“School of Cognitive Sciences”
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| Paper IPM / Cognitive Sciences / 8973 |
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| Abstract: | |||||
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We used a spatiotemporal weighted averaging model of motion perception in
which the perception attributed to the position of a moving object at time t is
a function of its positions in a time interval [t - a, t +b ]. To determine the
model parameters, we designed a motion reversal paradigm in which two bars
at the opposite sides of the screen moved towards each other, and when they
met the direction of their motion reversed. The subjects perceived that the
motion reversal occured before the stimuli reached each other. To determine
the effect of flashing stimuli, two flashes appeared at the time of motion
reversal. The dependence of the perceived misalignment between flashes
and the moving stimuli on both pre- and post-flash speed of the moving stimuli
indicates that motion perception system is neither predictive as proposed by
Nijhawan (1994 Nature 370 256-257), nor postdictive as proposed by
Eagleman and Sejnowski (2000 Science 287 2036 - 2038), but it uses a time
window of 160 ms to calculate the position of moving objects at a time within
this interval. Comparison of the results indicates that the flash has no
significant effect on both the limits of the time window of integration and the
weights [Supported by the School of Cognitive Sciences, Institute for
Research in Fundamental Sciences, Tehran, the Laboratories for Brain and
Cognitive Sciences, Shaheed Beheshti University of Medical Sciences,
Tehran, and the Iran University of Science and Technology, Tehran.]
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