Children's ability to control the facial expression of laughter and smiling: Knowledge and behaviour

A total of 64 children, aged 7 and 10, watched a clown performing three sketches rated as very funny by the children. Two experimental conditions were created by asking half of the participants to suppress their laughter. Facial expressions were videotaped and analysed with FACS. For both ages, the results show a significant shorter duration (but not a lower frequency) of episodes of laughter and Duchenne smiles, and greater frequency of facial control movements in the suppression compared to the free expression group. The detailed results on individual facial action units used to control amusement expressions suggest hypotheses on the nature of the underlying processes. The participants' explicit knowledge of their control strategies was assessed through standardised interviews. Although behavioural control strategies were reported equally frequently by the two age groups, 10-year-olds verbalised more mental control strategies than 7-year-olds. This theoretically expected difference was not related to the actual ability to control facial expression. This result challenges the commonly held assumption that explicit knowledge of control strategies results in a greater ability to execute such control in ongoing social interactions.