Our ability to see, hear, read, and correctly interpret pre-textual and contextual* information is a brain function independent of I.Q. This ability in the normal population continues to improve (from birth) long past the age that other skills fall off.
This ability allows us to hypothesize the intention and motivation of other people, that is, to be aware of (up to a point of course) the workings of the others mind. That includes the perception of others as having minds, feelings, intentions, motivations, roles, responsibilities, needs.
This allows us to experience empathy, to grasp from this information both what is likely to happen next and what is expected of us in any given situation.
It allows us to formulate an internal social map of which we are a part. It allows us to develop a rational appraisal of cause and effect in our social world. It allows adaptability. New contextual information can be used to modify our internal map.
This ability begins to develop before language. From the moment the infant smiles at mother and mother smiles back.