Visuomotor Adaptation in a Viewing Window Task Figure 3. Comparisons of behavioural measures between groups during distorted trials. A) Subjects in the gradual rotation group demonstrated significantly faster (F(1,38) = 5.406, p,0.05) mean velocities than those in the sudden rotation group. B) Subjects in the sudden rotation group spent a slightly longer (but not significant) time scanning the images prior to indicating their identification. C) Subjects in the sudden rotation group spent significantly more time (F(1,38) = 4.620), p,0.05) with the Viewing Window off of the object than those in the gradual rotation group. doi:10.1371/journal.pone.0048759.g003 a simpler scan path with fewer changes in direction. When the distortion is removed, the sudden rotation subject shows a much smaller after-effect compared to that observed in the gradual rotation subject. Quantitatively, these observations can also be made with the examined behavioural measures. Both groups demonstrated reductions in movement velocity that were significant by phase (Figure 5A, F (2,76) = 14.890, p,0.01). Overall, there was not a significant interaction between phase with distortion type for mean movement velocity (F (2,76) = 1.486, p.0.05). Relative to the pre distortion period, a slight (but not significant, p = 0.078) increase in scan time was observed in the sudden rotation group in the early phase (Figure 5B). Both groups demonstrated significant reductions in scan times in the post distortion phase (p,0.05), however, this reduction was slightly larger in the sudden rotation group. Overall, there was a significant effect of phase (F (2,76) = 43.396 = p,0.01) but not a significant interaction between phase with distortion type for mean scan time (F(2,76) = 2.463, p.0.05). A significant interaction between phase and distortion type was found for the amount of time that the Viewing Window spent off the object (F(2,76) = 10.320, p,0.001, Figure 5C). Relative to the early phase, subjects in the sudden rotation group demonstrated greater difficulty in controlling Viewing Window movement compared to those in the gradual rotation group as evidenced by a greater percentage of time spent off the object (Figure 5C). Both groups demonstrated significant differences compared to their baseline values (p,0.05). During the post distortion phase, subjects in the sudden rotation group spent significantly less time off the object (p,0.05). Discussion We hypothesized that the Viewing Window task could be used to investigate two mechanisms of adaptation. To do this, we identified measurable differences in behaviour in two experimental groups eliciting strategic control and spatial realignment. When comparing behavioural measures during all distortion trials of the two groups, we found significant differences in the movement velocities, and time that the Viewing Window spent on areas in which there was no object. This demonstrates the ability to distinguish quantitative differences in behaviour between the use of strategic control and spatial realignment within a novel, engaging computer-based task for studying visuomotor adaptation. No significant difference was observed between scan times however, this aspect of behaviour is also influenced by the perceptual component of the task. While the existence of between group differences during distortion trials is interesting, PLOS ONE | www.plosone.org 5 November 2012 | Volume 7 | Issue 11 | e48759