First published in 2006. This work represents an attempt to synthesise studies on the development of perception which Piaget started twenty or so years ago, when the Faculte des Sciences de Geneve appointed him to the Chair of Experimental Psychology and Director of the Psychological Laboratory. Most of the studies to be reported have already appeared in the Archives de Psychologie under the general title of Recherches sur Ie Developpement des Perceptions, however, more than fifteen studies which have not been published and which we shall deal with in the following pages.