Effects of moment of inertia on simple reaction time

Two experiments examined the effect of altering the moment of inertia within an anatomical unit on simple reaction time (SRT), premotor time (PMT), and motor time (MOT) during the initiation of a discrete rapid movement. In Experiment 1 (N = 14), moment of inertia of the forearm was increased with the addition of a weighted cuff fastened around the wrist. In Experiment 2 (N = 7), moment of inertia was altered by the addition of a weighted sleeve to the index finger prior to rapid extension of the digit. Results from both experiments were unequivocal. An increase in the moment of inertia resulted in a significant increase in SRT and MOT but had no significant effect on PMT. Within selected anatomical unites (forearm and index finger), an increase in the moment of inertia does not appear to require additional neuromotor programming time but does influence the overall duration of response initiation.     

Social-evaluative versus self-evaluative appearance concerns in Body Dysmorphic Disorder

Body Dysmorphic Disorder (BDD) is characterised by significant preoccupation and distress relating to an imagined or slight defect in appearance. Individuals with BDD frequently report marked concerns relating to perceived negative evaluation of their appearance by others, but research specifically investigating such concerns remains limited. This study investigated the extent and nature of appearance-related social-evaluative and self-evaluative concerns in individuals with BDD and healthy controls. BDD participants, in comparison to controls, reported high levels of importance and anxiety associated with perceptions of others' views of their appearance, in addition to their own view. No differences were observed in the level of importance and anxiety associated with their self-view in comparison to others' views. These findings support existing evidence indicating that appearance-related social-evaluative concerns are a central feature of BDD. Cognitive-behavioural treatment implications are discussed.     

Brain activity related to the ability to inhibit previous task sets: an fMRI study

Switching between tasks requires individuals to inhibit mental representations of the previous task demands and to activate representations of the new demands. To date, investigators have identified only one way to measure task set inhibition??that is, through a backward inhibition (BI) paradigm. In this paradigm, participants take more time to return to a task set that was recently abandoned (e.g., ??A?? in an ABA task sequence) than to a nonrecently abandoned task set (e.g., CBA), and investigators have demonstrated that this time cost reflects time needed to overcome the inhibition of the recently abandoned task set. To date, however, investigators have not been able to use this paradigm, or any other, to isolate brain activity related to task set inhibition. For example, contrasting the brain activity elicited by ABA and CBA trials will not isolate activity related to task set inhibition, because inhibition occurs during the initial switch away from task A (i.e., ABA). Given that there is currently no way to directly isolate the brain activity related to task set inhibition, we decided instead to examine how brain activity during task switching varies in individuals who are better than others at inhibiting the previous task set. We found that participants who were good at inhibiting previous task sets, as measured with the BI paradigm, exhibited more activity in the basal ganglia and supplementary motor area/premotor area when task switching, as measured via functional magnetic resonance imaging. These findings suggest that activity in these regions plays a role in task set inhibition.     

Cortical Cell Assemblies: A Possible Mechanism for Motor Programs

The concept of a motor program has been used to interpret a diverse range of empirical findings related to preparation and initiation of voluntary movement. In the absence of an underlying mechanism, its explanatory power has been limited to that of an analogy with running a stored computer program. We argue that the theory of cortical cell assemblies suggests a possible neural mechanism for motor programming. According to this view, a motor program may be conceptualized as a cell assembly, which is stored in the form of strengthened synaptic connections between cortical pyramidal neurons. These connections determine which combinations of corticospinal neurons are activated when the cell assembly is ignited. The dynamics of cell assembly ignition are considered in relation to the problem of serial order. These considerations lead to a plausible neural mechanism for the programming of movements and movement sequences that is compatible with the effects of precue information and sequence length on reaction times. Anatomical and physiological guidelines for future quantitative models of cortical cell assemblies are suggested. By taking into account the parallel, re-entrant loops between the cerebral cortex and basal ganglia, the theory of cortical cell assemblies suggests a mechanism for motor plans that involve longer sequences. The suggested model is compared with other existing neural network models for motor programming.     

In the Blink of an I: On Delayed but Identical Subjective Reactions and Their Effect on Self-Interested Behavior

People believe that they have shared an identical subjective experience—that they have I-shared—when they react identically and simultaneously to the same stimulus. Despite growing evidence for I-sharing, researchers have yet to ask whether simultaneity really makes a difference. We test the importance of simultaneity for I-sharing effects. Participants played prisoner’s dilemma with someone who shared their subjective self, their objective self, or neither. Some participants learned this information immediately; others, after a short delay. Time delay decreased cooperation in the subjective similarity condition, but not in the objective similarity or neither conditions. These findings underscore the importance of simultaneity for I-sharing effects and highlight the implications of I-sharing for cooperation and self-interested behavior.     

