A surprising lack of presaccadic benefits during visual change detection

Even before the eyes move, visual sensitivity improves at the target of the planned eye movement. Yet, it is unknown if such "presaccadic" benefits are merely sensory, or also influence decisional processes. We teased apart these contributions with signal detection theory, and discovered a surprising absence of presaccadic benefits in visual change detection tasks. Participants planned and executed saccades while concurrently detecting and localizing either orientation or contrast changes. Spatial choice bias reliably improved presaccadically but, surprisingly, without a concomitant increase in perceptual sensitivity. Additional investigation with an orientation estimation task, and a Bayesian "variable precision" model, revealed that sensory precision increased at the saccade target, but only for the most recent of two successive stimuli. Moreover, the recent stimulus perceptually biased feature estimates of the prior stimulus, rendering accurate change detection even more challenging. Our results uncover novel perceptual and decisional mechanisms that mediate presaccadic change detection. Lay SummaryPlanning a rapid eye movement (saccade) changes how we perceive our visual world. Even before we move the eyes visual sensitivity improves at the impending target of eye movements, a phenomenon termed "presaccadic attention". We report a surprising lack of such presaccadic attention benefits in a common, everyday setting: change detection. In fact, presaccadic attention renders change detection more challenging by biasing percepts toward the most recent of successive stimuli at the saccade target location. With a Bayesian model, we show how such perceptual and choice biases induced by eye movement planning affect change detection behavior. Our findings may have critical implications for real-world scenarios, like driving, that involve rapid gaze shifts in dynamically changing environments.