The effect of orientation-related prior probability information on contrast perception
Author
Nazlı, İlayda
Advisor
Boyacı, Hüseyin
Date
2019-07Publisher
Bilkent University
Language
English
Type
ThesisItem Usage Stats
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Abstract
It is known that visual perception is the product of sensory input and prior probability
information. Previous studies support well that expectation influence recognition
and decision-making; however, we have limited knowledge about how expectation influences
low level visual processing. In the current study, we examine the effect of
expectation on early visual processing. That is, we provide task-irrelevant expectation
cue related to the orientation of target Gabor grating, and we ask participants to
indicate the spatial location of target grating while systematically manipulating its
contrast level. In addition, we examine how different expectation validities (i.e. 75%,
50%, 100%) and neutral expectation cue affect visual perception. In Experiment 1,
where the orientation of expectation cue and target gratings are vertical or horizontal, contrast threshold is lower in congruent trials at 75% validity condition. In Experiment
2, where the orientation of cue grating implies specific range (i.e. ±15 around 0 or 90), contrast threshold is lower in congruent trials at 75% and 50%
validity condition. In Experiment 3B, where the orientation of expectation cue and target Gabor grating are within wider range (i.e. ±30 around 0 or 90), contrast
threshold is lower in congruent trials at 75% validity condition. In Experiment 3A, where the orientation
of expectation cue and target Gabor grating are within a specific range (i.e. ±15 around 0 or 90) contrast threshold is lower in congruent trials at 75% and 50%
validity condition. In Experiment 3B, where the orientation of expectation cue and target Gabor grating are within wider range (i.e. ±30 around 0 or 90), contrast
threshold is lower in congruent trials at 75% validity condition.