Suraj Kumar¹ (), Narayanan Srinivasan¹; ¹Indian Institute of Technology Kanpur

Is visual awareness, especially perception of gist of natural scenes, graded? Also, does attention influence gradedness? Recently, we showed that perceptual load of a secondary task influences gradedness of visual awareness of scene gist. Awareness was more graded under high perceptual load condition compared to low perceptual load. Carrasco and colleagues have already shown that both exogenous and endogenous attention influence subjective appearance of content. However, it is still not clear whether exogenous/endogenous attention influence appearance in a graded or discrete fashion. Hence, we conducted two experiments in the current study in which we manipulated attention (exogenous cuing in experiment-1 and endogenous cuing in experiment-2). In both these experiments, we presented natural scene images with varying contrast to obtain psychometric curves while participants performed a scene discrimination (Type-1) task and perceptual awareness rating (Type-2) task. Exogenous cue was not predictive of spatial location, while endogenous cue predicted spatial location. A natural scene image (indoor or outdoor) was presented either to the left or to the right of fixation. A four-parameter model was fitted for valid, invalid, and neutral conditions in both the experiments. Previous studies have used changes in the slope of the psychometric function to infer for degrees/gradedness of awareness. As expected, we found differences in threshold as a function of cuing indicating that attention influences appearance. Moreover, endogenous cuing but not exogenous cuing significantly influenced the slope parameter of the psychometric curves for perceptual awareness ratings. Slope for invalid and neutral conditions were higher compared to the valid condition with awareness ratings; gist perception is less graded with endogenous attention. These findings show that while exogenous spatial attention does not influence gradedness of visual awareness of scenes, endogenous attention does. Taken together these results support graded theories of visual awareness and also show that attention influences gist appearance.