The role of the imagination in adult thinking is to go beyond reality and to express generalised laws. The researcher's job is to specify the cultural tools that preschool children use in the development of their imagination. Previous research has identified two main stages in the development of imagination up until the age of six, a third stage at age six to seven, and two main types of imagination. The first stage involves the creation of an idea or image, while the second and third stages involve two different kinds of planning as imagining future actions. The two types of imagination are affective, which functions to protect the "ego" or the self, and cognitive, which functions to develop a representation of the world. While Freud and neo-Freudians researched affective imagination, Piaget studied "cognitive" imagination in the form of the development of symbolic function. Between two and a half and three years of age the imagination divides into cognitive and affective. Children use cognitive imagination when they reproduce actions with substitute objects (for example feeding a doll) and affective imagination when they reproduce their own feelings. Affective imagination leads children to act out fears and conflicts in play, and also to use symbols to represent their negative experiences. In the early stages children can create images from their imagination, but planning is largely absent. In the second stage (from four to five years) creation is combined with staged planning in which children plan a step, review it, plan the next step and so on. This step-by-step planning, often guided by speech, leads to the creation of invented narratives in which events are "threaded" on to each other. In the third stage (from six to seven years), children are able to use forward plans, often verbalised before action as multi-stage narratives. Only about 20% of children develop the full potential of their imagination, and careful education in the preschool years is necessary if all children are to realise their potential.