Effects of prior experience on 4.5-month-old infants' object segregation

Adults bring to bear at least three types of object knowledge-configural, experiential, and physical knowledge-when segregating displays. Prior research suggests that young infants lack configural knowledge: they do not expect similar surfaces to belong to the same units and dissimilar surfaces to distinct units. The present research asked whether young infants could make use of another type of object knowledge, experiential knowledge, when organizing displays. In the first experiment, 4.5-month-old infants were familiarized with a stationary display composed of a yellow cylinder lying next to a tall, blue box. In the test events; a gloved hand grasped the cylinder and pulled it a short distance to the side; the box either moved with the cylinder (move-together condition) or remained stationary (move-apart condition). The infants tended to look equally at the move-apart and the move together events, as though they were uncertain whether the cylinder and box constituted one or two units. Subsequent experiments examined whether infants would respond differently to the cylinder-and-box display if they were briefly exposed to the box alone (Experiment 2), or to the cylinder alone (Experiments 3 and 4), prior to seeing the test events. The results indicated that the infants' responses to the cylinder-and-box display were affected by these prior experiences: after seeing the box alone for 5 s, or the cylinder alone for 15 s, the infants looked reliably longer at the move-together than at the move-apart event, suggesting that they now viewed the cylinder and box as separate units and hence were surprised in the move-together event when they moved as one. In a final experiment (Experiment 5), infants were found to be able to use a prior experience with the box to parse the cylinder-and-box display even if this experience took place in a different setting (the infants' homes) and as long as 24 hours before the infants were shown the test events in the laboratory. Together, the present findings provide strong evidence that 4.5-month-old infants, like adults, use their experiential knowledge when segregating displays.