How do infants come to understand social interactions between other people? The first objective of the current project is to examine when infants recognize the joint and individual goals that underlie others' social interactions. This will be achieved with a developmental study using eye tracking to examine infants' expectations of others' behavior in social situations. The second objective of the project is to explore the role of both specific and general social experience in the development of social interaction understanding. To do so, a second study will compare infants' understanding of a social interaction between others in an eye tracking task to two types of social experience: their specific experience in a similar social interaction and their general quality of social experience (as indexed by their caregiver relationship quality).The research training objectives that will be achieved during the fellowship include developing and expanding the fellow's skills in research methods including eye tracking and infant behavioral and observational paradigms, and in data analysis methods, including computer programming. Additional complimentary skills will be gained in areas such as management, mentoring, and dissemination of findings.