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Hiroshi Ueda, Kohske Takahashi, Katsumi Watanabe; The gap effect is predominantly determined by the awareness of the fixation disappearance. Journal of Vision 2013;13(9):1221. doi: https://doi.org/10.1167/13.9.1221.
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© ARVO (1962-2015); The Authors (2016-present)
Saccadic or manual reaction to a peripherally presented target is facilitated by the removal of a central fixation stimulus shortly before the onset of the target, compared to when the fixation stimulus remains (gap effect). The present study examined whether the perceptual disappearance of a fixation point is sufficient to induce the gap effect. Observers performed a reaction task in which they were required to fixate a central fixation point and make a saccade to the peripherally presented target (either the right or left of the fixation point) as quickly and accurately as possible. To discriminate the effects of perceptual and physical disappearance of a fixation point, we employed a consciously invisible fixation point that was suppressed by using binocular rivalry and continuous flash suppression technique. In a trial, a fixation point was presented to both dominant and suppressed eyes. Then, the fixation point was either (1) remained in both eyes, (2) remained in the suppressed eye while removed from the dominant eye, (3) removed from the suppressed eye while remained in the dominant eye, (4) removed from both eyes. A control experiment confirmed that observers were not aware of the existence, and hence disappearance, of the fixation point to the suppressed eye. The result shows that there was a significant main effect of the removal of a fixation point from the dominant eye, which leads to the gap effect. On the other hand, no such an effect was found by the removal from the suppressed eye, although a small simple effect was found when the fixation was removed from the dominant eye. Taken together, irrespective of the physical existence or disappearance of unnoticeable fixation point, the gap effect was mainly determined by the disappearance of the consciously visible fixation point.
Meeting abstract presented at VSS 2013
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