Co-regulation of movements during infant feeding.

The process by which infants move from liquid feeding to caregiver-assisted spoon feeding of semi-solid food is quite a dramatic transition. In previous studies, we observed that in the weeks after the introduction to solid food, mother-infant dyads showed increased co-regulation and synchronization of their respective feeding behaviors (e.g. offering food, accepting/refusing, timing). Learning this new way of feeding and eating requires that infants coordinate their position and movements with the complementary position and movements of the caregiver. The present study augments the category-based analysis of this co-regulation by the analysis of coupling in the dyads based on automatically extracted movement data. Previously collected video data from 10 mother-infant dyads were re-analyzed for the purpose of this study. Movement trajectories of mother's hand and infant's face were obtained by applying an automatic movement detection algorithm (TLD, Kalal et al., 2012; for applications to mother-infant interactions see López Pérez et al., 2017). Coordination was assessed by the method of Diagonal Cross Recurrence Profiles (DCRP), which expresses the degree of synchronization at different time lags. Profiles for each dyad from two different occasions --with one visit in the first week of solid feeding and one approximately 4-5 weeks later-- were compared. The results showed that, on average, most synchronization occurred in the first visit at lag 0. In the second visit there was an average delay in synchronization of about 1 s, with leading behavior starting from the infant. This suggests that the coordination was initially closely synchronized and became somewhat looser over time. Possibly, infants have begun to anticipate and guide the feeding movements enacted by the mother. However, our findings underline the idiosyncratic and complex nature of co-regulation of movements during the introduction of solid food. Whereas some dyads showed signs of increased organization, others seemed to disorganize, re-organize, or showed no organization at all. Many (interacting) factors --both individual and contextual-- may be responsible for the observed differences between dyads. Further research is needed to understand why specific synchronization pathways emerge and whether and how these might relate both to later feeding and eating and to the emergent patterns of participation.