Article

Continuous visual control of interception

Research Institute MOVE, Faculty of Human Movement Sciences, VU University Amsterdam, Van der Boechorststraat 9, NL-1081 BT Amsterdam, The Netherlands.
Human movement science (Impact Factor: 2.03). 02/2011; 30(3):475-94. DOI: 10.1016/j.humov.2010.12.007
Source: PubMed

ABSTRACT 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.

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    • "The target moved for considerably longer than 116 ms, but assuming that the tapping movement is continuously adjusted (Brenner & Smeets, 2011), we would only expect to see effects of anything that is ignored during the final part of the movement, when sensorimotor delays prevent direct feedback-based correction. A sensorimotor delay of about 116 ms is reasonably consistent with the literature (Brenner & Smeets, 1997; Carlton, 1981; Oostwoud Wijdenes et al., 2011). "
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    ABSTRACT: People can hit rapidly moving balls with amazing precision. To determine how they manage to do so, we explored how various factors that we could manipulate influenced people's precision when intercepting virtual targets. We found that temporal precision was highest for fast targets that subjects were free to intercept wherever they wished. Temporal precision was much poorer when the point of interception was specified in advance. Examining responses to abrupt perturbations of the target's motion revealed that people adjusted where rather than when they would hit the target if given the choice. A model that combines judging how long it will take to reach the target's path with estimating the target's position at that time from its visually perceived position and velocity could account for the observed precision with reasonable values for all the parameters. The model considers all relevant sources of errors, together with the delays with which the various aspects can be adjusted. Our analysis provides a biologically plausible explanation for how light falling on the eye can guide the hand to intercept a moving ball with such high precision. © 2015 ARVO.
    Journal of Vision 03/2015; 15(3). DOI:10.1167/15.3.8 · 2.73 Impact Factor
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    • "Experimental evidence of visual control in the course of action has shown for arm and hand movements (e.g. grasping a static target (Goodale, 2011); intercepting a moving target (Brenner & Smeets, 2011)), as well as driving (Wallis et al., 2007). "
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    ABSTRACT: An experiment was conducted in a driving simulator to test how eye-movement patterns evolve over time according to the decision-making processes involved in a driving task. Participants had to drive up to a crossroads and decide to stop or not. The decision-making task was considered as the succession of two phases associated with cognitive processes: Differentiation (leading to a prior decision) and Consolidation (leading to a final decision). Road signs (Stop, Priority and GiveWay) varied across situations, and the stopping behavior (Go and NoGo) was recorded. Saccade amplitudes and fixation durations were analyzed. Specific patterns were found for each condition in accordance with the associated processes: high visual exploration (larger saccade amplitudes and shorter fixation durations) for the Differentiation phase, and lower visual exploration (smaller saccades and longer fixations) for the Consolidation phase. These results support that eye-movements can provide good indexes of underlying processes occurring during a decision-making task in an everyday context.
    Journal of Eye Movement Research 08/2014; 7(4):1-14. · 1.06 Impact Factor
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    • "However, in Experiment 3, subjects were more precise when the ball was visible for about 970 ms than when it was visible for about 450 ms, suggesting that it is advantageous to see the ball for some time before initiating the forward movement of the bat. The results of Experiment 4 show that seeing the ball earlier, and therefore having more information with which to select the optimal moment to initiate the swing, is less important than seeing the ball throughout the bat's movement, probably because subjects adjust their bat's motion to that of the ball throughout the movement (Bootsma and van Wieringen, 1990; Peper et al., 1994; Caljouw et al., 2004; Brenner and Smeets, 2011). Taken together, the results of our four experiments suggest that people primarily time their hits so precisely by using the perceived changing elevation of the ball throughout the swing to adjust the bat's movement to that of the ball. "
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    ABSTRACT: People are extremely good at hitting falling balls with a baseball bat. Despite the ball's constant acceleration, they have been reported to time hits with a standard deviation of only about 7 ms. To examine how people achieve such precision, we compared performance when there were no added restrictions, with performance when looking with one eye, when vision was blurred, and when various parts of the ball's trajectory were hidden from view. We also examined how the size of the ball and varying the height from which it was dropped influenced temporal precision. Temporal precision did not become worse when vision was blurred, when the ball was smaller, or when balls falling from different heights were randomly interleaved. The disadvantage of closing one eye did not exceed expectations from removing one of two independent estimates. Precision was higher for slower balls, but only if the ball being slower meant that one saw it longer before the hit. It was particularly important to see the ball while swinging the bat. Together, these findings suggest that people time their hits so precisely by using the changing elevation throughout the swing to adjust the bat's movement to that of the ball.
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