Temporal attention improves perception without enhancement by temporal competition

Abstract

When successive stimuli occur close enough together in time, their perception can be impaired. Such impairments indicate temporal competition between successive stimuli for processing resources. Voluntary temporal attention can bias processing resources in favor of a behaviorally relevant moment, improving perception at the attended time at the expense of impairments at unattended times. However, it is unclear whether these perceptual tradeoffs across time arise because voluntary temporal attention selects among actively competing stimulus representations, such as within visual working memory, or if, instead, temporal attention facilitates stimulus processing prior to a competitive stage. Here we used a temporal cueing task with up to two grating targets in succession to test whether and how the effects of temporal attention depend on temporal competition. Participants reported whether at a probed time the target was present or absent, and if present, performed a difficult orientation discrimination judgment. To isolate the effects of voluntary temporal attention from those of temporal expectation, we manipulated the task-relevance of the two possible target times while controlling stimulus timing predictability. Temporal competition was manipulated via stimulus presence or absence at the unprobed time. We found that voluntary temporal attention improved perceptual discriminability even in the absence of temporal competition, when only one stimulus appeared during the trial. Critically, the magnitude of attentional enhancement was comparable with and without temporal competition. These results suggest that voluntary temporal attention enhances perception by facilitating processing prior to a competitive stage, rather than by resolving conflicts between actively competing stimulus representations.