Mother-infant co-regulation during infancy: Developmental changes and influencing factors.

Dyadic interaction is the ecological niche in which early human development occurs and parent-infant co-regulation - the reciprocal adjustment between partners when interacting - is key for the dyadic functioning. Research showed that co-regulation changes with the advancing age; however how this development unfolds and by which variables would be affected is largely ignored. The present study investigated co-regulation longitudinal progression across seven-time points (4, 6, 9, 12, 15, 21 and 24 months of infants' age) while exploring the moderating effects of three infant variables (object manipulation, alternated gaze and shared meanings). The sample included healthy mother-infant dyads (N = 79) interacting for 5' in a context including objects. The interaction was coded by using the Fogel's Relational Coding System that distinguishes three main co-regulation patterns, i.e., unilateral, asymmetrical and symmetrical. Object manipulation, alternated gaze and shared meanings were also observed in the first, middle and final parts of the observational period, respectively. We used multilevel modeling technique to identify the developmental trajectories of each co-regulation pattern; we also analyzed whether the trends were moderated by specific factors at specific time periods. Results were statistically significant in both cases. We found an acceleration effect of the age on all the three co-regulation patterns. To specify, asymmetrical pattern decreased very soon, unilateral increased sharply from 6 to 9 months and then declined, symmetrical increased in the 12-15 months period and jumping up at the end. We also found a moderating effect of all the three infant's variables: infants who were higher in object manipulation increased unilateral pattern earlier and more than lower infants; infants who were higher in alternating the gaze between mother and object and in sharing meanings showed a higher and steeper trend of symmetrical pattern. This study is the first shaping co-regulation changes in their form and rate, so reliably accounting for the developmental nature of this process. It also showed that co-regulation changes related to different age dependent skills, thus contributing to define this process as a complex phenomenon.