Reasoning about containment events in very young infants

The present research examined very young infants' expectations about contai nment events. In Experiment 1, 3.5-month-old infants saw a test event in wh ich an object was lowered inside a container with either a wide opening (op en-container condition) or no opening (closed-container condition) in its t op surface. The infants looked reliably longer at the closed- than at the o pen-container test event, These and baseline data suggested that the infant s recognized that the object could be lowered inside the container with the open but not the closed top. In Experiment 2, 3.5-month-old infants saw a test event in which an object was lowered either behind (behind-container c ondition) or inside (inside-container condition) a container; next, the con tainer was moved forward and to the side, revealing the object behind it. T he infants looked reliably longer at the inside- than at the behind-contain er test event. These and baseline results suggested that the infants in the inside-container condition realized that the object could not pass through the back wall of the container and hence should have moved with it to its new location. Experiments 3 and 3 extended the results of Experiments 1 and 2 to 2.5-month-old infants. Together, the present results indicate that ev en very young infants possess expectations about containment events, The po ssible origins and development of these expectations are discussed in the c ontext of Baillargeon's model (Advances in infancy research 9 (1995) 305, N orwood, NJ: Abler) of infants' acquisition of physical knowledge, and of Sp elke's proposal (Cognition 50 (1994) 431) that, from birth, infants interpr et physical events in accord with a solidity principle, (C) 2001 Elsevier S cience B.V, All rights reserved.