Orangutans prefer food associated with laughter

Researchers wanted to know if positive emotions change how orangutans form memories. To find out, they trained orangutans to dig through bowls of material (like shredded paper or yarn) to uncover hidden treats. Importantly, the orangutans learned that treats were hidden under both materials, so they shouldn’t prefer one over the other.

Once the apes understood the task, the researchers could test the theory. Before searching through one material, orangutans listened to five minutes of recorded play-laughter from other orangutans. Before digging through a second material, they heard neutral noise, like wind. The reward hidden underneath both materials was identical.

The next day, the orangutans were given a choice between both materials. They overwhelmingly chose the material they had explored while listening to play-laughter. This suggests that hearing their peers play put them in a positive emotional state, causing them to view that specific experience (and the material) as far more valuable.

Importantly, laughter didn’t make the orangutans learn faster. Rather, it changed how they remembered reward value. This shows emotional contagion at work. It’s especially surprising because orangutans are the most solitary apes. Yet even for them, positive social cues shape memory, proving that mood influences how animals process the world around them.