Thesis (Ph.D.) - Indiana University, Department of Psychological and Brain Sciences/University Graduate School, 2019Successful social interactions require the coupling of the bodies and minds of the participants. Joint visual attention to the same target is a critical component of this coupling. By 9 months of age, as measured both in trial-based experiments and in continuous naturalistic play, infants engage in joint attention with an adult. Infants’ early joint attention skills, measured in both contexts, are strong predictors of future developmental outcomes including language development. Thus, the consensus assumption is that shared skill sets support joint attention in trial-based experiments and in free play with a social partner. Growing evidence raises doubts about this assumption since the different contexts for joint attention appear to elicit the phenomenon differently. Research is needed to fully understand the phenomenon across contexts and determine whether individual differences in trial-based joint attention are predictive of individual differences in free play with the parent. Furthermore, research is needed to examine joint attention moment-to-moment during play in order to examine the real world infant and parent behaviors that occur during these moments of parent-infant coupling and can point to mechanisms that can potentially link joint attention to infant learning and development. The previous studies that show early joint attention predicts later language development show correlational evidence that the coupling of infants with mature social partners matters for development, and thus the specific pathways through which joint attention benefits infant learning and development are not known. The aims of the dissertation are 1) to understand how joint attention between infants and social partners is achieved in discrete trial-based and free play vi contexts, and whether individual differences in the contexts are related, and 2) to examine the developmental consequences of joint attention in the context of free play in order to begin building a pathway between joint attention and infant learning and development. Together, three studies show that coordinated visual attention occurring during continuous naturalistic parentinfant play supports the infant’s own control of visual attention both in-the-moment and eight months later, but that measures of joint attention obtained during naturalistic play do not tap the same underlying processes measured in trial-based contexts for joint attention. I discuss implications of this work for the theoretical claims on joint attention and suggest a likely pathway through which joint attention achieved in the context of free play with the parent may support language learning as well as academic achievement and self-regulation. The results demonstrate one instance of the larger and general problem in science: when clean and controlled findings in the laboratory fail to translate to the complexity of real-world life.