Data from Murdison et al. (2019): Saccade-induced changes in ocular torsion reveal predictive orientation perception

Participants Eight adults with normal or corrected to normal vision performed the experiment (five males, three females; age range 20–30 years). Participants were paid for their participation and were all naïve to the purpose of the experiment, and all had previous experience with psychophysical experiments involving video eye tracking. Each participant gave informed written consent prior to the experiment. All procedures used in this study conformed to the Declaration of Helsinki. Materials Stimuli were computer-generated using the Psychophysics Toolbox (Brainard, 1997) within MATLAB (MathWorks, Natick, MA), and were projected onto a large 120 cm (81°) × 90 cm (65.5°) flat screen by means of a DS+6K-M Christie projector (Christie Digital, Cypress, California) at a frame rate of 120 Hz and a resolution of 1152 × 864 pixels. Participants sat in complete darkness 70 cm away from the screen, and a table-mounted chin rest supported their heads. The complete darkness was required to prevent participants to perceive a compression of space, which might have confounded our data by causing all orientations being perceived closer to vertical than they were (Krekelberg, Kubischik, Hoffmann, & Bremmer, 2003; Lappe, Awater, & Krekelberg, 2000; Morrone, Ross, & Burr, 1997). Eye movements were recorded using an infrared video-based Eyelink II (SR Research, Ottawa, Ontario) that was attached to the chin rest, providing a table-fixed head strap that kept each participant's head in a constant position throughout each experimental session. The screen was viewed binocularly, and eye position was sampled at 500 Hz. Prior to each block, participants performed a 13-point calibration sequence over a maximum eccentricity of 25°. The eye to which the perceptual stimulus was fovea-locked for each block was selected based on calibration performance. Drift correction was performed offline every 10 trials, based on a central fixation position. To ensure precise temporal measurement of trial start and stimulus presentation, we positioned a photosensitive diode over the lower left corner of the screen, where we flashed a white patch of pixels both at the start of each trial and at the presentation of the oriented bar stimulus (at the current on-screen gaze position of the participant). This part of the experimental apparatus was occluded from the view of the participant. After calibration for constant data acquisition delays, the photosensitive diode's voltage spikes provided reliable es