‘Laughter is contagious’: Orangutans, the least social of all great apes, value food rewards more when in a good mood, study finds

Orangutans, who are one of the most intelligent primates, may share another habit with humans: their food choices, which depend on their mood, a new study from Indiana University (IU) suggests. It shows that when the great apes heard other orangutans in their group laugh before they searched a bowl for a treat, they were more appreciative of the reward.

Scientists have long agreed that when humans are in a positive mood, it boosts learning and makes the experience more engaging. However, it hasn't been studied in other great ape species.

‘Emotion has important effects on rational thought,’ researcher says

As per Erica Cartmill, a professor of anthropology and cognitive science at Indiana University, who was also part of the work, this study is to find out exactly that, like humans, whether other animals feel the joy of learning new things while they are having a good time.

“One of our big motivations … is building on human research that shows that emotion has important effects on rational thought – and that they aren’t two separate things; they really influence one another,” she said in a statement to The Guardian. “We wanted to extend that to animals – in this case to orangutans.”

Orangutans were given food rewards

Led by Daan Laméris, a postdoctoral researcher at IU, the study, published in Biology Letters in the October 2026 edition, gave orangutans two bowls that contained different materials, and the animals had to dig through to find a food reward inside for five days.

On the first and third day, food was always hidden under one material, like wood chips, and never under the other. For the second and fourth days, the same unrewarded material was given to them, alongside a new material, like yarn pieces with a reward beneath.

Also Read: Orangutans have the longest birth gap among mammals; a 2018 study explains how their 7.6-year wait for another baby, scarce forest fruit and solitary life may actually help them survive

On day five, the researchers presented the orangutans with two bowls, each with a treat buried beneath one of the two food-covering materials. They then asked the orangutans to choose a bowl.

Researchers played sounds of laughing orangutans while they chose food treat

By then, the orangutans had already learned that food treats were hidden under both wood chips and yarn, so they shouldn’t prefer one over the other. Now, in the background, the team had played the sound of laughing orangutans when the great apes were searching in one material, and another sound when the orangutans were searching in a different bowl.

‘Laughter is contagious,’ researchers concluded

When they had a choice between both hiding places, orangutans preferred the material that they dug through when listening to their peers’ laughter.

“Because laughter is contagious for all great ape species, it can impact mood positively,” the university said in a press release published on phy.org. The team of researchers concluded that hearing laughter puts orangutans in a more positive mood, and they value the reward more in that moment.

“It is surprising to find these effects with orangutans, because they are the least social of all the great apes,” Laméris said in the statement, who conducted the majority of the orangutan study at ZOO Planckendael in Mechelen, Belgium. “So even among relatively nonsocial animals, laughter is important.”

“What we've shown in this study is that we can measure the value of laughter, and we can measure how much mood is valued,” Cartmill explained. “When you're in a better mood, the memories you form are remembered more positively and have more value to you.”