Overview
- An international team tested chimpanzees at Uganda’s Ngamba Island Sanctuary using five experiments with hidden food and varying ‘strong’ visual versus ‘weak’ auditory or trace cues.
- The apes typically stuck with an initial choice backed by stronger evidence but switched when later information was stronger, indicating evidence‑based belief revision.
- In complex ‘defeater’ trials, chimpanzees recognized when earlier cues were misleading, such as a picture of food or a stone causing a rattle, and they updated their decisions accordingly.
- Computational analyses ruled out simpler strategies like recency bias, showing that chimp choices aligned with formal models of rational belief updating.
- The peer‑reviewed findings, published October 30 in Science by researchers from UC Berkeley, Utrecht, Portsmouth and St Andrews, will be extended to other primates and to 2–4‑year‑old children to map developmental and evolutionary profiles.