Trial-to-trial variances related to eye velocities and experimental conditions: A. Left eye; B. Right eye. Standard deviation (SD) within each subject is averaged among all subjects for the saccade toward the left (red lines) and right (blue lines) for the sessions of Go-Only (solid lines) and Go/NoGo (dashed lines), on the 1st day (left panels) and 2nd day (right panels). Horizontal axes are the latency from saccade initiation. The latencies of significantly larger variances are denoted by black square brackets for the abducting saccade relative to the adducting, by red square brackets for the leftward saccade relative to the rightward, and by green square brackets for the saccades in the Go/NoGo sessions than the Go-Only. The significant differences were calculated by ANOVA factoring the saccade direction, the session type, the experiment day and the subject (p < 0.05 for 10 ms or more). To see the difference between the Go/NoGo and Go-Only sessions, see Supplementary figure 3A and B in Additional file 3. C. Time course comparisons between the eyes were based on the significant differences. The latency of significant differences between the abducting and adducting saccades are shown by black horizontal bars. The onsets of the significant dependencies are linked between the eyes by a thin black line, showing eye yoking. Linked horizontal bars in red indicate the yoking found based on the significant difference between the leftward and rightward saccades, and that in green showed the significant effect of cognitive load.