The utilization of visual feedback information during rapid pointing movements

Three experiments were conducted to determine how variables other than movement time influence the speed of visual feedback utilization in a target-pointing task. In Experiment 1, subjects moved a stylus to a target 20 cm away with movement times of approximately 225 msec. Visual feedback was manipulated by leaving the room lights on over the whole course of the movement or extinguishing the lights upon movement initiation, while prior knowledge about feedback availability was manipulated by blocking or randomizing feedback. Subjects exhibited less radial error in the lights-on/blocked condition than in the other three conditions. In Experiment 2, when subjects were forced to use vision by a laterally displacing prism, it was found that they benefited from the presence of visual feedback regardless of feedback uncertainty even when moving very rapidly (e.g. less than 190 msec). In Experiment 3, subjects pointed with and without a prism over a wide variety of movement times. Subjects benefited from vision much earlier in the prism condition. Subjects seem able to use vision rapidly to modify aiming movements but may do so only when the visual information is predictably available and/or yields an error large enough to detect early enough to correct.     

Optimizing the Use of Vision in Manual Aiming: The Role of Practice

The purpose of this study was to determine how subjects learn to adjust the characteristics of their manual aiming movements in order to make optimal use of the visual information and reduce movement error. Subjects practised aiming (120 trials) with visual information available for either 400 msec or 600 msec. Following acquisition, they were transferred to conditions in which visual information was available for either more or less time. Over acquisition, subjects appeared to reduce target-aiming error by moving to the target area more quickly in order to make greater use of vision when in the vicinity of the target. With practice, there was also a reduction in the number of modifications in the movement. After transfer, both performance and kinematic data indicated that the time for which visual information was available was a more important predictor of aiming error than the similarity between training and transfer conditions. These findings are not consistent with a strong “specificity of learning” position. They also suggest that, if some sort of general representation or motor programme develops with practice, that representation includes rules or procedures for the utilization of visual feedback to allow for the on-line adjustment of the goal-directed movement.     

Problem Solving,Stress, and Coping in Adolescent Suicide Attempts

Twenty adolescents who had made suicide attempts were compared with 20 nonpsychiatric control subjects on measures of problem solving, stress, and coping. The suicidal group did not show evidence of “rigid” thinking or of deficits in the ability to generate solutions to standardized interpersonal problems. However, they did report recent histories of more severe life stress and had inaccurate appraisal of the extent to which stressful events could be controlled. Although suicidal patients were able to generate as many adaptive strategies as control subjects for coping with their own most severe recent real-life stressor, they actually used fewer. They were also more likely to identify maladaptive behaviors as ways of coping. These findings support a transactional model of adolescent suicidal behavior, whereby inaccuracies in the appraisal aspects of problem solving (but not in the solution-generation aspects) in the face of high life stress lead to a reduction in the use of adaptive efforts to cope.