Rapid learning of systematic sensory delays around saccades

To establish causality between actions and their sensory consequences, active observers must correctly determine their temporal order. Adaptation to systematic delays between manual movements and sensory events is known to keep such inferences of causality calibrated. Here, we tested whether this mechanism extends to eye movements and resulting sensations. Observers made horizontal saccades across a noise background bandpass-filtered to low spatial frequencies. Saccades triggered a high-contrast, full-field horizontal bar flashing for 4 ms in a time window from 20 to 220 ms after saccade onset. As average saccade durations amounted to 60 ms, flashes occurred during or after saccades. To assess the perceived timing of flashes around saccades, observers reported whether they perceived the flash before or after saccade landing. Two different probability distributions for flash timings were applied in separate blocks: in 60% of trials in each block flashes appeared with a fixed delay of either 20 ms (baseline condition) or 80 ms (delay condition) after saccade onset. In the remaining 40% of trials of each condition, we systematically varied the flash delays with onsets between -40 ms and 160 ms relative to saccade offset. Fitting logistic regressions for each observer and condition, we related participants’ reports to flash timing, and determined the point of subjective simultaneity (PSS) at which the displayed flash was perceived to occur at saccade offset. While PSS estimates varied between participants, all individuals showed a PSS shift towards a later time point in the delay compared to the baseline condition. That is, after exposure to systematic sensory delays, flashes presented right after saccade offset were frequently perceived as occurring during the saccade. This provides evidence that systematic sensory delays associated with saccadic eye movements are rapidly learned, a mechanism that may also establish causality between saccadic eye movements and their natural visual consequences.