ABSTRACT
Every object of knowledge is situated in time: the idea that occurs to me; the flower or building that meets my gaze; the telling experience I recall to mind. All these things are situated at a precise point in time, are characterized by a certain duration and are ordered within a sequence of events. The study of cognitive psychology cannot therefore afford to ignore the question of the fourth dimension. Indeed, a whole series of studies which I shall describe later has been devoted to investigating the way children conceptualize temporal notions, reason about time or measure events using temporal units.
