A theory is presented to explain the perception of partially occluded objects and illusory figures, from both static and kinematic information, in a unified framework. This detailed theory of unit formation accounts for most cases of boundary perception in the absence of local physical specification. (SLD)

In order to help preschool children understand mathematical principles, five different learning activities designed to help them think about physical transformation or change are described. Introductory remarks focus on Piaget's concept of transformation and on various strategies teachers can use to help children consider changes in the state of…

A series of studies focused on (1) the evolution of the notion of identity of objects among infants up to 15 months of age and (2) the changing rules by which this development may be understood. Six identity tasks were presented to 60 infants divided into five age groups: 5, 7, 9, 12, and 15 months. Two objects were used in all tasks. In the first…