Orangutans are more likely to choose food linked to the sound of other apes laughing, according to a small study suggesting that an animal's emotional state can directly shape what it learns to value.
Researchers led by Erica Cartmill, a professor of anthropology and cognitive science at Indiana University, studied six captive orangutans across two zoological institutions. As reported in the journal Biology Letters, the team first trained the apes to search for food hidden under materials such as moss or sawdust. Just before presenting the bowls, the scientists played recordings of either orangutans playing and laughing or neutral sounds like the wind, linking each soundtrack to a specific covering material.
On the fifth day, the apes were given a choice between two bowls that both held treats, with each treat buried under one of the two materials. Four of the six orangutans showed a clear preference for the bowl covered in the substance previously paired with laughter. Cartmill suggested that the positive emotional state created by hearing their peers laugh led the apes to assign a higher value to the reward.
Dr Adriano Lameira, an evolutionary psychologist at the University of Warwick who was not involved in the research, noted that hearing others have a good time seemed to prompt the animals to want the same experience. Cartmill noted that the findings could also hold lessons for human education, suggesting that positive emotional states during learning might help explain why people come to value and pursue certain subjects over others.