Harvard’s Center on the Developing Child describes serve and return as exchanges between a young child and a responsive adult. A child makes a sound or gesture, and an adult notices and responds. These interactions support developing communication and social abilities.
The Center also emphasizes the conditions caregivers face. Financial strain, health difficulties and isolation can make consistent responsiveness harder. Supporting caregivers belongs alongside encouraging responsive care.
Source
Harvard University, Center on the Developing Child. Serve and return. Developmental science explainer.
how connection develops