The senses may function from very early on but the child does not have the ability to interpret the meaning of all this sensory information. This can only be achieved by experience of the world. The important aspect of both seeing and hearing is the ability to recognise and classify the essential characteristics of what is seen and heard. Newly born infants appear to possess some pre-programmed powers of discrimination and preference but on the whole this ability is learned and the distance senses play a major role in this learning. Being presented with the same face at these times will motivate the child to discriminate.
Memory also begins to play a major role.
Very soon discrimination leads to recognition of a specific adult and real smiling, as opposed to the earlier generalised mouth movement, begins to develop. However there is no understanding of the permanence of the object ie that the object continues to exist even when it can'tbe seen. So even for the normal child it takes time for the child's perception of the world to be more than just sensory information but to be linked to a knowledge of the properties of the real world ie develop concepts about the world. Ultimately they will be able to make judgements about the world based on experience. So we see that perception is an ability to understand meaning in the many impressions presented to the senses, and to discriminate and organise these impressions so that they can be remembered and used.