This book constitutes the refereed proceedings of the Third Workshop on Human Behavior Understanding, HBU 2012, held in Vilamoura, Portugal, in October 2012. The 14 revised papers presented were carefully reviewed and selected from 31 submissions. The papers are organized in topical sections on sensing human behavior; social and affective signals; human-robot interaction; imitation and learning from demonstration.

Speech is the principal supporting medium of language. In this book Pierre-Yves Oudeyer considers how spoken language first emerged. He presents an original and integrated view of the interactions between self-organization and natural selection, reformulates questions about the origins of speech, and puts forward what at first sight appears to be a startling proposal - that speech can be spontaneously generated by the coupling of evolutionarily simple neural structures connecting perception and production. He explores this hypothesis by constructing a computational system to model the effects of linking auditory and vocal motor neural nets. He shows that a population of agents which used holistic and unarticulated vocalizations at the outset are inexorably led to a state in which their vocalizations have become discrete, combinatorial, and categorized in the same way by all group members. Furthermore, the simple syntactic rules that have emerged to regulate the combinations of sounds exhibit the fundamental properties of modern human speech systems. This original and fascinating account will interest all those interested in the evolution of speech.

Oudeyer combines insights from neuroscience, evolutionary biology, and linguistics to explore questions about the origins of speech. He puts forward the startling proposal that speech can be spontaneously generated by the coupling of evolutionarily simple neural structures connecting perception and production. He tests this hypothesis through a computational system and shows that the linking of auditory and vocal motor neural nets produces syntactic rules that exhibit the fundamental properties of modern human speech systems. This fascinating account will interest all those interested in the evolution of speech.