When does the Mind start working?

Parents generally say that about their children that they will not start realizing the significance of things until they reach a certain age. Does that mean that they need to accumulate enough experience before they can start drawing meaningful patterns in their minds and form connections between things as suggested by Hume ?
But, at the same time is this arguments based on to Descarte’s assertion : “I think, so I exist”, which implies that the mind thinks intuitively, about itself, and thereby brings into existence the significance of events around it and the connection between them through reason. Here lies a problem of what precedes which, or a circular tautology. If human minds do not start working until getting or becoming experienced, how are the early experiences registered and translated as the basis for future ?
Part of the problem is however related to the different ways in which the mind can itself be defined. Is the essence of the mind just pure conscious awareness, as suggested by Descartes. Or is it a product of gradual evolution with the passage of time, as it experiences events and reflects upon them, to reach a level of awareness. It is however quite possible, that the mind that Descartes describes is different from the mind that Hume describes when he says, ‘‘All inferences from experience, therefore, are effects of custom, not of reasoning. ”