Article Figures & Data
Figures
- Figure 1.
Experimental setup and tasks. A, Subjects performed reaching movements on a digitizing tablet using a handheld stylus while looking into a mirror placed between the tablet and a horizontally mounted display. Start positions, targets, and a feedback cursor displayed on the screen were reflected in the mirror. B, Task protocol for experiments 1 and 3. The baseline block was followed by learning trials on which the target-shift created a TPE. This was followed by washout and a final “savings” block on which subjects re-experienced the target-shifts. In experiment 1, the target-shift was 45° (solid line), while in experiment 3, it was 15°, 30°, or 60° (dotted lines) for different groups. In both experiments, three “no-shift” sub-blocks of four trials each were embedded during learning and savings trials; their location is shown using black bars. Verbal instructions were given every time the target conditions were about to change. C, Target locations and sample hand trajectories on early (solid) and late (dotted) learning trials. The original target has been blurred, while the new, shifted target is shown in solid colors. D, In experiment 2, subjects again performed four blocks of trials, but without the no-shift sub-blocks. Additionally, the original target was presented with a ring of numbers as shown on the right. Before each trial, subjects reported the approximate number they would reach to. The original target location always corresponded to number “0,” while the shifted target corresponded to “9.” The ring appeared with the original target and disappeared with the presentation of the new target.
- Figure 2.
TPEs are compensated through intentional strategies. A, Hand deviation (relative to the original target) on the late baseline and first 28 learning trials (each subject shown using a different color). The profile of two subjects is bolded to highlight the variability across subjects. One of them changed movement direction quite early during learning while the other did so quite late. B, Group-averaged hand deviation across trials. Shaded regions denote SEM. Learning (blue) and savings (pink) data are superimposed for ease of comparison; trial 1 corresponds to the first learning trial (or the first savings trial). No-shift trials are highlighted using gray bands. Hand deviation on late baseline, no-shift and early washout trials is shown using open circles. C, Mean hand deviation during early and late learning. Dots represent individual subjects. Error bars are SEM. D, Mean hand deviation on the no-shift sub-blocks and early washout trials. Dots are individual subjects. Error bars are SEM. E, Group-averaged RT across trials. Shaded regions denote SEM. No-shift sub-blocks are highlighted in gray. RT on no-shift trials as well as late baseline and early washout trials, is shown in open circles. F, Mean RT in the baseline and learning blocks. Dots represent individual subjects. Error bars are SEM. G, Change in RT on the no-shift and early washout trials relative to the immediately prior learning trial. Dots represent individual subjects. Error bars are SEM.
- Figure 3.
Strategy-use results in savings. A, Mean hand angle during the early learning (blue) and early savings (pink) phase. Dots represent individual subjects. Error bars are SEM. B, Mean hand angle on late washout and no-shift trials of the savings block. Dots represent individual subjects. Error bars are SEM. C, Average RT on late washout and no-shift trials of the savings block. Dots are individual subjects. Error bars are SEM.
- Figure 4.
Directional changes in response to TPEs are verbalizable. A, Group-averaged hand deviation (blue), reported aiming direction (yellow), and the implicit component (green) across trials. Shaded regions denote SEM. B, Mean trial-wise probability of aim change across learning trials. Shaded regions are SEM. C, Group-averaged hand deviation across trials. Shaded regions denote SEM. Learning (blue, same as in A) and savings (pink) data are superimposed for ease of comparison; trial 1 corresponds to the first learning trial (or first savings trial). Late baseline and early washout trials are shown using open circles. D, Mean hand deviation on early learning and early savings trials. Dots represent individual subjects. Error bars are SEM.
- Figure 5.
Strategies employed to compensate small versus large TPEs are likely dissociable. Group-averaged baseline-corrected hand deviation across trials for the (A) 15°, (B) 30°, and (C) 60° target-shift groups. Shaded regions denote SEM. Other details are same as Figure 2A. D, Mean variance in normalized hand deviation for the three groups. No error bars are shown since this was calculated for the entire group, not individual subjects. E, Mean RT on baseline and learning trials. Dots are individual subjects. Error bars are SEM. F–H, Mean baseline-corrected hand angle on the no-shift sub-blocks of the learning block, early washout trials, and no-shift sub-blocks of the savings block for the (F) 15°, (G) 30°, and (H) 60° target-shift groups. I, Mean hand deviation on the early learning and early savings trials. Dots represent individual subjects. Error bars are SEM.
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