Figure 5.

Precision in amplitude and angle. (A) Decomposition of variability on the two axes parallel and orthogonal to the saccade, ${\sigma }_r$ and ${\sigma }_{\varphi }$. The black line represents the average saccade trajectory, the red circle gives the position of the target, and the blue dots are the landing positions of individual saccades. The 95% confidence ellipse is also shown. (B–E) Values of ${\sigma }_r$ (B), ${\sigma }_{\varphi }$ (C), angular precision (D) and scatter ratio ${\sigma }_r/{\sigma }_{\varphi }$ (E) as a function of target eccentricity. Error bars represent SEM. The three lines refer to saccades in different directions. In (E), the dashed line represents a spherical distribution; the scatter plots are the 2D landing distributions and their 95% confidence ellipses for one subject.