Figure 2.

Calculation of dependent variables. (A,B) Exemplary trial segment showing different movement patterns of two participants. The different peak alignments indicate the different phasing of the two hands. Frequency ratio and relative phase were calculated using methods described in the text. (C) The Euler form of the fast hand's angular displacement, ζ_F(t) = A_F(t)e^iϕ_F(t) where A_F and ϕ_F mean the amplitude and phase in the fast hand. The time series for two and a half cycles of the fast hand angle was taken from (B). (D) Instantaneous phase of both hands' position calculated with Hilbert transform. (E) Instantaneous frequency of slow and fast hand, ω_S and ω_F, calculated as time derivative of phase. Frequency ratio was the ratio of mean ω_F over ω_S (solid lines) in each trial. (F) Calculation of relative phase: phase of slow had ϕ_S multiplied by 3 is subtracted from phase of the fast hand ϕ_F. Mean and standard deviations across one trial served as dependent measures. (G) Exemplary power spectral densities of fast and slow hand in a single trial to illustrate the calculation of crosstalk. Fast hand crosstalk is the ratio of the two peaks in the fast hand (P₂/P₁), where P₁ is the primary peak and P₂ is the spectral power at the movement frequency of the slow hand. (H) Distance between two trajectories (normalized). For visualization purpose, the distance in the 3D space is shown by blue lines between corresponding points on the two trajectories.