Object Permanence

Experiment Background

Jean Piaget (1896–1980), a Swiss psychologist, pioneered the systematic study of cognitive development in children. Through careful observation of his own three infants, he documented the emergence of object permanence during the sensorimotor stage (birth to 2 years). Piaget designed simple hiding tasks to test whether infants would search for objects that were no longer visible. His findings became a cornerstone of developmental psychology, inspiring decades of research — including Renée Baillargeon's groundbreaking violation-of-expectation studies in the 1980s that challenged Piaget's original timeline.

Piaget's Theory

Object permanence — the understanding that objects continue to exist even when unseen — is a foundational concept in developmental psychology. Jean Piaget identified it as a key milestone of the sensorimotor stage (birth to 2 years).

Developmental Milestones

• 1.0-4 months: Tracks moving objects but does not search for hidden ones
• 2.4-8 months: Reaches for partially hidden objects
• 3.8-12 months: Searches for hidden objects, but commits the A-not-B error
• 4.12-18 months: Correctly finds objects after visible displacement
• 5.18-24 months: Understands invisible displacement — object permanence is complete

The A-not-B Error

In the A-not-B task, an object is repeatedly hidden at location A, and the infant retrieves it. Then, in full view of the infant, the object is moved to location B. Despite seeing the displacement, 8–10 month-old infants often reach back to A — the previously rewarded location. This error reveals that early object permanence is fragile: infants rely on motor habits and prior success rather than purely representational reasoning. The error typically disappears around 12 months, coinciding with the maturation of prefrontal cortex circuits supporting working memory and inhibitory control.

Violation of Expectation Paradigm

Renée Baillargeon introduced an alternative method that does not require infants to reach or search. Instead, infants watch possible and impossible events while their looking time is measured. Longer looking at the impossible event implies the infant expected the object to persist — evidence of object permanence. Using this paradigm, Baillargeon (1987) found that infants as young as 3.5 months looked longer at impossible events, suggesting object permanence emerges much earlier than Piaget's manual search tasks indicated. This finding sparked ongoing debate about what manual search tasks truly measure.

References

• Baillargeon, R., Spelke, E. S., & Wasserman, S. (1985). Object permanence in five-month-old infants. Cognition, 20(3), 191-208. 10.1016/0010-0277(85)90008-3
• Piaget, J. (1954). The Construction of Reality in the Child. Basic Books.
• Baillargeon, R. (1987). Object Permanence in 3.5- and 4.5-Month-Old Infants. Developmental Psychology, 23(5), 655-664.