The social self in the developing brain.

The notion that the self is fundamentally social in nature and develops through social interactions has a long tradition in philosophy, sociology, and psychology. However, to date, the early development of the social self and its brain bases in infancy has received relatively little attention. This presents a review and synthesis of existing neuroimaging research, showing that infants recruit brain systems, involved in self-processing and social cognition in adults, when responding to self-relevant cues during social interactions. Moreover, this review draws on recent research, demonstrating the early developmental emergence and social embeddedness/dependency of the default-mode network in infancy, a brain network considered of critical importance to the sense of self and social cognition. This stands in contrast to research pointing to the relatively late ontogenetic emergence of the conceptual self, by about 18-24 months of age, as seen in the mirror-self recognition test. Based on this review and synthesis, the social self first hypothesis (SSFH) is formulated, presenting an integrated view, arguing for the early ontogenetic emergence of the social self and its brain basis. This developmental account informs and extends existing evolutionary thinking, emphasizing the primary role that social interdependence has played in the evolution of the human mind.