Measuring the causal dynamics of facial interaction

The nature of the dynamics of nonverbal interactions is of considerable interest to the study of human communication and future human-computer interaction. Facial expressions constitute an important source of nonverbal social signals. Whereas most studies have focused on the facial expressions of isolated
individuals, the aim of this study is to explore the coupling dynamics of facial expressions in social dyadic interactions. Using a special experimental set-up, the frontal facial dynamics of pairs of socially interacting persons were measured and
analyzed simultaneously. We employ convergent cross mapping, a method originating from dynamical systems theory, to asses the causal coupling of the facial-expression attractor dynamics. The results reveal the presence of bidirectional causal couplings of the facial attractor dynamics concomitant with the
emotional content of the interaction. We conclude that convergent cross mapping yields encouraging results in establishing evidence for causal behavioral interactions.