Continuous visual control of interception

People generally try to keep their eyes on a moving target that they intend to catch or hit. In the present study we first examined how important it is to do so. We did this by designing two interception tasks that promote different eye movements. In both tasks it was important to be accurate relative to both the moving target and the static environment. We found that performance was more variable in relation to the structure that was not fixated. This suggests that the resolution of visual information that is gathered during the movement is important for continuously improving predictions about critical aspects of the task, such as anticipating where the target will be at some time in the future. If so, variability in performance should increase if the target briefly disappears from view just before being hit, even if the target moves completely predictably. We demonstrate that it does, indicating that new visual information is used to improve precision throughout the movement.     

Judgments of reachability are independent of visuomotor adaptation

The furthest distance that is judged to be reachable can change after participants have used a tool or if they are led to misjudge the position of their hand. Here we investigated how judged reachability changed when visual feedback about the hand was shifted. We hoped to distinguish between various ways in which visuomotor adaptation could influence judged reachability. Participants had to judge whether they could reach a virtual cube without actually doing so. They indicated whether they could reach this virtual cube by moving their hand. During these hand movements, visual feedback about the position of the hand was shifted in depth, either away from or toward the participant. Participants always adapted to the shifted feedback. In a session in which the hand movements in the presence of visual feedback were mainly in depth, perceived reachability shifted in accordance with the feedback (more distant cubes were judged to be reachable when feedback was shifted further away). In a second session in which the hand movements in the presence of visual feedback were mainly sideways, for some participants perceived reachability shifted in the opposite direction than we expected. The shift in perceived reachability was not correlated with the adaptation to the shift in visual feedback. We conclude that reachability judgments are not directly related to visuomotor adaptation.     

Timing the moment of impact in fast human movements

The reported resolution of timing the moment of impact in fast human movements differs widely depending on the task. Surprisingly, better timing is reported for the demanding task of batting a ball than for the much simpler task of tapping in synchrony with two hands. We wondered whether this is because a sizeable part of timing variability arises from misjudging the distance in the direction of one's own movement, so that moving faster (as the bat does when moving toward a ball) improves timing. We found that moving faster does indeed improve timing in both the above-mentioned tasks. After removing the proposed contribution of misjudging the distance in the direction of one's own movement, we estimated that the remaining standard deviation in timing is just over 6ms for both tasks.     

Self-Report Measures to Identify Post Traumatic Stress Disorder and/or Mild Traumatic Brain Injury and Associated Symptoms in Military Veterans of Operation Enduring Freedom (OEF)/Operation Iraqi Freedom (OIF)

Individuals serving in Iraq and Afghanistan sustain injuries associated with physical and psychological trauma. Among such injuries, mild traumatic brain injury (mTBI) and post traumatic stress disorder (PTSD) are common. Self-report measures are frequently used to identify mTBI and/or PTSD and symptoms associated with these conditions. In addition to providing information regarding mTBI and PTSD, the goal of this literature review was to identify and present information on the psychometric properties of measures used to obtain information regarding these common conditions among Veterans who have returned from Operation Enduring Freedom (OEF)/Operation Iraqi Freedom (OIF). A comprehensive review of studies in which self-report measures were used to evaluate mTBI, PTSD, and associated symptoms among OEF/OIF Veterans is presented. Findings suggest that additional work is needed to identify psychometrically sound and clinically useful self-report measures that assess mTBI and PTSD and associated symptoms among OEF/OIF Veterans.     

The role of uncertainty in the systematic spatial mislocalization of moving objects

It only makes sense to talk about the position of a moving object if one specifies the time at which its position is of interest. The authors here show that when a flash or tone specifies the moment of interest, subjects estimate the moving object to be closer to where it passes the fixation point and further in its direction of motion than it really is. The authors propose that these biases arise from a combination of a large temporal uncertainty, a temporal asymmetry related to sampling the moving object's position, and a bias toward believing that one is looking at what one sees.     

Item Variances and Median Splits: Some Discouraging and Disquieting Findings

ABSTRACT In his response to our article, Baumeister argued that in real data, the confound between interitem variance and trait extremity is small (typically in the range of 0 and –.2), and that the danger of artifact associated with the application of median splits to interitem variance is not as serious as our first simulation study would lead one to believe. When we examined a large body of actual personality data, employing personality scales of average reliability and relatively large samples, we found that the average magnitude of the confound was –.15. However, we also found that even a confound as small as –.03 could be associated with significant differential range restriction of the trait scores within subsamples produced by the median split (MS) technique. We note that several factors, not just the magnitude of the interitem variance/trait extremity confound, must be considered when assessing the danger of artifact associated with the MS technique. We again conclude that researchers should use the moderated multiple regression (MMR) technique in preference to the MS technique when testing for moderating effects in personality research.     

Development and validation of the Illness Behavior Inventory

The development and validation of a measure of illness behavior are presented. From a large domain sample of illness-related behaviors, a 20-item self-report measure was developed, the Illness Behavior Inventory (IBI). Validation data are presented from a series of independent studies with healthy and chronically ill individuals. Results indicate that the IBI possesses acceptable levels of internal consistency, test-retest reliability, structural reliability, discriminant validity, concurrent validity, and predictive validity. The applicability of the IBI to various areas of inquiry in behavioral medicine research and practice is discussed and directions for future research are outlined.