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Alexander C. Schütz; The influence of retinal and head-centered motion on perceived duration. Journal of Vision 2011;11(11):1224. doi: https://doi.org/10.1167/11.11.1224.
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© ARVO (1962-2015); The Authors (2016-present)
The apparent duration of moving stimuli increases with temporal frequency (Kanai et al., Journal of Vision, 2006) or speed (Kaneko & Murakami, Journal of Vision, 2009). Here we investigated if this increase depends on retinal or head-centered temporal frequency respective speed. Smooth pursuit eye movements were used to disentangle retinal from head-centered motion.
We presented two Gabors in separate time intervals and asked subjects to judge which one lasted longer. The Gabors had a sinusoid spatial frequency of 1 c/deg, a Gaussian standard deviation of 0.75 deg and were presented 4 deg above or below a fixation point. One Gabor had a fixed duration of 500 ms (standard) and was oriented vertically, so that its retinal speed was modulated by horizontal eye movements. The other Gabor had a variable duration (test) and was oriented horizontally, so that its retinal speed was independent of horizontal eye movements. The order of standard and test was randomized. In a fixation baseline condition the fixation point was stationary and the standard Gabor was drifting inside the stationary envelope at speeds of 3.5, 7.0, 10.5 and 14.0 deg/s. In two different pursuit conditions the fixation point moved horizontally at the same speeds: In a retinal motion condition, the standard sinusoid was physically stationary but moving on the retina. In a head-centered motion condition the standard sinusoid drifted at the same speed as the fixation point, so that it was stabilized on the retina.
The apparent duration increased with speed in the fixation baseline condition. In the retinal motion condition, the increase of apparent duration was similar to the fixation baseline condition. However there was almost no increase of apparent duration with speed in the head-centered motion condition. These results suggest that perceived duration depends on retinal rather than on head-centered motion.
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