Abstract: PURPOSE: In the past, some scholars had found that the effect of exogenous attention on perceptual impression changes dynamically with stimulus contrast (Zhou, Buetti, Lu & Cai, 2018). When the stimulus contrast is low, exogenous attention enhances the subjective contrast of the stimulus, while when the stimulus contrast is high, exogenous attention weakens the subjective contrast. Here, we investigated the influence of endogenous attention on perceptual appearance of high- and low-contrast gratings.
METHODS: In this experiment, we used a rapid serial visual presentation (RSVP) task and a cue to direct endogenous spatial attention, and participants performed an equality judgment task, in which they reported whether two Gabors are of the same or different contrast. For the high contrast grating, the contrast of the test stimulus was 60%, and the contrast of the test stimulus was systematically varied in 11 log increments from 29% to 97%; For the low contrast grating, the contrast of the standard stimulus was 25%, and the contrast of the test stimulus was systematically varied in from 9% to 68%.
RESULTS: For both high-contrast and low-contrast gratings, the average Point of Subjective Equality (PSE) for the test-cued condition (i.e., the test stimulus was cued) was lower than standard-cued condition (i.e., the standard stimulus was cued).
CONCLUSIONS: Our result suggests that voluntary attention enhances perceptual contrast both at both low contrast level and high contrast level. This is in contrast with previous research of involuntary attention, in which contrast appearance was enhanced for low-contrast stimuli while reduced for high-contrast stimuli.

Key words: endogenous attention, contrast, appearance