Experimental design
affirmative head nods
A balanced two-by-two factorial between-groups experimental design was used. The two factors were warm facial expression (with/without, i.e. neutral face) and affirmative head nods (with/without). Therefore, participants were randomised to one of four virtual coach conditions: (1) neutral face (2) neutral face and affirmative nods (3) warm facial expressions and (4) warm facial expressions and affirmative nods. In all experimental conditions the virtual coach’s facial expression included basic behaviours such as eye blinking and lip syncing. The study was single-blind. Participants were unaware of the study hypotheses or that they were being randomised to interact with one of the different versions of the virtual coach.We calculated a target sample size for a between-factors ANOVA using 