He [the child] climbs upstairs and on chairs. He does not climb on chairs in order to sit on them, but just for the sake of climbing. We may wonder why he should make such a great effort if he does not want to enjoy sitting in an armchair once he has got up and into it. But no, he climbs onto the seat of the chair, across the arms and down on the floor again. It is a cycle of activity, an effort which brings a special coordination of movement. His purpose is to train himself and not to enjoy himself.