Measures of coordination.

<p>Mean cross-spectral coherence between (a) instructed and stimulus, (b) non-instructed and stimulus and (c) participants' instructed and non-instructed movements as a function of tracking and congruency.</p

Example movement time series.

<p>Both example time-series exemplify the typical instructed and non-instructed movements of a single participant for a (a) congruent and (b) incongruent trial. For both (a) and (b), the instructed movement was performed in the horizontal (i.e., frontal) dimension. The black line on the right panel reflects the principle eigenvector (<i>v</i>₁) calculated using PCA (see text for more details). Even though the two examples shown in the figure have the same angular direction of deviation, both angular directions were observed in the pool of participants. Furthermore, nearly every participant exhibited some degree of angular deviation in all congruent trials.</p

Experimental setup.

<p>(a) different congruency conditions (instructed participant direction×stimulus direction). (b) Illustration of the two visual tracking conditions and the control condition (horizontal stimulus motion depicted).</p

Performance for synchronized oscillations.

<p>Relative phase (a) and its standard deviation (b) as a function of stimuli combination. <i>Error bars</i> represent standard errors.</p

Within cycles dynamics for synchronized oscillations.

<p>Half-cycle duration expressed as a percentage of movement period (a) and non-linearity (NL) in movement trajectory (b) of the half-cycles <i>To</i> (black) and <i>Away</i> (white) for the different stimulus combinations in slow (left), intermediate (middle) and fast (right) stimulus frequency.</p

Mean autocorrelation functions for synchronized oscillations as a function of stimulus frequency and stimulus combination.

<p><i>Asterisks</i> indicate significant differences from zero for the lag 1 autocorrelation.</p

Averaged normalized limit cycles for the different stimulus combinations as a function of stimulus frequency, with <i>x</i> and representing the position and velocity of wrist pendulum oscillations of participants, respectively.

<p>Averaged normalized limit cycles for the different stimulus combinations as a function of stimulus frequency, with <i>x</i> and representing the position and velocity of wrist pendulum oscillations of participants, respectively.</p

Experimental setup.

<p>Experimental setup.</p

Within and between cycles dynamics in the self-paced condition.

<p>Mean autocorrelation function of periods (a) and mean limit cycle (b) produced by participants. The <i>Asterisk</i> indicates a significant difference from zero for the lag 1 autocorrelation.</p

Example cross-wavelet plots.

<p>Wavelet power of child (top), clinician (middle) and cross-wavelet coherence (bottom) plots for an exemplary interaction. The length of the interaction was 283 s. In the top two plots, the color indicates the degree of spectral energy at different points in time of the interaction (x-axis) and at different time scales (y-axis periods). In the bottom plot, coherence magnitude and relative phase at a given time scale and a point in time are denoted by color and the orientation of the arrow (pointing right: child-clinician inphase whole-body movement coordination; left: child-clinician antiphase whole-body movement coordination; down: child leading by 90°), respectively.</p