The effect of orientation-related prior probability information on contrast perception

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.