Overall ANOVA time effects (df = 4,66 or 2,44) for changes in physiological parameters across Still-Face Tests and paired t-tests (df = 15 or 22) testing changes from Play to Still-Face episodes 1 and 2.

Note: P = Play episode; SF1 = Still-Face episode 1; SF2 = Still-Face episode 2; TTOT = total respiratory cycle time; VT = tidal volume; RSA = respiratory sinus arrhythmia; logRSA/VTc = logarithm of RSA normalized by VT (logarithm(RSA/VT)+1), adjusted for TTOT; HR = heart rate.†p-level of both t-tests for each index are Bonferroni-adjusted in this subgroup.