When Carel van Schaik reached the top of his rope ladder, his first thought was: “Oh shit, there’s an orangutan here.”

He was trying to measure the climate in the canopy of the Sumatran rain forest, using sensors that he had hoisted into the treetops. The devices were incredibly delicate: “You’d touch them and they’d break,” van Schaik recalls. So when he saw an orangutan ambling around, he feared the worst.

Fortunately, the animal was completely uninterested in the equipment. Van Schaik was surprised. It didn’t jibe with the behavior he saw in rehabilitation centers, where orangutans are rescued or confiscated from smugglers, and cared for in captivity. There, the apes were a curious lot, and would fish through garbage cans, raid stockrooms, and even steal laundry from lines. “The wild ones never did that,” van Schaik says.

He and his team at the University of Zurich have spent several years confirming that observation in dozens of individuals. They’ve shown that wild orangutans are decidedly incurious. They eschew the new. They abhor the unfamiliar. Captive orangutans couldn’t be more different. They readily explore what their wild counterparts ignore. Something about captivity, whether it’s the close contact with humans or the absence of predators, unlocks a latent capacity for curiosity. And if that happens early enough, it boosts their problem-solving abilities as adults. “This dormant potential lies there waiting to be used,” van Schaik says.

To test orangutans, one of van Schaik’s team members, Sofia Forss, built fake orangutan nests in the Sumatran canopy. She then filled them with items that the apes would never have seen before—a Swiss flag, plastic fruit, and even an orangutan doll. Footage from motion-sensitive cameras revealed that wild orangutans walked around the items for months. Only two adolescents ever actually touched the unfamiliar items. When another team member, Caroline Schuppli, repeated the same experiment in several zoos, she got completely different results. Within minutes, the orangutans had wrecked the nests.

Meanwhile, Laura Damerius did a similar experiment with 61 orangutans who lived in Indonesian rehabilitation stations, assessing their responses to unfamiliar objects like a human stranger or a lump of purple-dyed food. She found that apes who had spent more time with humans before arriving at the stations behaved more curiously—that is, they actively sought out new things, and explored them with gusto. And this, she found, influenced their mental abilities. On a battery of challenges designed to test their problem-solving skills, the curious orangutans scored higher than their incurious peers.

Scientists rarely study curiosity in other animals, and perhaps for good reason. It’s “a difficult concept to define, even for humans,” says Jill Pruetz from Texas State University, “but it has very intriguing implications for understanding human evolution.”

For example, our ancestors had developed large brains, upright bodies, and basic tools hundreds of thousands of years before they acquired language, art, and other more sophisticated cultural innovations. “We’ve always wondered what unleashed that, and it may have something to do with curiosity,” says van Schaik. Perhaps some change in our society, whether larger groups or the advent of new weapons, afforded us the safety that zoos provide to orangutans. That, in turn, could have unlocked the latent curiosity in our own minds, turning us into explorers and innovators.

Of course, “it’s very hard to test this,” van Schaik says. But orangutans provide some support for the idea. Wild ones learn almost all of their skills by copying their mothers and selected role models. “They’re not going around like Curious George and turning everything over,” says van Schaik. That makes sense. Curiosity, as they say, kills the orangutan. In a world of strangers and dangers, it’s more efficient and less risky to take your cues from experienced peers.

But this means that wild orangutans are conservative animals that only innovate by accident. They try something routine, it has unexpected consequences, they keep on doing that, and other orangutans copy them. “They’re not focused on innovation at all,” says van Schaik. Over decades of studying these animals, he’s seen very few examples of entirely new behaviors.

The same isn’t true for captive orangutans. One group, which was housed on an island in the middle of a river, invented 18 new ways of getting water or extracting items from it, resulting in this famous photo of an orangutan appearing to fish with a stick. Most of these behaviors had never been seen in the wild, and were unusual for a species that normally avoids flowing water.

Other researchers have found similar signs of heightened problem-solving skills in captive hyenas, birds, monkeys, and other animals. Together, these discoveries challenge the stereotypical impression of zoos as stultifying places, where animals are shadows of their fully realized wild selves. Instead, captive animals can sometimes gain skills that their free-living counterparts never acquire.

Why? In captivity, orangutans experience a safe and stable environment, without the constant distractions of hunger and predators. That gives them the time and opportunity to explore, and such explorations, far from leading to a sticky end, are actively rewarded with food and other treats. They also encounter humans, who become trusted role models in the way that the orangutans’ parents do in the wild. And humans ... we like to touch stuff. “Everything we touch becomes ... we call it ‘blessed,’” says van Schaik. “It’s labeled as explorable.”

“Exploration is a building block of play,” adds Jessica Mayhew from Central Washington University, and “play might aid in the acquisition, practice, and fine-tuning of the cognitive tool kit.” Perhaps that’s partly why the more curious individuals are smarter than the average orangutan. “At these rehabilitation stations, individuals are immensely variable in their problem-solving skills,” says van Schaik. “If you’re curious over a long period of time, you accumulate a lot more experience and learn many new tricks.”

Again, there are parallels with humans. Allison Kaufman from the University of Connecticut says that the qualities that van Schaik bundles into “curiosity” are very similar to what psychologists called “openness to experience.” This is one of the so-called Big Five personality traits, and it’s strongly correlated with creativity. And as in orangutans, human creativity only flourishes in the right environment. “It is hard to create without proper tools, time, and safety,” says Kaufman.

I myself am very curious about how urbanization may be influencing the expression of curiosity in animals that are living in cities,” says Sarah Benson-Amram from the University of Wyoming. Urban animals are certainly free-living, but they often experience many of the same conditions—plentiful food, fewer predators, and abundant human role models—that captive orangutans do. Do they become curiouser and curiouser for it?