In a non-verbal experiment, each participating baby, 56 in all, sat on a parent's lap and faced an actor (a university student). On the table between the baby and the actor was a toy watermelon slice and two boxes whose openings faced each other; one box was green, the other yellow.
To start, the actor picked up the watermelon slice, played with it, and then hid it in the green box. On subsequent trials, the actor always reached into the green box, as though to grasp the watermelon slice she had hidden there.
Then, seemingly unbeknownst to the actor but in sight of the infant, the watermelon slice moved to the yellow box.
This change created a false belief for the actor as to the location of the coveted watermelon slice, said principal investigator Renee Baillargeon (pronounced BY-uhr-zhan), a professor of psychology at Illinois.
The infants expected the actor to search for the watermelon toy in the green box (where she falsely believed it to be), and not in the yellow box (where it actually was and where the infants knew it to be). The infants looked reliably longer when the actor searched the yellow box, as though surprised by this unexpected event.
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