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Science Study Finds Chimpanzees Weigh Evidence and Revise Beliefs

Experiments at Uganda’s Ngamba Island used graded cues to test whether the apes update choices when stronger or undermining information appears.

Overview

  • The peer-reviewed paper, led by Hanna Schleihauf with co-authors including Emily Sanford and Jan Engelmann, was published October 30 in Science (DOI: 10.1126/science.adq5229).
  • Across five controlled box-and-treat experiments, chimpanzees favored stronger visual evidence over weaker auditory or trace cues and identified when information was genuinely new rather than redundant.
  • In the most demanding test, so-called defeaters revealed earlier cues could be misleading, and the chimpanzees more often abandoned prior beliefs in favor of more reliable signals.
  • Computational modeling supported the interpretation of rational belief revision and ruled out simpler strategies such as always choosing the latest or most salient cue.
  • Data collection with 2- to 4-year-old children is underway and researchers plan tests in other primates, with authors noting sanctuary-based samples and task specificity mean broader replication is still needed.