Infants utilize various communication techniques, including smiles, frowns, looking away, crying, and body movements. Such displays assist parents in understanding their infants' emotions. Moreover, these techniques help infants to control their own affective states in response to external stimuli. For example, an infant's smile in response to a toy communicates to a parent happiness and enjoyment. On the other hand, a frown or turning of the head tells a parent the infant is overwhelmed by the toy or is disinterested.
Parents also communicate through verbalization, facial expressions, and body movements.
Parents and infants synchronize their behavior by learning one another's language and rhythms. Synchrony and symmetry lead to entrainment, the anticipation of one another's responses. As a result, parent and infant develop a set of rules for communication. Turn-taking and compliance to these rules are practiced through repeated play interactions. Finally, flexibility is essential.