ABSTRACT:To a large extent, the human infant is socialized through the acquisition of a specific cognitive mechanism known as theory of mind (ToM), a term which is currently used to explain a related set of intellectual abilities that enable us to understand that others have beliefs, desires, plans, hopes, information, and intentions that may differ from our own. Various neurodevelopmental disorders, such as autism spectrum disorders, attention deficit hyperactivity disorder, developmental language disorders, and schizophrenia, as well as acquired disorders of the right brain (and traumatic brain injury) impair ToM. ToM is a composite function, which involves memory, joint attention, complex perceptual recognition (such as face and gaze processing), language, executive functions (such as tracking of intentions and goals and moral reasoning), emotion processing-recognition, empathy, and imitation. Hence, ToM development is dependent on the maturation of several brain systems and is shaped by parenting, social relations, training, and education; thus, it is an example of the dense interaction that occurs between brain development and (social) environment. (Pediatr Res 69: 101R-108R, 2011) H uman beings continuously make inferences about the psychological states of others. Each of us is constantly analyzing our impressions of others and constructing theories on the basis of the cues and information we receive. This enables us to understand ourselves and others and is a key determinant of self-organization and affect regulation. In addition to "verbal" descriptions of people and observation of their actions, the individual seeks deeper, more psychologically meaningful understandings and attributions in a causal framework to explain and to predict others' behavior on the basis of internal mental states (1). This kind of theory construction that makes up the core of everyday (folk) psychology is known as Theory of Mind (ToM), a term originating from a study of chimpanzee behavior (2), but entails verbal and conceptual abilities.ToM, mindreading in everyday parlance (3), is one of the subcomponents of social cognition, which embraces all the skills required to manage social communication and relationships in humans and nonhumans. It develops on the basis of certain mentalizing mechanisms and cognitive abilities and gives rise to the awareness that others have a mind with various mental states including beliefs, intuitions, plans, emotions, information, desires, and intentions and that these may differ from one's own. Impairment of ToM ability is often seen in children with autism, even in cases with a normal or high level of intelligence and other cognitive abilities (4).ToM develops fully only in human beings; the presence of a rudimentary ToM in some nonhuman primates and other animals is arguable although they can show very complex social behavior (5). The evolution of ToM probably depends on the increased size of the neocortex and increased importance of vision in primates as well as human beings' complex forms of ...