Reddy and colleagues, have suggested that primary intersubjectivity is not just essential for social bonding but that it is the source from which all social knowledge and understanding springs
Human infants reciprocally engage with others from the first few weeks of life. By 6–8 weeks old, they make eye contact, smile at, and summon their partner with cooing vocalizations in face-to-face encounters.
Any act of sharing experiences is founded on the communicative capacity that is already displayed by young infants in primary intersubjectivity.
How important positively-toned, rhythmic, exchanges with other humans are for young infants is revealed by how emotionally perturbed they become when their partner abruptly disengages and by the concerted effort they make to reanimate her
I’m of course not the first to say this. ChatGPT found Sharing Experiences in Infancy: From Primary Intersubjectivity to Shared Intentionality which supports key points, e.g. these quotes: