Facial EMG
REGRESSION
EMG data were pre-processed in MATLAB, partly using the EEGLAB toolbox (Delorme and Makeig To investigate if facial mimicry occurred and was modulated by the drugs, we conducted frequentist statistics on the log EMG data by fitting a separate LMM per muscle with the fixed effects emotion (HappyToAngry, AngryToHappy), drug (amisulpride, naltrexone, placebo), and time (5 windows of 1 s), and with random intercepts by subject and stimulus-face, and with by-subject random slopes for emotion, time, and their interaction. These frequentist LMMs were followed up by Bayesian statistics that also modelled an asymptotic regression to account for the non-linear muscle activation/relaxation changes over time in each trial.