Motor activity and spatial proximity: Relationships to infant emotions and maternal postpartum depression

The ability to express emotions is a protective factor for infant development. Despite the multimodal nature of emotion expression, research has mainly focused on facial expressions of emotions. The present study examined motor activity and spatial proximity in relation to positive and negative infant facial expressions and maternal postpartum depression during face-to-face interactions at four months. Video cameras and a motion capture system recorded mother-infant interactions. Repeated measures ANOVAs were conducted to analyze the effect of micro-coded infant positive and negative facial affect and maternal depression diagnosis on automatically extracted measures of motor activity and spatial proximity, including speed of mothers' arm movements (nondepressed = 32; PPD = 16), and infants' arm movements (nondepressed = 29; PPD = 17), and head distance (nondepressed = 45; PPD = 27). Results showed that the speed of infants' arm movements and head distance were greater during negative compared to positive infant affect. Further, the results demonstrated that the speed of PPD mothers' arm movements was slower than the speed of nondepressed mothers' arm movements. In the discussion, it is suggested that increased speed of infant arm movements during negative affect functions to elicit faster caregiving responses, and that increased head distance during negative infant affect functions to decrease the intensity of the interaction. Finally, the slower speed of arm movements in PPD mothers suggests psychomotor retardation, which is proposed to limit these mothers' abilities to engage their infants during the interaction.