Human infants must learn complex skills to interact effectively with parents and other humans, but these social skills emerge at somewhat different ages in different infants. How can we explain this variability? How do infants attend to their social world, and thereby learn routines to interact effectively with other people? This project follows a group of 45 healthy toddlers who have been tested extensively from 3 to 18 months of age on a variety of changing cognitive and emotional responses to social stimuli. The same infants have been observed regularly at home in interactions with their parents. The current project asks how these toddlers' emerging social skills reflect their individual differences in cognition and emotion as infants, and on the different social input provided by their parents. The project focuses on changes in language and imitation skills from 18 to 24 months of age, and the brain dynamics that underlie these skills. The toddlers who were tested and observed starting at 3 months of age will be invited to participate again at 20 to 24 months of age. New sessions will use a unique system at UC San Diego: a Mobile Brain Dynamics (MoBI) facility for recording EEG (electroencephalographic) and body motion-tracking data simultaneously from two people. The project will use this system to record toddlers and parents as they engage in three types of interactions: 1) toddlers following parent's pointing (or line-of-gaze), 2) toddlers reacting to words spoken by parents, and 3) toddlers imitating parents' simple actions. These interactions represent important social achievements for toddlers. Advanced EEG analysis will be performed on electrical potentials measured on toddlers' and parents' scalps. At the same time special cameras will record the positions of their heads and arms. This design will therefore yield a continuous record of changes in the toddlers' and parents' brain electrophysiology (reflecting their thinking and emotional reactions) and body positions as they interact. In addition, toddlers will complete a battery of behavioral and language tests. This project will pioneer a new paradigm for studying the social development of young children, and yield the most complex and complete data available on how early social-attention behaviors relate to early language and imitation, and brain processes underlying these relations. The results will have implications for early childhood education, treatment of developmental disabilities, and parenting practices.
