Haun, D. | bioRxiv Science

bioRxiv2026

Expecting the unexpected: Great apes anticipate surprise in others

Humans adeptly navigate complex social environments by attempting to anticipate the actions and emotional responses of others. Although our closest ape relatives have sophisticated social cognitive abilities, we do not know whether they have a cognitive understanding of others' emotions. For the epistemic emotion surprise, a cognitive understanding would require sensitivity to an agent's belief, to reality, and to any misalignment between the two, allowing one to model the mental conditions that drive surprise. In a non-invasive eye tracking study with 31 chimpanzees and bonobos, apes showed evidence of a cognitive understanding of surprise: they detected the misalignment between an agent's belief and reality, exhibiting greater pupil dilation right before an agent encountered an unexpected outcome relative to an expected one. This suggests that apes and humans share a more complex understanding of others' mental lives than previously thought, capacities that likely evolved millions of years ago in a common ancestor.

animal behavior and cognition↗

bioRxiv2024

The development of social attention in orangutans: comparing peering behaviour in wild and zoo-housed individuals

Social learning is the cornerstone of all cultural processes and plays a pivotal role during the evolution of cognition. To understand how social learning evolved, we have to look at the immediate and developmental conditions affecting individuals tendencies to attend to social information. We compared peering behaviour (i.e., close-range and sustained observation of the activities of conspecifics) in wild and zoo-housed immature Sumatran orangutans (Pongo abelii) by analysing long-term data which included 3101 peering events collected at the Suaq Balimbing research site in Indonesia and at four European zoos on 35 immature individuals. Using Generalized-Additive-Mixed-Models, we tested for age-specific patterns in peering frequency, target, and context selection. We found similar age trajectories of peering in both settings but higher mean frequencies of peering in the zoos, even after controlling for varying social opportunities to peer. Wild immatures preferably peered at their mothers but zoo-housed immatures at non-mother individuals. In both settings, immatures preferred to peer at older individuals, and in learning-intense contexts. Our findings suggest a hard-wired component in the tendency to attend to social information and a considerable degree of ontogenetic plasticity - a combination that was likely foundational for the evolution of complex cultures, including human culture. HighlightsO_LIWe compared attendance to social information in wild and zoo-housed orangutans C_LIO_LIImmature orangutans peer in contexts where learning is expected C_LIO_LIPeering frequency develops similarly over age, suggesting hardwired propensities C_LIO_LIPeering target and context selection differs between the two settings C_LIO_LIOrangutans tendency to attend to social information shows plasticity C_LI

animal behavior and cognition↗