Abstract
Predictive coding theories of perception posit that unexpected events trigger prediction errors and updating of predictive models. Here, we sought evidence for prediction errors elicited by task-irrelevant abrupt onsets that capture attention exogenously. The main question of this study is whether violations of expectation regarding a task-irrelevant onset modulate its exogenous cueing effects and whether those effects are temporally contingent. Participants discriminated the orientation of a Gabor patch that was preceded, on some trials, by a task-irrelevant disk (the exogenous cue). The color of two small fixation squares (red or green) implicitly signaled the probability that a disk would appear (0.8, “expected”, or 0.2, “unexpected”). When presented, this disk flashed briefly, either near the target Gabor (valid cue) or near a distractor Gabor (invalid cue, equally likely). To characterize the temporal dynamics of any expectation-based effects, we required participants to respond during a fixed, 500ms response window, which was open at seven different delay intervals (33ms-2133ms, after the offset of the target and distractor gratings). This allowed us to generate a full speed-accuracy tradeoff (SAT) function, describing the accumulation of decision evidence over time. Seven participants completed ~15,000 trials each, spread out over 17-20 experimental sessions. We found that unexpected disks produced significantly larger cueing effects (Δaccuracy, valid–invalid) than expected disks, but only at the shortest response delay. These results suggest that implicitly generated expectations concerning task-irrelevant stimuli transiently modulate the reflexive allocation of attention, which jointly modulate visual processing.