When adults see an object occlude another object, they typically assume that the occluded object (a) continues to exist behind the occluding object; (b) retains the physical and spatial properties it possessed prior to occlusion; and (c) is subject to the same physical laws as prior to occlusion. Piaget (1954) claimed that infants do not begin to share these assumptions until about 8, 12, and 18 months of age, respectively. Over the past three years, we have conducted an extensive series of experiments designed to investigate Piaget's description of the development of infants' beliefs about occluded objects. The results we have obtained do not support Piaget's description. These results indicate that (a) infants as young as 3 months of age understand that objects continue to exist when occluded; (b) infants as young as 5.5 months of age are aware that objects retain their physical and spatial properties when occluded; and (c) infants as young as 9 months of age make inferences about occluded objects. In general, these findings indicate that young infants' understanding of the physical world is far more advanced than the work of Piaget and his successors had led us to believe.
The first aim of the proposed research is to pursue a number of questions raised by our findings, namely: (1) Are infants less than 5.5 months of age able to represent the properties of occluded objects? (2) How sophisticated are 9-month-old infants at inferring the physical and spatial properties of occluded objects, and are younger infants also capable of making such inferences? Finally, (3) How can one account for the discrepancy between Piaget's conclusions and those suggested by our findings? The second aim of this application is to explore other facets of infants' physical world. Two physical domains will be investigated: (1) infants' understanding of support relations and (2) infants' understanding of collision events. Since our research has revealed that infants' understanding of object permanence is surprisingly sophisticated, it is reasonable to expect that investigations of other aspects of infants' physical world will also bring to light hitherto unsuspected competencies.

National Institute of Health (NIH)
Eunice Kennedy Shriver National Institute of Child Health & Human Development (NICHD)
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Human Development and Aging Subcommittee 3 (HUD)
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University of Illinois Urbana-Champaign
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Baillargeon, Renée; DeJong, Gerald F (2017) Explanation-based learning in infancy. Psychon Bull Rev 24:1511-1526
Setoh, Peipei; Scott, Rose M; Baillargeon, Renée (2016) Two-and-a-half-year-olds succeed at a traditional false-belief task with reduced processing demands. Proc Natl Acad Sci U S A 113:13360-13365
Scott, Rose M; Richman, Joshua C; Baillargeon, Renée (2015) Infants understand deceptive intentions to implant false beliefs about identity: New evidence for early mentalistic reasoning. Cogn Psychol 82:32-56
Song, Hyun-Joo; Baillargeon, Renée; Fisher, Cynthia (2014) The development of infants' use of novel verbal information when reasoning about others' actions. PLoS One 9:e92387
Setoh, Peipei; Wu, Di; Baillargeon, Renee et al. (2013) Young infants have biological expectations about animals. Proc Natl Acad Sci U S A 110:15937-42
Yang, Daniel Y-J; Baillargeon, Renee (2013) Brief report: difficulty in understanding social acting (but not false beliefs) mediates the link between autistic traits and ingroup relationships. J Autism Dev Disord 43:2199-206
Scott, Rose M; Baillargeon, Renée (2013) Do infants really expect agents to act efficiently? A critical test of the rationality principle. Psychol Sci 24:466-74
Sloane, Stephanie; Baillargeon, Renee; Premack, David (2012) Do infants have a sense of fairness? Psychol Sci 23:196-204
Baillargeon, Renée; Stavans, Maayan; Wu, Di et al. (2012) Object Individuation and Physical Reasoning in Infancy: An Integrative Account. Lang Learn Dev 8:4-46
Scott, Rose M; He, Zijing; Baillargeon, Renee et al. (2012) False-belief understanding in 2.5-year-olds: evidence from two novel verbal spontaneous-response tasks. Dev Sci 15:181-93

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