Abstract
Crowding is a phenomenon in which recognition of a visual target is impaired by other similar visual stimuli (distracters) presented near the target. Crowding effect may be due largely to insufficient spatial attentional resolution. We measured orientation selective adaptation to ‘crowded’ illusory lines in two attentional conditions. In ‘attended’ condition, subjects were instructed to covertly attend to the location of adapting target stimulus during the adaptation period. In ‘non-attended’ condition, subjects performed an attentive task at the fixation point throughout the adaptation phase. The results showed that the magnitude of adaptation in the attended condition was significantly greater than that in the non-attended condition. Therefore, attention could subliminally enhance orientation selective adaptation to illusory lines in the crowding condition where target-distractor separation is beyond the spatial resolution limit of attention. Despite traditional close link between attention and awareness, here we provided evidence about subliminal attentional modulation for stimuli, which could not be consciously perceived.
The authors wish to thank Dr. Seyed-Reza Afraz for his helpful comments on the manuscript.