a unified representation.     

Bimanual Training Reduces Spatial Interference

The authors investigated whether training can reduce bimanual directional interference by using a star-line drawing paradigm, Participants (N = 30) were required to perform rhythmical arm movements with identical temporal but differing directional demands. Moreover, the effectiveness of part-task training in which each movement was practiced in isolation was compared with that of whole-task training in which only combined movements were performed. Findings revealed that bimanual training substantially reduced spatial interference, but unimanual training did not. The authors therefore concluded that the spatial coupling of the limbs is not implemented in a rigid way; instead, the underlying neural correlate can undergo plastic changes induced by training. Moreover, the practical implication that emerged from the present study is that athletic, musical, or ergonomic skills that require a high degree of interlimb coordination are best served by whole-task practice.     

Technology and Older Adults: Factors Affecting the Adoption of Automatic Teller Machines

Although technology can benefit service providers, caregivers, and the elderly, its application in an aging society can bring special challenges. This study looked at older adults' adoption of one technology that is highly prevalent in modern society—the automatic teller machine (ATM). The findings indicated that users and nonusers differed in mechanical reasoning skills and in attitudes toward ATM technology. Older adults with higher mechanical reasoning skills were more likely to be ATM users. Nonusers had more negative attitudes toward ATMs, and, among non-users, those who had tried an ATM had more positive attitudes than those who had never tried one. The findings of this study are discussed in terms of factors that may affect the adoption of other technologies by older adults. Suggestions for increasing the acceptance of technologies by the elderly are also addressed.     

Relative Phase Alterations during Bimanual Skill Acquisition

The purposes of the research reported here were (a) to examine changes in relative phase during the acquisition of a new coordination pattern and (b) to determine the effect of learning this pattern on the ability to perform other coordination patterns. Ten subjects practiced an upper limb coordination task that required a 90° phase offset and different amplitudes for each arm. A gross approximation of the mean relative phase for the intended coordination pattern occurred quickly, but the attainment of stability occurred much more gradually. These results were accompanied by changes in pattern stability across practice and on various transfer tests. Learning of the new coordination pattern also affected the stability of the anti-phase mode, but this effect was only temporary.     

Perception—Action Coupling during Bimanual Coordination: The Role of Visual Perception in the Coalition of Constraints That Govern Bimanual Action

Constraints pertaining to interlimb coordination have been studied extensively in the past decades. In this debate, F. Mechsner (2004) has taken a provocative position by putting primary emphasis on perceptual principles that mediate coordinative stability. Whereas the present authors agree that the role of perceptual principles is of critical importance during coordination, they take issue with Mechsner's extreme position and with the evidence forwarded to support a purely perceptual-cognitive approach to bimanual coordination. More specifically, the authors emphasize that current knowledge about brain function argues against a dualism between perception and action, criticize the presented evidence that posture manipulations during coordination provide decisive evidence against motoric and muscular constraints, and report on potential pitfalls associated with the use of visual transformation procedures to support complex coordination patterns.