This is for the in vitro (no gradient) dataset. Average growth rate (step length averaged over each movie) is most correlated with S1 oscillation strength and R1 oscillation frequency. No significant results were found for signed or unsigned bearing change (data not shown). The oscillation strength measure was designed to be accurate on narrow bands of frequency, and is known to be affected by large variations in frequency as a result of non-linear scalings in the computed power spectrum . We therefore only considered oscillations with a period under 32 min (frequency over 0.031 min −1).