In this chapter we explore potential discontinuities between animal and human cognition that stem from the unique features of the human brain. Recently evolved modules enable symbolic representation, language, and the understanding of internal states. The term “theory of mind” refers to an abstract causal system that allows one to explain and predict behavior through reference to unobservable mental states such as beliefs, intentions, desires, and emotions. The development of the child’s theory about inner states underlies the increasing complexity of the child’s social cognition and emotional experience.