Figure 1.

Task design. (A) Shortening and lengthening estimation phase: (Top row) No-saccade condition trial. Subjects were instructed to fixate at the blue fixation target shown as a small circle. After 1 second, a bar was flashed (gray rectangle) for 1 second; following an acoustic signal, subjects had to indicate (while maintaining fixation) the perceived size of the bar by the grip aperture. (Bottom row) Saccade condition trial. Subjects fixated at the green fixation target. After 1 second, a bar was projected for 1 second. An acoustic signal was then activated, prompting the subject to perform a saccade toward the bar and thereafter indicate the perceived size of the bar. As soon as the start of the saccade was detected, the bar disappeared from the screen. (B) Saccadic size-change phase: (Top row) Shortening size-change phase. At the beginning of the trial, the red fixation target was presented, and the subject's gaze was directed toward it. After 1 second, a red bar appeared, but the subject had to continue to fixate at the fixation target. After a randomized time (1–1.8 second), an acoustic signal informed the subject to execute a saccade toward the bar. As soon as the saccade was detected, the bar was symmetrically decreased in size by 30% of its length. (Bottom row) Lengthening saccadic size-change phase, which was structured in the same way as the shortening saccadic size-change phase, with the difference that the bar was symmetrically increased in size by 30% during saccade execution. (C) Replication experiment: (Left) The no-saccade condition and saccade condition were the same as for the shortening and lengthening size-change estimation phases in A, but the bars presented were horizontally oriented. (Right) The shortening and lengthening adaptation phases, for which the task sequence was the same as in B, but saccades were performed to horizontal bars that decreased and increased, respectively, but not symmetrically (Bosco et al., 2015).