Accuracy of retrospective memory and covariation estimation in patients with obsessive-compulsive disorder

Assessment methods relying on biased or inaccurate retrospective recall may distort knowledge about the nature of disorders and lead to faulty clinical inferences. Despite concerns about the accuracy of retrospective recall in general and in particular with obsessive–compulsive disorder (OCD) patients, the accuracy of retrospective recall for one's own symptoms assessed in vivo is unknown in this population. This study used a prospective ecological momentary assessment (EMA) methodology to create a criterion against which to assess recall accuracy in OCD patients. Although results indicated that patients’ retrospective recall of OCD symptoms was fairly accurate, they consistently overestimated the magnitude of OCD symptom covariation with non-OCD facets (e.g., sleep duration, contemporaneous stress level, etc.). Findings suggest that even when recall of OCD symptoms is accurate, patients may be inaccurate in estimating symptom covariation. The findings have implications for the research, case conceptualization, and assessment of OCD, and may extend to other disorders.     

Partisanship,Political Knowledge,and the Dunning‐Kruger Effect

A widely cited finding in social psychology holds that individuals with low levels of competence will judge themselves to be higher achieving than they really are. In the present study, I examine how the so‐called “Dunning‐Kruger effect” conditions citizens' perceptions of political knowledgeability. While low performers on a political knowledge task are expected to engage in overconfident self‐placement and self‐assessment when reflecting on their performance, I also expect the increased salience of partisan identities to exacerbate this phenomenon due to the effects of directional motivated reasoning. Survey experimental results confirm the Dunning‐Kruger effect in the realm of political knowledge. They also show that individuals with moderately low political expertise rate themselves as increasingly politically knowledgeable when partisan identities are made salient. This below‐average group is also likely to rely on partisan source cues to evaluate the political knowledge of peers. In a concluding section, I comment on the meaning of these findings for contemporary debates about rational ignorance, motivated reasoning, and political polarization.     

Interactions among end-effectors and movement parameters influence reaction time in discrete, rapid aimed movements.

Two reliable findings in discrete, rapid aimed movements are that reaction time increases with decrease in target diameter (for the short-length movements), and reaction time is not affected by movement length [Journal of Experimental Psychology, Human Perception and Performance 104 (2) (1975) 147]. Participants normally use a short stylus (SS) to tap targets located on either side of a central (aligned with body midline) start-point with no restrictions imposed on the initial posture of the limb or segmental recruitment except as determined by movement conditions. Thus, the effects of movement parameters on reaction time in previous work are potentially confounded with the effect of initial posture of the limb at the start-point, along with order and amount of the contribution of segments recruited in response execution. Two experiments were performed to resolve the confounding between initial posture and recruitment of limb segments. In the first experiment a conventional stylus (pen-like) was employed and the starting position of the limb was aligned either with the body midline or with the participant's right shoulder. The effect of starting position on reaction time was not significant. In the second experiment the starting position was in line with the right shoulder. Two groups participated. One group used a conventional stylus. For the second group a modified (lengthened) stylus was used that permitted initial limb posture and number of limb segments recruited to be held constant across an extended range of movement lengths. When similar sets of limb segments were used, reaction time increased with decreasing movement length and diminishing target diameter. These findings suggest that uncontrolled initial limb posture, uncontrolled order of joint(s) recruitment, and the subsequent inclusion of reaction time values from incompatible sources may, in the final analysis, have confounded previous work investigating movement amplitude and target diameter effects on reaction time.     

The influence of advance information about target location and visual feedback on movement planning and execution.

This study was designed to determine if movement planning strategies incorporating the use of visual feedback during manual aiming are specific to individual movements. Advance information about target location and visual context was manipulated using precues. Participants exhibited a shorter reaction time and a longer movement time when they were certain of the target location and that vision would be available. The longer movement time was associated with greater time after peak velocity. Under conditions of uncertainty, participants prepared for the worst-case scenario. That is, they spent more time organizing their movements and produced trajectories that would be expected from greater open-loop control. Our results are consistent with hierarchical movement planning in which knowledge of the movement goal is an essential ingredient of visual feedback utilization.     

Depressive rumination and the C957T polymorphism of the DRD2 gene

Depressed individuals who ruminate have difficulties learning from punishment and suppressing task-irrelevant information. The C957T polymorphism of the DRD2 gene, which affects functioning of D2 dopamine receptors (DRD2) that are expressed predominantly in the indirect pathway of the basal ganglia, has been found to influence suppression and punishment learning. Given these associations, we examined in the present study whether depressive rumination is related to the C957T polymorphism in 317 clinically depressed individuals and 317 never-depressed control individuals. A 2 × 2 (diagnostic group ×C957T polymorphism) analysis of variance conducted on depressive rumination scores yielded a significant interaction of group and C957T: Individuals with two 957C alleles reported higher levels of depressive rumination than did individuals with one or two 957T alleles if they were depressed, but not if they were healthy. The present findings suggest that the dopaminergic system and DRD2 are related to the frequency of maladaptive rumination in depressed individuals. Thus, DRD2 may be an important target for the pharmacological treatment of depressive rumination.