Figure 1. Saccade Adaptation Paradigm.

(a) Schematic of a trial. The yellow dashed circle represents an observer’s hypothetical gaze location. The observer initially fixates a target Gabor, framed by a black nonius square to aid binocular fusion⁴¹. Once fixation is verified by the eye tracker, the target is shifted 8° leftward (or rightward across blocks), prompting the observer to make a leftward saccade. Saccade initiation is detected online (see Materials and Methods) and, during the saccade, the intra-saccadic target step displaces the target from its pre-saccadic position (dashed white box, not present in the stimulus). In this example, the saccade lands at the pre-saccadic target position, resulting in an oculomotor error signal. (b) Three experimental conditions. The intra-saccadic target step could be outward in both eyes (outward step), inward in both eyes (inward step), or outward in the temporally moving eye and inward in the nasally moving eye (dichoptic step).