Fig 4. Boxplots showing within-participant variation as an index of stability.

Top: within-participant IQR for the hand performing tapping (left) and the hand performing sawing (right), for both the single handed task (‘single’) and the dual movement tasks (remainder). Bottom, left: participant-specific difference between within-participant variation for the hand performing tapping and the hand performing sawing. Dashed line: no difference in variation. Bottom, right: participant-specific ratio of the variation observed during the single hand task compared to the equivalent action in the four dual movement tasks. Dashed line: no difference in variation. A value of 0.5 corresponds to half the amount of variation in the single hand task, a value of 2 corresponds to twice the variation. For further details on experimental conditions and legend, please refer to Fig 2.