Jennifer Motzer¹, Karen Tian¹, Rachel Denison¹; ¹Boston University

Motivation: Stimuli that appear close together in time compete for representational resources, impairing perception in a phenomenon called temporal competition. Temporal competition can be biased by directing voluntary temporal attention to improve perception at behaviorally relevant moments while diminishing perception at irrelevant moments. It is unknown if this trade-off arises because temporal attention selects among actively competing stimulus representations, such as within working memory, or if temporal attention biases stimulus representations prior to a competitive stage. Here we used a temporal cueing task that independently manipulated temporal attention and temporal competition to test whether attention affects perception even without competition. Methods: Human participants (n=15) performed a challenging perceptual task where we manipulated temporal attention using a precue and temporal competition by varying the number of gratings that appeared on each trial in a single location. Gratings could appear at two possible time points, T1 and T2, separated by 250 ms, in four possible sequences: both present, both absent, or present at either T1 or T2 only. When present, gratings were tilted clockwise or counterclockwise from either the vertical or horizontal axis. On each trial, a precue tone directed attention to either one or both time points. A response cue tone matched the precue on 75% of trials and indicated which time point to report. Participants reported whether or not they saw a grating at the response-cued time point and, if they saw the grating, its tilt. Results: If temporal attention only resolved competition between stimulus representations, it should have improved performance only on two-target trials. However, we found that temporal attention enhanced perceptual sensitivity to a similar degree even without temporal competition, on one-target trials. Therefore, the results suggest that voluntary temporal attention selects stimuli by enhancing perception at attended time points prior to a competitive stage.

Acknowledgements: Startup funds from Boston University to R.D. and National Defense Science and Engineering Graduate Fellowship to K.T.