- Objectives The importance of mother-child interaction in early infancy on child development has been well documented. The purpose of this study was to assess the feasibility of using the Still Face Paradigm to measure mother interactive style, infant affect and emotional regulation in a rural Ecuador setting. Methods Infant's emotional regulation and the quality of mother's interaction were measured with the Still Face Paradigm at 4 months of age (±15 days). Twenty-four infants and their mothers were assessed in their home. Mother interactive style was coded for attention seeking and contingent responding. Emotional regulation was described by change in infant affect between Still Face episodes. Results A significant difference was found for infant affect between the five Still Face episodes (F1,118 = 9.185, p = 0.003). A significant negative correlation was found for infant affect between episode 3 and 2 with attention seeking mother interactive style during episode 3 (rho = -0.44, p = 0.03), indicating that mothers using more contingent-responding interactions had infants with more positive affect. Conversely, a significant positive association was found for infant affect between episode 3 and 2 and contingent responding mother interactive style during episode 3 (rho = 0.46, p = 0.02), indicating that mothers who used more attention seeking play had infants who showed less positive affect. Conclusion for Practice Study results demonstrate feasibility in using the Still Face Paradigm in working populations residing in a rural region in Ecuadorian highlands and may be feasible in other similar populations in Latin America, and as a successful approach to measuring maternal-child interactions within a field-based epidemiological study design.