Limits of end-state planning

The end-state comfort effect is the tendency to use an uncomfortable initial grasp posture for object manipulation if this leads to a comfortable final posture. Many studies have replicated the end-state comfort effect across a range of tasks and conditions. However, these tasks had in common that they involved relatively simple movements, such as picking up a dowel or sliding a pan from one place to another. Here we asked whether the end-state comfort effect extends to more complex tasks. We asked participants to grasp a transparent bowl and move the bowl to an instructed location, positioning it in an instructed orientation. We either found an initial-state comfort effect or equal degrees of comfort for end-grasps and start-grasps depending on task instructions. The end-state comfort effect was not consistently observed. The results suggest that the end-state comfort effect may be restricted to relatively simple grasping movements.     

Peers influence adolescent reward processing,but not response inhibition

Most adolescent risk taking occurs in the presence of peers. Prior research suggests that peers alter adolescents’ decision making by increasing reward sensitivity and the engagement of regions involved in the processing of rewards, primarily the striatum. However, the potential influence of peers on the capacity for impulse control, and the associated recruitment of the brain’s control circuitry, has not yet been adequately examined. In the current study, adolescents underwent functional neuroimaging while they completed interleaved rounds of risk-taking and response-inhibition tasks. Social context was manipulated such that the participants believed they were either playing alone and unobserved, or watched by an anonymous peer. Compared to those who completed the tasks alone, adolescents in the peer condition took more risks during the risk-taking task and exhibited relatively heightened activation of the striatum. Activity within this striatal region also predicted individual differences in overall risk taking. In contrast, the presence of peers had no effect on behavioral response inhibition and had minimal impact on the engagement of typical cognitive control regions. In a subregion of the anterior insula engaged mutually by both tasks, activity was again found to be sensitive to social context during the risk-taking task, but not during the response-inhibition task. These findings extend the evidence that the presence of peers biases adolescents towards risk taking by increasing reward sensitivity rather than disrupting cognitive control.     

Preference for local or general anesthesia,coping dispositions,learned resourcefulness and coping with surgery

Abstract

People were found to differ in their coping dispositions (as measured with the MBSS, Miller, 1987): those who habitually attend to threatening cues (“monitors”) and those who distract themselves from these cues (“blunters”). However, some people are equally high on both coping dispositions and they were considered to be in a “dispositional conflict”. Furthermore, under certain circumstances people may prefer to act in a way that is inconsistent with their coping disposition; monitors who prefer blunting strategies and blunters who prefer monitoring strategies (labeled here as “disposition-behavior conflict”). Both conflicts were hypothesized to be associated with higher levels of trait anxiety and poorer coping. 59 men scheduled for surgery were assessed as to their coping disposition (monitors or blunters) and their preference for local or general anesthesia, and their learned resourcefulness (selfantrol skills). Monitors who chose general anesthesia (and thus were unable to monitor their own surgery) and blunters who chose local anesthesia (and thus were unable to blunt) were defined as being in a disposition-behavior conflict. Re- and post-surgery measures of anxiety and dysphoria and post-surgery nurses' ratings were used for assessing coping with surgery. Patients who were either high on dispositional conflict or showed a disposition-behavior conflict were higher on trait anxiety and showed poorer post-surgery coping in comparison to patients without such conflicts. Learned resourcefulness was not related to better coping nor to the two conflicts with the exception that patients with a disposition-behavior conflict reported less confidence in their self-control abilities. Overall, preference for local anesthesia predicted better post-surgery coping.     

Prospective and retrospective effects in human motor control: planning grasps for object rotation and translation

People pick up objects in ways that reflect prospective as well as retrospective control. Prospective control is indicated by planning for end-state comfort such that people grasp a cylinder to be rotated or translated with a hand orientation or at a height that affords a comfortable final posture. Retrospective control is indicated when people reuse a remembered grasp rather than using a new grasp that would ensure end-state comfort. Here, we asked whether these manifestations of prospective and retrospective control co-occur. We did so by having healthy young-adult participants grasp a cylinder to rotate and translate it between a horizontal position and a vertical position at each of five heights. We found that participants planned for comfortable final hand orientations for first moves but relied on recall for subsequent hand orientations. The results suggest that motor planning is sensitive to computational as well as physical demands and that object rotation and translation are not dissociable features of motor control, at least as reflected in their contributions to grasp selection. The latter result is consistent with the hypothesis that movements constitute holistic body changes between successive goal postures.     

Metacognitive control of action: Preparation for aiming reflects knowledge of Fitts’s law

Metacognitive control has been studied in intellectual skills but has not yet been studied in perceptual-motor skills. To probe metacognitive control in a perceptual-motor context, we developed a task in which participants chose the position of a cursor relative to two targets. One of the two targets was randomly erased. Participants tried to move the cursor into the remaining target within a limited amount of time. The target widths were varied, making the difficulty of moving to either target dependent on the chosen cursor position. Predictions were based on the assumption that participants could use an analogue of Fitts’s law to choose optimal positions. The fit between observed and predicted positions was excellent, suggesting that participants used information about movement speed-accuracy trade-offs to guide movement preparation. The findings suggest that metacognition applies to both perceptual-motor skills and intellectual skills, and that these two domains are more similar than traditionally assumed.