Psychologists have recently followed the progression of children's play and their involvement in symbolic play, from non-symbolic manipulation to sensorimotor exploration. Among two- and three-year-olds there is presence in the nature of play in the turns. During this period, children transition from self-directed to other-directed forms of play. They also lean into the difference between literal and abstract, among other things. This phase is basically the one in which the symbolic or "pretend" game manifests itself. Even at this stage parents play a small but significant role. In most cases, parents don't even realize that they promote various levels of games that promote a variety of social stereotypes and social norms to children, for better or worse.