Gradedness of gist perception with scenes depends on concurrent task load: awareness under high load is more graded due to noise suppression.

There is growing evidence that the visual awareness of objects is graded. However, it is unclear whether scene perception is graded and whether attention modulates that gradedness. We addressed these questions in two experiments in which participants identified scenes as indoor or outdoor. Attention was manipulated using a concurrent perceptual load (low or high) task. Scene contrast (Experiment 1) and noise added to scenes (Experiment 2) were manipulated in the study. Participants made a four-point perceptual awareness scale (PAS) rating following the scene judgment. The data on the accuracy of the scene judgments and the mean PAS ratings as a function of contrast (Experiment 1) or noise (Experiment 2) were fitted with a four-parameter logistic function. We predicted lesser PAS rating function slopes in the high-load condition, indicating more graded awareness. Scene perception was better (lower threshold) under low load across experiments indicating more attentional resources benefit scene processing. Crucially, PAS function slopes were shallower under high load in both experiments, indicating that awareness becomes more graded when attentional resources are limited. In Experiment 2, accuracy at high noise levels (the lower asymptote) was higher in the high load condition suggesting that high load suppresses external noise during scene perception. The difference in the lower asymptote for accuracy between load conditions correlated negatively with the difference in PAS ratings slope linking noise suppression to the gradedness effect. Together, these findings support a graded account of visual awareness and demonstrate that attention modulates scene perception clarity by suppressing external noise.