6- to 8-month-old infants’ understanding of goal-directed actions is unaffected by a mild psychosocial stressor

Sarah Witt, Anna Exner, Sabine Seehagen, Norbert Zmyj

Mild stress is present in infants’ everyday life, but its effect on their cognition is largely unexplored experimentally. The present pre-registered study tested whether stress leads to a shift from a goal-directed to a movement-based interpretation of others’ actions. Eighty-eight infants aged 6–8 months were tested in either a stress or a control condition. Pre- and post-stress levels were assessed via parental rating and salivary cortisol. In a subsequent visual habituation paradigm, infants watched videos of a human hand repeatedly grasping one of two objects. At test, the positions of the objects were reversed and the hand alternately grasped each object. Parental ratings, but not salivary cortisol concentrations indicated a higher stress level in the stress condition compared to the control condition following the manipulation procedure. No statistically significant differences in infants’ looking behavior at test as a function of condition (stress vs. control) were found. Across conditions, infants looked longer to the test trials in which the hand grasped the new object using the old grasping path, indicating that they had habituated to the goal of the action. Additionally, infants in the stress condition tended to look longer at habituation trials than non-stressed infants. These results suggest that acute stress does not influence infants’ interpretation of others’ actions as goal-directed. However, the slower habituation in stressed infants may indicate that identifying the action target was more difficult for them.