Baby humans are social creatures who want to engage and will go to great lengths to encourage such engagement [amazing news, right?]
They are also deeply dependent on such engagement. Babies also display a sense of agency–they act deliberately to create social connections and interactions. Check out the below videos of the Still Face Experiment, it’s amazing how purposefully the infants act in trying to reengage the stone-faced adults.
More about the Still Face Experiment here.