Scientists are finally cracking the code on how animals experience joy. Researchers from universities across the United States have launched an ambitious project to develop measurable metrics for happiness in animals, marking a significant shift from decades of focusing solely on animal suffering.
The project, informally called the “joy-o-meter,” aims to establish a serious scientific approach to studying positive emotions in creatures ranging from great apes to parrots and dolphins. Erica Cartmill, a cognitive scientist at Indiana University Bloomington, explained that positive emotion in animals has been hugely overlooked. The team has defined joy as an intense, brief, positive emotion triggered by a specific event, such as encountering favorite food or reuniting with a companion.
Testing Joy in Great Apes
The research team began with great apes in 2022, funded by the Templeton World Charity Foundation. Scientists worked with wild chimpanzees at the Fongoli Savanna Chimpanzee Project in Senegal and bonobos at facilities in Belgium, Des Moines, and Florida.
Primatologist Sasha Winkler successfully measured signs of joy using a cognitive bias test with bonobos at the Ape Initiative. She trained four adult bonobos to approach a black box containing a grape and ignore a white box with no treat. After playing recordings of baby bonobo laughter for seven and a half minutes, the bonobos were more optimistic and likely to check out ambiguous gray boxes. The findings were reported in 2025 in Scientific Reports.
Another experiment involved windfall surprises. Researchers showed bonobos a grape, hid it between bins, and repeated this five times. On the sixth round, they revealed 10 grapes hidden between containers. The Jacksonville bonobos responded with hooting sounds called “food peeps” while the Des Moines bonobos nodded their heads. When researchers arranged video calls between bonobos and their keepers, the apes made similar responses to seeing familiar caregivers they had not seen recently.
Parrots That Love Snow
The Templeton Foundation expanded funding to include parrot and dolphin studies in 2024. Ximena Nelson, a behavioral biologist at the University of Canterbury in New Zealand, investigated keas, large intelligent birds found in the mountains of South Island.
Nelson observed keas making snowballs and sledding down ski hut roofs during sunny, snowy weather. Her previous research revealed that keas make playful warble calls that are contagious, similar to human giggle fits. When played to wild keas, the recordings triggered playful responses and tap-dancing behavior.
Working with zoologist Alex Grabham at Willowbank Wildlife Reserve in Christchurch, the team tested captive keas using windfall experiments with peanut butter as the surprise treat. Grabham used infrared cameras to measure body temperature changes around the birds’ eyes and collected fecal samples from playing parrots to analyze hormone levels. Wild kea data confirmed Nelson’s observations, showing the birds were four times more likely to warble when the sun shone.
Dolphin Victory Squeals
Heidi Lyn, a comparative psychologist at the University of South Alabama, leads the dolphin studies. Other researchers have identified a “victory squeal” that dolphins make when catching fish or receiving prizes from trainers, suggesting release of the reward chemical dopamine in the brain.
Lyn’s team observed similar squeals when dolphins received surprise treats like toys or buckets of ice. Preliminary data indicate these squeals may have a social function, with dolphins making bigger or more frequent squeals when trainers also scream with joy or when socializing with other dolphins.
Machine Learning Breakthrough
Researchers from the University of Copenhagen successfully trained a machine learning model to distinguish between positive and negative emotions in seven different ungulate species, including cows, pigs, and wild boars. The model achieved 89.49 percent accuracy by analyzing acoustic patterns of vocalizations. The work, published in iScience, identified key acoustic indicators including changes in duration, energy distribution, fundamental frequency, and amplitude modulation.
Élodie F. Briefer, associate professor at the Department of Biology and last author of the study, stated this breakthrough provides solid evidence that artificial intelligence can decode emotions across multiple species based on vocal patterns. The findings could revolutionize animal welfare, livestock management, and conservation by enabling real-time monitoring of animal emotions.
Understanding how animals express happiness has major implications for improving the lives of captive animals. Sergio Pellis, an ethologist at the University of Lethbridge in Canada, noted that biological markers are important because animals may sometimes fake behaviors. For instance, horses and dogs can look like they are playing while their stress hormone cortisol indicates otherwise.
The research represents a turning point after decades when studying animal feelings was largely taboo, following strict behaviorist traditions in 20th century psychology. Charles Darwin wrote in the late 19th century that lower animals manifestly feel pleasure and pain, happiness and misery, but scientific attention remained focused on negative emotions until recently.
