The influence of a secondary task and type of feedback on adaptation to lateral displacement of the visual array

Summary This experiment was designed to investigate the influence of a secondary attention-demanding force-production task on adaptation to prismatic displacement. Recent suggestions by Finke (1979) lead to the prediction that a secondary task executed during adaptation would interfere with the central component of adaptation (as measured by intermanual transfer), but not the peripheral component (adaptation specific to adapted limb). There were three secondary task conditions (no task, easy task, difficult task). Other factors investigated were: type of feedback (continuous, terminal), hand adapted (right, left) and prism orientation (base right, base left). While negative aftereffect was not influenced by the secondary task manipulation, intermanual transfer results provide partial support for Finke's model. Correlational analyses indicate the importance of task-specific parameters in determining the nature of perceptual-motor adaptation.     

Intermittent vision and one-handed catching: the effect of general and specific task experience

In Experiment 1, 15 skilled and 15 less skilled participants performed 1-handed catching in 4 conditions. For both groups, catching performance deteriorated significantly when no visual information was available for 40 ms between 20-ms visual samples (20/40) and continued to decline with subsequent increases in the duration between visual samples (i.e., 20/80 and 20/120). In Experiment 2, 50 participants performed a pretest and a posttest in a 20/80 condition, separated by 4 blocks of practice (N=80). Participants who practiced with intermittent vision (20/40, 20/80, and 20/120) exhibited a significant improvement between pretest and posttest. Although general practice with intermittent vision enabled some adaptation, posttest performance did not equal performance in the 1st block of continuous vision.     

Visual illusions affect both movement planning and on-line control: a multiple cue position on bias and goal-directed action

Over the last decade, there has been an interest in the impact of visual illusions on the control of action. Much of this work has been motivated by Milner and Goodale's two visual system model of visual processing. This model is based on a hypothesized dissociation between cognitive judgments and the visual control of action. It holds that action is immune to the visual context that provides the basis for the illusion-induced bias associated with cognitive judgments. Recently, Glover has challenged this position and has suggested that movement planning, but not movement execution is susceptible to visual illusions. Research from our lab is inconsistent with both models of visual-motor processing. With respect to the planning and control model, kinematic evidence shows that the impact of an illusion on manual aiming increases as the limb approaches the target. For the Ebbinghaus illusion, this involved a decrease in the time after peak velocity to accommodate the 'perceived' size of the target. For the Müller-Lyer illusion, the influence of the figure's tails increased from peak velocity to the end of the movement. Although our findings contradict a strong version of the two visual systems hypothesis, we did find dissociations between perception and action in another experiment. In this Müller-Lyer study, perceptual decisions were influenced by misjudgment of extent, while action was influenced by misjudgment of target position. Overall, our findings are consistent with the idea that it is often necessary to use visual context to make adjustments to ongoing movements.     

Self-selected visual information during discrete manual aiming

The authors examined strategic selection of visual samples during manual aiming. Participants (N = 12) wore liquid-crystal goggles while performing discrete movements to a small target. Initially, participants controlled a 40-ms visual sample via a switch in their nonaiming hand. Subsequently, experimenter-imposed strategies required participants to take visual samples before movement initiation or early or late in the movement. Although participants adopted a variety of strategies to optimize the use of vision, they were more likely to select a sample during the early stages of the movement. Experimenter-imposed early and late instructions resulted in longer movement times than did self-selected sampling. Compared with late sampling, early sampling resulted in a temporal advantage with similar accuracy.     

Online versus offline processing of visual feedback in the control of movement amplitude

Researchers have suggested that visual feedback not only plays a role in the correction of errors during movement execution but that visual feedback from a completed movement is processed offline to improve programming on upcoming trials. In the present study, we examined the potential contribution of online and offline processing of visual feedback by analysing spatial variability at various kinematic landmarks in the limb trajectory (peak acceleration, peak velocity, peak negative acceleration and movement end). Participants performed a single degree of freedom video aiming task with and without vision of the cursor under four criterion movement times (225, 300, 375 and 450 ms). For movement times of 225 and 300 ms, the full vision condition was less variable than the no vision condition. However, the form of the variability profiles did not differ between visual conditions suggesting that the contribution of visual feedback was due to offline processes. In the 375 and 450 ms conditions, there was evidence for both online and offline control as the form of the variability profiles differed significantly between visual conditions.     

Integration of intermittent visual samples over time and between the eyes

The authors investigated the integration of alternate disparate monocular inputs for binocular perception in 1-handed catching experiments (N = 14, 32, 22, and 15 participants, respectively in Experiments 1-4). They varied the no-vision interval between alternate monocular samples to measure catching performance, and they compared the alternating monocular conditions with binocular and monocular conditions with equal no-vision intervals. They found no evidence of a binocular advantage for one-handed catching in the alternating monocular conditions. Performance in monocular and alternating monocular conditions did not differ across no-vision intervals ranging from 0-80 ms and was particularly worse than performance in binocular viewing conditions when the no-vision interval was 40 ms or more. The authors argue that the dissimilarity between disparate monocular inputs created by the approaching object limited the integration of those inputs and subsequent binocular perception.     

The Survey of European Psychotherapy Training 3: what psychotherapy is available in Europe?

Information provided in interview with key informantsin twenty-one European countries showed that there is a wide-range of different modalities of psychotherapy in Europe. Some are limited to their country of development but others are more wide-spread. Only four modalities are practised in the majority of countries. Psychodynamic (in every country), systemic family, gestalt.     

The Impact of Strategic Trajectory Optimization on Illusory Target Biases During Goal-Directed Aiming

During rapid aiming, movements are planned and executed to avoid worst-case outcomes that require time and energy to correct. As such, downward movements initially undershoot the target to avoid corrections against gravity. Illusory target context can also impact aiming bias. Here, the authors sought to determine how strategic biases mediate illusory biases. Participants aimed to Müller-Lyer figures in different directions (forward, backward, up, down). Downward biases emerged late in the movement and illusory biases emerged from peak velocity. The illusory effects were greater for downward movements at terminal endpoint. These results indicate that strategic biases interact with the limb-target control processes associated with illusory biases. Thus, multiple control processes during rapid aiming may combine and later affect endpoint accuracy (D. Elliott et al., 2010 Elliott, D., Hansen, S., Grierson, L. E. M., Lyons, J., Bennett, S. J., &; Hayes, S. J. (2010). Goal-directed aiming: two components but multiple processes. Psychological Bulletin, 136, 1023–1044.[Crossref], [PubMed], [Web of Science ®] , [Google Scholar]).