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AJ Reeves; The Anti-Saccade . Invest. Ophthalmol. Vis. Sci. 2002;43(13):2875.
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Purpose: To describe visual function when an eye movement in one direction occurs at the same time as a shift of attention in the opposite direction. Methods: Four subjects were trained to saccade from left to right while simultaneously shifting attention the same way ('pro-shifting') or from right to left ('anti-shifting'). Subjects viewed a display screen with two RSVP streams, one of single letters (located 1.8 deg left of a central dot) and the other of single numerals (located 1.8 deg to the right). Characters were 1.5 deg high, 1.2 deg wide, large enough to be identifiable in the parafovea. In pro-shifting, subjects fixated and attended to the letter stream, then, on noting a target letter, moved both eyes and attention to the numeral stream. In anti-shifting, subjects fixated the numeral stream while attending to the letters, and then, after noting the target, moved attention to the numerals and eyes to the letters. Now attending to the numerals, the subject reports the first four he can. The latency of the attention shift is defined as the time from target letter onset to onset of the first reported numeral (the 'attention shift paradigm' of Reeves and Sperling, Psychological Review 93, 1986, 180-206.) Letters and numerals were presented rapidly enough (10 Hz) so verbalizing each item as it was shown was impossible (so reports are from visual memory), but not so rapidly that items were guessed. Results: Pro-shifting is an everyday looking behavior, but it takes several hours of practice to proficiently anti-shift. Our well-practiced subjects' eye movements become automated: the eye tracker shows almost the same latency (and precision within a 0.9 deg window) for anto- as for pro-shifting. The well-practiced attention shift latencies were only slightly slower (<30 msec) for an anti- as a pro-shift. Generalizing to new screen locations is rapid. Conclusion: Eye and attention movements are not inevitably yoked together. Such a yoke can be broken with practice.
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