EARLY MOTOR DEVELOPMENT: BIOLOGICAL AND ENVIRONMENTAL INFLUENCES ACROSS THE FIRST TWO YEARS OF LIFE

Great variability is described in the delay and achievement of motor growth’s milestones, due to the influence of both genetic/inborn and contextual variables (e.g., socioeconomic status, parent-child interactions). According to the differential susceptibility model, specific temperamental traits, such as infant negative emotionality, define the perimeter of environmental effects on child development, limiting or extending parental effects. The principal aim of the present study is to investigate the interdependence of dispositional (child’s negative emotionality) and environmental (maternal depression) factors in determining the motor development's quality across the first two years of children’s life. Using a cross-sectional study, we assessed 299 infants, 0 to 24 months old, and their mothers. Infants’ motor development was assessed with the Peabody Developmental Motor Scales, 3rd Edition; maternal depression was measured using the Center for Epidemiological Studies - Depression, and Negative Emotionality with the Italian Questionnaires for Temperament. Results highlighted that child’s overall motor growth is differently shaped by the interaction of infants’ negative emotionality and maternal depression across time. In particular, infants low in negative emotionality display no effect of depression on motor development. Conversely, infants with high negative emotionality are likely to be affected by maternal depression. Specifically, high maternal depression tends to foster the negative effect of infant’s negativity on motor development across time, while the absence of maternal depression significantly buffers infant’s negative temperament. Taken as a whole, our findings suggest a role of maternal depression and child’s temperament (negative emotionality) in shaping motor development trajectories. It appears that the temperamental trait of negative emotionality constitutes an individual vulnerability for the motor growth only when a child’s environment is unfavorable. Results are in line with the current neurobiological models of child development, where the infants’ inborn disposition of negative emotionality makes them more susceptible to the effects of the relational context.