How Does Transient Attention Alter The Contrast Appearance?

A perennial question in the field of psychology is whether attention alters appearance.That is,whether attending to some part of our sensory experiences changes that experience.Recent studies have shown that an exogenous cue tends to increase the perceived contrast of a low-contrast stimulus.However,disputes remain as some other researchers argued that the observed effect was due to response bias,thus was not genuinely perceptual.In this thesis,we investigated the following questions with the methods of human behavioral psychophysics,combined with ERP technique and neural computational modeling:(1)Does transient attention alter contrast appearance?If so,how?(2)What are the temporal characteristics of the attentional modulation on contrast appearance?(3)Through what mechanism does attention modulate the contrast appearance?Through a series of three studies,we discovered that:(1)Attention does alter the contrast appearance.Particularly,the attentional effect depended on the simulation level of the stimulus.Directing attention to the location of a low-contrast stimulus would make the stimulus appear higher in contrast than it really was(enhancement effect),but directing attention to the location of a high-contrast stimulus would make the stimulus appear lower in contrast than it really was(attenuation effect).(2)The attentional effect on contrast appearance was short-lived,when it was induced by an exogenous cue.(3)The attentional effect on contrast appearance was associated with a two-stage cortical processing,including an enlarged neural response in an early time window together with a decreased neural response in a late time window.The results suggested that attention decreased the perceived contrast of high-contrast stimuli by boosting early sensory processing but suppressing late sensory processing.Besides,we found the attentional modulation on perceived contrast was dependent on the visual environment,indicating attention may influence the apparent contrast by modulating the interaction between the target stimulus and the visual environment.At last,we proposed that the behavioral phenomena could be understood within a single neural framework.