Table 1. Summary of analysis steps of the eye movement data.

Analysis step		Description
Pre-processing	1. Filtering	Maximally flat 2nd order low-pass filter without delay and 9-sample wide edge enhancing smoothing kernel
	2. Artefact removal	Removal of samples between 0.10 seconds before and 0.25 seconds after a blink artefact
Saccadic detection	1. Detect approximate saccadic intervals	Samples with acceleration >2.576*SD of acceleration distribution
	2. Merging of saccadic intervals	Intervals closer than 20 ms
	4. Detect onset and offset of saccade	From highest velocity check consecutive samples in backward and forward direction, onset or offset if 1 of 3 criteria satisfied: 1. Sample to sample direction deviation from main direction (which is the sample-to-sample direction at highest velocity) of >60 degrees 2. Sample to sample directional change between two adjacent samples of >20 degrees per ms of sample duration 3. Velocity of <5 degrees/second
	5. Minimal saccadic amplitude and duration	Amplitude of >0.15 degrees and duration of >8 ms
	6. Determine the main saccade	Saccade with the highest peak velocity of a saccadic interval
Parameters calculation	Fixation task	Fixation periods: mean and SD of gaze, vergence and velocity. Median and IQR of total velocity. Bivariate contour ellipse area. Linear fit coefficient and standard error of estimate. Number of saccadic intrusions (divided in square wave jerks (SWJ) and saccades) per second. Mean amplitude of saccadic intrusion. Mean inter-SWJ interval.
	Pro-saccadic, express saccadic and repeated pro-saccadic tasks	Centrifugal saccades: peak velocity, peak acceleration, gain, latency, firstpass gain (FPG), area under the curve of the saccadic trajectory (AUC). Versional dysconjugacy index (VDI) of: peak velocity, peak acceleration, FPG and AUC.
	Anti-saccadic task	Centrifugal saccades: peak velocity, peak acceleration, latency, gain, X error, proportion of errors. Final eye position: gain, X error.
	Double-step saccadic task	First and second saccade: peak velocity, peak acceleration, latency/intersaccadic interval, amplitude/gain. Final eye position: gain, X error, Y error. Proportion of correct, acceptable, contraversive shifted and late double-step saccades. Proportion of first saccade to second target