Description:
Summary : How do 5 to 9 month-old infants master the invariant « to be in between » ? Two experiments investigated the child's apprehension of the spatial relationship, « an object is between two other objects », and their detection of the invariance of this relationship over displacements of the objects. 57 infants, aged 4 to 9 months, were presented with objects undergoing three types of movement : two rotations in the horizontal plane (180° and 90°) and a rotation in the vertical plane. These movements were visible in one experiment and invisible in the second one. Only the central object was moveable, and the infants were expected to look at and to grasp that object after the display was moved. The results show that the infants tended to look at the central object, even when they did not grasp it or grasped a different object. Performance varied as a function of conditions, the easiest condition being the 180° rotation, the 90° one being always the most difficult. It is concluded that infants as young as 5 month master the invariant « to be in between » whether the display is visible or not when moved. Key words : spatial invariant, in between relationship, sensori-motor coordination.