**Participants.** 20 participants will be recruited through word of mouth and campus mailing lists. Each participant will complete one session of approximately 1 hour. Participants will receive 8 Euros per session. We will obtain written informed consent from all subjects prior to inclusion in the study. **Apparatus.** The experiment will take place in a sound-attenuated, dark room. Stimuli will be presented on gamma-calibrated 16:9 ViewPixx 3D monitor (Vpixx Technologies, Saint-Bruno, QC, Canada), running at a resolution of 1920 x 1080 pixels (52 cm screen width) at a refresh rate of 120 Hz. Participants will be seated in front of the monitor supported by a chin-rest at a distance of 57 cm. The experimental code is implemented in MATLAB 2016b (Mathworks, Natick, MA, USA), using the Psychophysics and Eyelink toolboxes (Kleiner et al., 2007; Cornelissen et al., 2002) and runs on a Dell Precision T7810 Workstation with a Ubuntu 18.04 operating system. Eye movements of the participant's dominant eye are recorded via a Eyelink 1000 tabletop system (SR Research, Osgoode, ON, Canada) at a sampling rate of 1000 Hz with no link filter and normal data filter. Responses are collected with a standard US-english keyboard. **Stimuli.** All natural images were extracted from the SYNS database (Adams et al., 2016). From each available panoramic HDR image, we extracted 9 non-overlapping single images, rescaled them to a resolution of 1921 x 1281 pixels (using bicubic interpolation and keeping their initial aspect ratio) and converted them to JPG images. As 90 panoramic images were available, this procedure resulted in 9 sets of 90 images each. 8 out of 9 sets will be randomly selected for each experimental session and each set will be then randomly assigned to a Color x Presentation Duration sub-condition (see below). Within each of these sub-conditions, the set will be again shuffled and then split into two halfs: One to be presented with matching, one to be presented with non-matching post-saccadic images. This procedure will lead to the side-effect that each image of the set will be presented exactly once during the saccade, but each second image of the set will be presented twice after the saccade (i.e., once with matching and once with non-matching intra-saccadic scenes. Fixation markers will be maximum-luminance white squares with black center of 0.4 dva width and height. Saccade target markers will be similar, but twice as large as fixation markers. Background color will be minimum-luminance black. **Procedure.** Each trial will start with the presentation of the fixation marker (left side of screen at 8 dva horizontal eccentricity relative to screen center) and the saccade target marker (right side of screen at 8 dva horizontal eccentricity) displayed on a black background. After 450 ms of successful fixation within a circular boundary with a radius of 2 dva around the center of the fixation marker (trial abort after 2 seconds of not fixating or 20 refixations), the backlight of the monitor will be turned off, which constitutes the cue to make a saccade to the previously presented location of the saccade target. In the meantime, while the backlight is turned off, the image of the scene is presented, but invisible to the observer. As soon as the saccade is detected (see Online saccade detection), the tachistoscopic presentation schedule will be initiated, i.e., the backlight of the screen will be turned on for the defined presentation duration and then turned back off. If no saccade is detected within a time window of 2.5 seconds after cue onset, then the trial will be aborted. The post-saccadic presentation will be initiated 500 ms after the backlight is turned off during the intra-saccadic presentation: The same or a different visual scene will be presented for the same (as intra-saccadic) presentation duration. Right after this post-saccadic presentation is concluded, the observer will be able to respond using RightArrow (same scene) and LeftArrow (different scene), which also triggers the reactivation of the monitor's backlight. Feedback will be given if gaze position did not fall within a 3 dva circular boundary around the saccade target ('Saccade did not reach the target area'), if 2 or more saccades were made ('Please make one saccade (you made XX)'), or if a wrong response key was pressed ('Wrong response key pressed.'). Trials, in which any of these events were detected, will be appended to the list of trials total. One session will be subdivided in 8 blocks. **Design.** Each session will consist of 720 trials (45 trials per experimental cell). The number of trials is determined by the following experimental factors: - Presentation duration (4 levels). Intra- and post-saccadic presentations will have one of four possible durations, i.e., 8.3 ms, 16.7 ms, 25 ms, or 33.3 ms. - Availability of color (2 levels). Stimuli will be either presented as color or grayscale images. - Identity of scene (2 levels). Post-saccadic and intra-saccadic scenes will either be the same or different. **Online saccade detection.** Online saccade detection will be performed using the algorithm described by Schweitzer & Rolfs (2019) with the parameters θ=40, λ=15, and k=2. In each trial, all samples collected since the beginning of the fixation onset were used to compute the two-dimensional velocity thresholds. **Tachistoscopic Display.** We validated the timing behavior of the ViewPixx monitor's Tachistoscopic (Tscope) mode using a LM03 photometer recording at a sampling rate of 2000 Hz, while displaying on-off-flicker at four different on-durations (8.3, 16.7, 25, 33.3 ms) and a constant off-duration of 8.3 ms (1200 trials for each on-duration). Results are shown below. In addition, we used a reference LED that was turned off as soon as the presentation schedule began to estimate the onset latency of the schedule: The onset latency must have been below 0.5 ms, as onsets of schedules and the reference LED occurred in the same sample. Mean absolute errors were also below 0.5 ms and were likely induced by the sampling rate of the photometer and not the Tscope mode. Code is provided in the folder "Tscope measurements". ![Tscope measurements][1] **References** Adams, W. J., Elder, J. H., Graf, E. W., Leyland, J., Lugtigheid, A. J., & Muryy, A. (2016). The southampton-york natural scenes (syns) dataset: Statistics of surface attitude. *Scientific reports, 6*, 35805. Cornelissen, F. W., Peters, E. M., & Palmer, J. (2002). The Eyelink Toolbox: eye tracking with MATLAB and the Psychophysics Toolbox. *Behavior Research Methods, 34*(4), 613-617. Engbert, R., & Mergenthaler, K. (2006). Microsaccades are triggered by low retinal image slip. *Proceedings of the National Academy of Sciences, 103*(18), 7192-7197. Kleiner, M., Brainard, D., Pelli, D., Ingling, A., Murray, R., & Broussard, C. (2007). What’s new in Psychtoolbox-3. *Perception, 36*(14) Schweitzer, R., & Rolfs, M. (2019). An adaptive algorithm for fast and reliable online saccade detection. *bioRxiv,* 693309. Shi, L. (2017). An Evaluation of an LCD Display With 240 Hz Frame Rate for Visual Psychophysics Experiments. i-Perception, 8(5), 2041669517736788. [1]: https://mfr.de-1.osf.io/export?url=https://osf.io/5uw7h/?action=download&mode=render&direct&public_file=False&initialWidth=848&childId=mfrIframe&parentTitle=OSF%20%7C%20Tscope_measurements.png&parentUrl=https://osf.io/5uw7h/&format=2400x2400.jpeg