Six zoo orangutans learned that treats were buried under two different materials, such as wood chips and yarn. The rewards were identical. Yet when the apes later had to choose between those two hiding places, every one of them leaned toward the material they had learned about right after listening to recordings of other orangutans laughing and playing.
The study, published Oct. 21 in Biology Letters by researchers at Indiana University Bloomington, suggests that the sounds of other apes having fun can shape how a reward is remembered and valued. The team argues that the laughter likely put the orangutans in a better mood, and that the mood carried over into what they learned.
