Abstract
The relationship between attention and conscious perception is an important topic in understanding mechanisms of conscious perception. Hypotheses emphasizing the role of cognitive access in conscious perception argue that attention and conscious perception are closely related. On the other hand, hypotheses separating conscious perception from cognitive access argue that attention and conscious perception are dissociable. To investigate the relationship between attention and conscious perception, studies have used a spatial cueing paradigm that compares conscious reports (e.g., visibility rating) on cued and uncued trials. Spatial cueing, however, has a limitation because observers have awareness of which trial is the cued or uncued trial, which can affect decision criteria of conscious report regardless of conscious perception of a target. To solve this problem, we used a monocular cueing paradigm. A monocular cue can attract eye-specific attention to a cued eye, but observers have no awareness of which eye received the cue and thus they do not know which trial is cued. In the present study, the effect of eye-specific attention was tested by comparing objective performances (i.e., orientation discrimination of a Gabor patch) between cued and uncued trials where a target was presented to the cued and uncued eyes respectively. At the same time, we compared conscious reports (i.e., visibility rating of a Gabor patch) to investigate whether eye-specific attention can modulate conscious perception. We found that eye-specific attention enhanced both objective performances and conscious reports of a target. Through an additional experiment that compared conscious reports when objective performances were matched between the cued and uncued trials, we again found that the effect of eye-specific attention on conscious perception is difficult to separate from the effect on objective performances. Our results suggest that attention and conscious perception are closely related, and that attention can act as a gateway to conscious perception.