From faces to minds: Exploring socio-cognitive development with fNIRS

As the social brain develops, cognitive processes, such as theory of mind, become increasingly sophisticated allowing for more complex social interactions. The human face plays an important role in facilitating natural interactions, allowing for the recognition and interpretation of emotions. In this thesis, I investigated the neural correlates of social cognition with a focus on skills required for social interaction across development. To investigate how important a real human face is during interactions, Chapters 2 and 3 explored brain processing of social interactions with humans versus avatars in both live and pre-recorded online environments. Functional near-infrared spectroscopy (fNIRS) was used to measure neural responses during a social interaction task. In Chapter 2 (adults), there were stronger cortical responses in social brain areas for pre-recorded compared to live social interactions, perhaps reflecting how effortful these types of interactions are to process. Results also suggested that some parts of the brain have increased cortical responses for human compared to avatar faces, and that there was a preference for looking at human eyes during a social interaction. In Chapter 3, I extended the same social interaction paradigm to test a key period for social development: middle childhood (6-11 years). Evoked responses suggested that both how realistic and how live the face was influenced children’s social brain processing, though results were more mixed than in adults. Chapter 4 examined whether responses to emotional faces in infancy as measured with fNIRS were related to their later development of theory of mind (3 years). Exploratory results indicated that in some social brain areas a potential brain-behaviour relationship exists, though there was little evidence to suggest overall cortical responses were related to theory of mind. Taken together, these chapters contribute to the idea that theory of mind is somewhat dependent on the ability to identify a face, process facial expressions and infer emotions or intent of another person during social interactions.