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Ljubica Jovanovic, Pascal Mamassian; When a visual event is perceived depends on where it is presented. Journal of Vision 2018;18(10):714. doi: https://doi.org/10.1167/18.10.714.
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Perceiving when an event occurs is important to properly act on it. The speed of visual processing increases with stimulus eccentricity (Carrasco et al., 2003), and perceived duration of visual events is contracted in the periphery (Aedo-Jury & Pins, 2010). Here, we investigated whether when an event is perceived depends on eccentricity. Participants were initially familiarized with a fixed interval duration by watching the hand of a clock rotating at a constant speed, making one full revolution in 2 seconds. In the main part of the experiment, the hand was removed and a small disc was briefly flashed at a random time within the interval duration. Participants used a cursor to indicate the location where the hand would have been at the time of the flash. In different blocks of trials, the discs were presented at different eccentricities from 0° to 36° (in 5 logarithmically equally spaced steps). To minimize attentional redirection to one hemifield, two stimuli were simultaneously presented on either side of fixation. The outline of the clock was either presented or omitted during the familiarisation and test phases. In a subsequent experiment, stimulus size was scaled according to a cortical magnification factor (Duncan & Boynton, 2003). Events were perceived earlier when they were presented in the periphery rather than at fixation. A bias of around 100 msec was present for stimuli close to the location of the response probe (the outline of the clock and the tip of its hand). In addition, there was also a smaller bias to report events earlier for larger eccentricities. Scaling the size of the stimuli did not reduce the biases. In summary, perceiving when an event occurs depends on how far it is in the periphery and where it is relative to objects we intend to act on.
Meeting abstract presented at VSS 2018
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