Perceptual load modulates the temporal resolution of visual awareness

Abstract

Subjective visual experience depends not only on the spatial arrangement of the environment, but also on the temporal pattern of stimulation. For example, flickering and steady light presented in the same location evoke a very different conscious experience due to their different temporal patterns. Does attention play a role in temporal aspects of visual awareness? Here, we examine whether the availability of processing resources affects the temporal resolution of visual awareness - the ability to distinguish rapid changes in light intensity, detecting visual temporal patterns. According to load theory (Lavie, 1995, 2005), exhausting perceptual capacity in a task will result in reduced awareness of task-unrelated stimuli. Participants detected flicker in a fixated LED which flickered at or around the individually-adjusted critical flicker fusion threshold, while searching for a target letter presented either on its own (low load) or among other letters (high load) in the periphery. A series of experiments showed that the same flickering stimulus was more likely to be categorized as ‘fused’ under high load in the peripheral letter search. We also established the effect of perceptual load on psychophysical measures of sensitivity to flicker, while ruling out alternative accounts such as criterion or stimulus prioritization differences, and differential likelihood of forgetting the correct response under different load conditions. These results are the first to demonstrate that perceptual load determines visual awareness of temporal patterns.

Footnotes

 This research was supported by the Wellcome Trust