Early interaction is a dynamic, emotional process in which infants influence and are influ­enced by caregivers and peers. This chapter reviews new developments in behavior imag­ing--objective quantification of human action--and computational approaches to the study of early emotional interaction and development. Advances in the automated mea­surement and modeling of human emotional behavior--including objective measurement of facial expressions, machine-learning approaches to detecting interaction and emotion, and electrophysiological measurements of emotional signals--provide new insights into how interaction occurs. Furthermore, advances in automated measurement and modeling can be applied to the study of atypical development, contributing to our understanding of, for example, social affective behaviors in toddlers with autism spectrum disorder (ASD). The chapter concludes by posing questions for future directions of the field of computa­tional approaches to emotion. [This chapter was published in: "The Oxford Handbook of Emotional Development," edited by D. Dukes et al., Oxford University Press, 2022, pp. 305--C21.P102.]