Research done in many European countries that house large orphanages where there is lack of interaction between children and adults show those children develop slower and learn with greater difficulty. There is a saying that life can be the greatest teacher. Infants instinctively know that they must learn to breathe and take in nutrients to survive. They begin to recognize the correlation between crying and getting their need met. Parents learnt that each cry is a different indicator to their child's needs.
Toddlers increase their knowledge through trial and error.
Experience will remind them if a certain task or situation is enjoyable or not. It is then that they learn when to continue a certain set of experiences to attain a desired objective. For instance, an infant yearns to be mobile. They quickly realize that if they exert a little energy they can move toward a desired result. They practice even in their sleep until they achieve their goal of movement.