Temporal expectation hastens sensory encoding but does not affect evidence quality

The ability to predict the timing of forthcoming events, known as temporal expectation, has a strong impact on human information processing. Although there is growing consensus that temporal expectations enhance perception, it remains unclear whether they affect the decision process itself, or non-decisional (sensory / motor) processes. Here, participants used predictive auditory cues to anticipate the timing of low-contrast visual imperative stimuli. Modelling of the behavioral data indicated that temporal expectations speeded up non-decisional processes but had no effect on decision formation. Electrophysiological recordings confirmed and extended this result: temporal expectations hastened the onset of a neural signature of decision formation, consistent with faster sensory encoding, but had no effect on its build-up rate. Anticipatory alpha-band power was modulated by temporal expectation, and co-varied with intrinsic trial-by-trial variability in behavioral and neural signatures of sensory encoding speed. These findings highlight how temporal predictions optimize our interaction with unfolding sensory events.