The field of socially intelligent agents (SIA) is a fast growing and increasingly important area that comprises highly active research activities and strongly interdisciplinary approaches. This title emerged from the AAAI Symposium "Socially Intelligent Agents - The Human in the Loop". The book provides 32 chapters, addressing topics such as: social robotics; embodied conversational agents; affective computing; anthropomorphism; narrative and story-telling; social aspects in multi-agent systems; new technologies for education and therapy; and more.