The Effect of Complex Motion Pattern on Speed Perception
Bard J. Geesaman and Ning Qian, Vision Research, 1998,
38:1223-1231.
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Abstract
We recently reported a new motion illusion where dots in expanding
random dot patterns appear to move faster than those in rotation
patterns despite having the same physical speed distributions
(Geesaman & Qian, 1996). In the current paper, we compared expansion
and rotation motion to translational motion and found that the
perceived dot speed in translation patterns was between that of
expansion and rotation. We also explored contraction motion and found
subjects perceived dots in contracting patterns as moving slightly
faster than those in expanding patterns and much faster than those in
rotating patterns. Finally, we found that stimulus presentation order
in a trial plays an important role in determining the magnitude of the
speed illusion - the effect is greater when the subjectively faster
stimulus is viewed second (e.g. expansion after rotation). The
dependence on stimulus order is greatest when comparing complex motion
patterns with large subjective speed differences. This phenomenon is
unlikely to be explained in terms of channel fatigue or adaptation.
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