Behavior and model predictions for the two-target task.

<p>See <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0033724#pone-0033724-g002" target="_blank">figure 2</a> for details.</p

Model performance for the one-target task.

<p>Test error of standard model minus test error of extended model for all subjects and noise amplitudes. Values are given as the median over 100 cross-validation runs. The lower and upper error bars represent the 25 and 75 percentile, respectively. A positive value means that the extended model gave a better fit than the standard model. A value of zero means that there was no difference between the models. Conditions for which the extended model gave a significantly better prediction than the standard model are indicated by or . Subject S5 was discarded (see <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0033724#s2" target="_blank"><i>Methods</i></a>).</p

Schematic of the tasks.

<p>(a) In the one-target task (left panel), subjects had to control a joystick to move a ball on a screen to hit a target (rectangle) at time s. The ball (circle) started at a random vertical position between and 0.5 at the left of the screen and moved at a constant horizontal velocity to the right. Subjects could move the ball up- or downwards. Gaussian white noise was superimposed on the vertical ball position to introduce uncertainty about future ball positions. The dashed line illustrates the trajectory of the ball. (b) In the two-target task (right panel), two targets were present at vertical positions and 0.5. The ball started at vertical position at the left of the screen. Subjects were asked to steer to one of the targets and they were free to choose which one. All other experimental conditions were exactly the same as for the one-target task. (c) Ball position time traces (100 trials) of subject S6 performing the one-target task with noise amplitude . (d) Same for the two-target task. (e) Control signal time traces corresponding to the ball position time traces in panel c (100 trials) of subject S6 performing the one-target task with noise amplitude . (f) Same for the two-target task.</p

Behavior and model predictions for the one-target task.

<p>Top panels: average ball position displayed as mean (gray solid line) and standard deviation (gray shaded area) for all noise amplitudes (rows) and subjects (columns). The black dashed and solid line represent the average fit of the standard model and the extended model, respectively. Bottom panels: same for the control signal. Subject S5 was discarded (see <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0033724#s2" target="_blank">Methods</a>).</p