There is no specific age at which to start using positive reinforcement; children learn to relate reinforcers to their behavior after several similar experiences and patterns. Good deeds that were reinforced at an early age become part of the child’s personality.
As children grow, their needs will differ in the same way that our expectations of them will expand. So, the reinforcers may change, but the general principle remains. The success of positive reinforcement greatly depends not on the child, but on the adult using it as a disciplinary approach.
When used successfully, positive reinforcement can develop a child’s intrinsic motivation. It can provide children some understanding of expectations and behavior.