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Oded Ritov @oded-ritov.bsky.social · 30/09/2026

These expectations could be the basic building blocks that evolved into the generalized fairness expectations we see in humans. For more on this thinking, see our BBS commentary, w/ Colin Jacobs and @janengelmann.bsky.social: doi.org/10.1017/S014...

doi.org

Fairness expectations scaffolded the evolution of larger groups | Behavioral and Brain Sciences | Cambridge Core

Fairness expectations scaffolded the evolution of larger groups - Volume 48

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Oded Ritov @oded-ritov.bsky.social · 30/09/2026

This is the first study to show that chimpanzee friendship is not just about prosocial behavior, but also about inhibiting antisocial behavior, and suggests that there may be expectations from both sides of the friendship.

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Oded Ritov @oded-ritov.bsky.social · 30/09/2026

We interpret this through two processes: chimpanzees have higher expectations from their friends, and get angry when these are violated; but are ultimately motivated to maintain their friendship, and therefore inhibit this response.

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Oded Ritov @oded-ritov.bsky.social · 30/09/2026

Thieves stole more often from non-friends than from friends. We also looked at the victims’ emotional response; victims were initially angrier at friends, but dialed down their responses from trial to trial. When non-friends stole from them, they stayed moderately upset throughout.

Two-panel dot-and-whisker plot of chimpanzee victims' predicted negative responses (log scale) across three trials, comparing friend and non-friend thieves. Left panel: full trial. Right panel: 30 seconds after the theft. In both panels, responses toward friends start higher on trial 1 and decline steadily through trial 3, with the drop steeper in the 30-seconds-after-theft panel. Responses toward non-friends stay flat at a moderate level across all three trials.

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Oded Ritov @oded-ritov.bsky.social · 30/09/2026

We had pairs of chimpanzees participate in a task where the “thief” could steal a tray with pieces of pineapple that the “victim” was feeding on. Each victim participated once with their friend, and once with a neutral groupmate.

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Oded Ritov @oded-ritov.bsky.social · 30/09/2026

Do chimpanzees value their friendships enough to pass on juicy pineapple? In our new paper, out now at Evolution and Human Behavior, we find that they do! www.sciencedirect.com/science/arti...

Screenshot of the paper header on ScienceDirect. Evolution and Human Behavior, Volume 47, Issue 6, November 2026, article 106948. Title: "Chimpanzees steal less from their friends and expect them to do the same." Authors: Oded Ritov, Christoph J. Völter, Liran Samuni, Avi Benozio, Dacher Keltner, Jan M. Engelmann, Laura S. Lewis, Esther Herrmann.

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Reposted by Oded Ritov

joshuaconfer.bsky.social @joshuaconfer.bsky.social · 05/02/2026

Why do otherwise rational people disagree about the same evidence? Our new paper finds that group membership is a deeply rooted influence on how we form beliefs, leading even preschoolers to bias their evidential standards and form inaccurate beliefs. www.nature.com/articles/s41...

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