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Why Trust Matters: The Moral of the “Eye-Poking” Capuchin Monkey

Ulrich Boser 4

When political scientists talk about the importance of trust, they often reach for the literary stars. They pull out the big metaphors. They add some purple to their prose. Researcher Eric Uslaner once called social trust the “chicken soup” of social life. Sociologist Pamela Paxton has argued that trust is “the magic ingredient that makes social life possible.” One German academic was Teutonically blunt, declaring that “a complete absence of trust would prevent [one] even getting up in the morning.”

Despite the florid writing—and the extensive research behind the basic idea—we continue to undervalue the importance of trust. We don’t do enough to support our faith in others. I have a book coming out on social trust in September titled The Leap: The Science of Trust and Why It Matters, and for me, one of the best ways to think about the importance of trust is to consider capuchin monkeys. The small primates live in Central America, and they often work together. When the capuchins chase squirrels, for instance, the monkeys will often go after the babies, with one capuchin distracting the mother while its partner reaches into the nest to swipe one of the children. After netting their prey, the monkeys will eat the squirrel together, making sure to share their haul with each other.

So how do the animals create a sense of trust? How do they know if another monkey is trustworthy? In his wonderful book The Age of Empathy, primatologist Frans de Waal discusses recent research on the monkeys by University of California, Los Angeles’s Susan Perry, and it turns out that one capuchin monkey will sometimes stick his finger inside the eyelid of another capuchin and then hold his finger there for a while. I called Susan Perry to find out more, and for the monkeys, the experience seems just as odd as it sounds. One monkey will slide his finger into another monkey’s eye socket, and then the pair of animals will sit there with a “zen-like look,” Perry told me.

In his book The Age of Empathyde Waal argues that researchers don’t know why the animals engage in “eyeball poking,” but he suggests that it might all about building trust, that the monkeys use the behavior as a way to create faith in each other. Or think of it this way: If one capuchin knows that another capuchin won’t rip out his eye out during a session of “eye poking,” then that capuchin is a monkey to work with in the future.

In other words, “eye poking” seems like a capuchin version of the so-called “trust fall,” as de Waal points out. “Perhaps capuchin monkeys,” de Waal writes, “are trying to find out how much they really like each other, which may then help them decide who can be trusted to support them during confrontations within the group.”

What’s striking, as de Waal suggests, is that the monkeys are willing to risk so much to find out who is trustworthy. Would you want a dirty finger in your eye socket? Would you be willing to risk your eyesight to figure out if you could work with someone or not?

In the end, my point is that if you ever find yourself wondering just how much trust matters, don’t go looking for the answer in purplish prose. Instead, hit play on this video from Susan Perry’s capuchin research and watch just how much a monkey is willing to gamble in order to gain some sense of trust.

Photo credit: Geoff Gallice via Flickr

  1. Ruth Ruth

    Looking forward to the book so that I can read the whole thing

  2. bill bill

    Trust, an eye socket for an eye socket. Fascinating and counter intuitive.
    Amazing, Ulrich. I’ve been with you since your days of writing about goings on at Mrs. Gardner’s palace.
    there’s a story about a man who lost his wallet outside. He was circling around and around a lamppost. A friend asked him where he thought he may have lost his wallet. he pointed to a spot about twenty yards away. He was asked why he didn’t look over there,
    his reply – “the light’s so much better here!

  3. David David

    I tried this once in college. My roommate may have been trustworthy, but he had some rough cuticles.

  4. Bianca Bianca

    No ways I’m trusting my eye balls with a cappuchin. Had enough eye licks already

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