Differing Dynamics of Intrapersonal and Interpersonal Coordination: Two-finger and Four-Finger Tapping Experiments

Abstract

Finger-tapping experiments were conducted to examine whether the dynamics of intrapersonal and interpersonal coordination systems can be described equally by the Haken-Kelso-Bunz model, which describes inter-limb coordination dynamics. This article reports the results of finger-tapping experiments conducted in both systems. Two within-subject factors were investigated: the phase mode and the number of fingers. In the intrapersonal experiment (Experiment 1), the participants were asked to tap, paced by a gradually hastening auditory metronome, looking at their fingers moving, using the index finger in the two finger condition, or the index and middle finger in the four-finger condition. In the interpersonal experiment (Experiment 2), pairs of participants performed the task while each participant used the outside hand, tapping with the index finger in the two finger condition, or the index and middle finger in the four-finger condition. Some results did not agree with the HKB model predictions. First, from Experiment 1, no significant difference was observed in the movement stability between the in-phase and anti-phase modes in the two finger condition. Second, from Experiment 2, no significant difference was found in the movement stability between the in-phase and anti-phase mode in the four-finger condition. From these findings, different coordination dynamics were inferred between intrapersonal and interpersonal coordination systems against prediction from the previous studies. Results were discussed according to differences between intrapersonal and interpersonal coordination systems in the availability of perceptual information and the complexity in the interaction between limbs derived from a nested structure.

Fig 1. Two within-subject factors.

Phase mode: left, in-phase mode; right, anti-phase mode. Number of fingers: top, two-finger; bottom, four-finger.

Fig 2. Experimental setup of Experiment 1.

Experimental setup of an intrapersonal experiment.

Fig 3. Schematic diagram portraying the temporal relation between taps and beats.

L, left hand tap; R, right hand tap; ♪, metronome beat; Time elapses from left to right.

Fig 4. Percentage of phase transition occurrence.

Colors of bar indicate how many times the taps in the opposite phase mode repeated. From black (5 times), … to the lightest gray (2 times). 2f-in: two-finger in-phase condition, 2f-an: two-finger anti-phase condition, 4f-in: four-finger in-phase condition, 4f-an: four-finger anti-phase condition.

Fig 5. SD of relative phase.

Circle marker/rigid line represents two-finger in-phase condition, 2f-in; Triangle marker/rigid line represents two-finger anti-phase condition, 2f-an; Circle marker/dashed line represents four-finger in-phase condition, 4f-in; Triangle marker/dashed line represents four-finger anti-phase condition, 4f-an. Error bars represent the standard deviation.

Fig 6. Cross recurrence plots.

Cross recurrence plots of sample data for each of four conditions. Left-top, two-finger in-phase condition; Right-top, two-finger anti-phase condition; Left-bottom, four-finger in-phase condition; Right-bottom, four-finger anti-phase condition.

Fig 7. %Recurrence.

Circle marker/rigid line represents two-finger in-phase condition, 2f-in; Triangle marker/rigid line represents two-finger anti-phase condition, 2f-an; Circle marker/dashed line represents four-finger in-phase condition, 4f-in; Triangle marker/dashed line represents four-finger anti-phase condition, 4f-an. Error bars represent the standard deviation.

Fig 8. Average line length.

Circle marker/rigid line represents two-finger in-phase condition, 2f-in; Triangle marker/rigid line represents two-finger anti-phase condition, 2f-an; Circle marker/dashed line represents four-finger in-phase condition, 4f-in; Triangle marker/dashed line represents four-finger anti-phase condition, 4f-an. Error bars represent the standard deviation.

Fig 9. Average Relative Phase Distribution.

Circle marker/rigid line represents two-finger in-phase condition, 2f-in; Triangle marker/rigid line represents two-finger anti-phase condition, 2f-an; Circle marker/dashed line represents four-finger in-phase condition, 4f-in; Triangle marker/dashed line represents four-finger anti-phase condition, 4f-an. Error bars represent the standard deviation.

Fig 10. Experimental setup of Experiment 2.

Experimental setup of an interpersonal experiment.

Fig 11. Percentage of phase transition occurrence.

Colors of bar indicate how many times the taps in the opposite phase mode repeated. From black (5 times), … to the lightest gray (2 times). 2f-in: two-finger in-phase condition, 2f-an: two-finger anti-phase condition, 4f-in: four-finger in-phase condition, 4f-an: four-finger anti-phase condition.

Fig 12. SD of relative phase.

Circle marker/rigid line represents two-finger in-phase condition, 2f-in; Triangle marker/rigid line represents two-finger anti-phase condition, 2f-an; Circle marker/dashed line represents four-finger in-phase condition, 4f-in; Triangle marker/dashed line represents four-finger anti-phase condition, 4f-an. Error bars represent the standard deviation.

Fig 13. Cross recurrence plots.

Cross recurrence plots of sample data for each of four conditions. Left-top, two-finger in-phase condition; Right-top, two-finger anti-phase condition; Left-bottom, four-finger in-phase condition; Right-bottom, four-finger anti-phase condition.

Fig 14. %Recurrence.

Circle marker/rigid line represents two-finger in-phase condition, 2f-in; Triangle marker/rigid line represents two-finger anti-phase condition, 2f-an; Circle marker/dashed line represents four-finger in-phase condition, 4f-in; Triangle marker/dashed line represents four-finger anti-phase condition, 4f-an. Error bars represent the standard deviation.

Fig 15. Average line length.

Circle marker/rigid line represents two-finger in-phase condition, 2f-in; Triangle marker/rigid line represents two-finger anti-phase condition, 2f-an; Circle marker/dashed line represents four-finger in-phase condition, 4f-in; Triangle marker/dashed line represents four-finger anti-phase condition, 4f-an. Error bars represent the standard deviation.