This book constitutes the refereed proceedings of the 4th International Workshop on Human Behavior Understanding, HBU 2013, held in Barcelona, Spain, in October 2013. The 21 papers presented were carefully reviewed and selected from 50 submissions. The papers are grouped in topical sections on: behaviour and affect in arts, creativity, entertainment, and edutainment applications; actions and activities; facial behavior; social signals; and affective signals.
