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E. Morya, G. Savelsbergh, F. Ferlazzo, R. Ranvaud; Involuntary Eye Movements and Attentional Shifts in a Time–to–Contact Task . Invest. Ophthalmol. Vis. Sci. 2005;46(13):5655.
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Purpose: Study shifts in visual attention by measuring eye movements of volunteers in a time–to–contact task. Methods: Volunteers (18) had to tilt a lever at the exact moment a moving spot overlapped a stationary spot on the computer screen, and, if at all possible, in the direction indicated by a third spot. The third spot started moving right or left (indicating which way the lever should be tilted) at random intervals (50–1071 ms) before the superposition of the two other spots. Results: If left free to look wherever they wished, volunteers tended to fix alternatively the moving spot and the stationary spot, but invariably ended up looked at the stationary spot at the time of overlap – and shortly before. When asked to do so, volunteers were able to their gaze fixed on the stationary spot throughout each test. However, if asked to follow the moving spot with their gaze, unconsciously they switched to the stationary spot at least 500 ms before contact. This is much longer than the 350–400 ms required for the volunteers to respond to the indication of the third spot with 100% reliability. If the motion of the third spot occurred at the moment of the switch to fixating the stationary spot (when asked to fix the moving spot), or the time of a proposed covert attentional shift (when fixing the stationary spot), there was a strong tendency to slightly (10–12 ms), but significantly, anticipate responses. Conclusions: Overall these data are suggestive of an automatic shift of visual attention to the stationary spot at least 500 ms prior to the time of contact, when executing the time–to–contact task. Anticipations when the indication of direction occurs at this time might be the result of several possibilities, such as interference between preparatory pre–motor processes, or even distortions in time perception associated with the shift in visual attention.
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