Fig 1.
A: Training schedules of the three visuomotor adaptation experimental groups. Note that the schedule for each task in ALT is the same as the single task schedule in LONG-ITI. The only difference between ALT and LONG-ITI is the second task (T2) is intercalated between two presentations of the first task (T1). B: The experiment consisted of three blocks: 30 baseline trials, 60 training trials per task (which depend on the condition, as shown in A), and retention test trials, given in blocks of 5 trials at 2 min, 5 min, and 10 min after the end of training trials. C: Distribution of targets: Targets randomly appeared either upward or leftward depending on a task with a color cue, green or blue. To hit a target, subjects had to adapt to the altered the mapping between the hand position and the cursor position via either a counterclockwise (CCW: +45°) visuomotor rotation or a clockwise (CW: -45°) rotation depending on a task.
Table 1.
Each of candidate models was fitted to all the data from the three groups (N = 300). For the groups with one task, SHORT-ITI and LONG-ITI, the interference parameters were ignored in models.
Fig 2.
Observed subject behaviors in three experimental conditions.
SHORT-ITI (A), LONG-ITI (B), and ALT (C). Star symbols: median subject performance. Shaded area: inter-quartile (25–75%) ranges.
Fig 3.
Comparison of initial learning and retention.
A: Initial learning rates (performance increase per trial) obtained from the initial 15 trials in the training block. B: Forgetting in the two minute post-training. Forgetting was measured as a difference between zero and two minute retention tests post-training (see Methods). C: Overall retention in 0, 2, 5, and 10 minute post-training. In Fig 4A and 4B, circles indicate performance of individual subjects.
Fig 4.
Estimated effects of time and/or interference on between-trial forgetting with data and predictions from the three selected models.
A: Time effect as the difference in training performance between SHORT-ITI and LONG-ITI. B: Interference effect as the difference in training performance between and LONG-ITI and ALT. C: Combined effect of time and interference as the difference in training performance between SHORT-ITI and ALT. Black: data, blue: model 4 (two interfering fast processes and two independent slow processes), green: model 5 (two independent fast processes and two interfering slow processes), red: model 6 (two interfering fast processes and two interfering slow processes). Dots and lines indicate the means, shaded areas indicate the ± S.D. from 10,000 bootstrapped samples.
Table 2.
Results of the model comparison analysis.
For the tested models described in Table 1, BICs and the confidence intervals of the estimated parameters from 10,000 bootstrapped data sets were presented. BIC of models 4, 5, 6 with interference parameter(s) was significantly lower than that of the other models.