Scientists have proved Aesop’s fable riddle in which a crow drop stones into water to raise the water level to reach a reward.
The New Caledonian crows studied have an understanding level which would rival a 5 to 7-year-old child, according to New Zealand research.
The study is published in the open access journal PLOS ONE by Sarah Jelbert from the University of Auckland and colleagues.
Crows are known for their intelligence and innovation. They also make tools such as prodding sticks and hooks.
Six wild crows were tested after a brief training period for six experiments. These tasks did not test insightful problem solving but were directed at the birds’ understanding of volume displacement.
Crows completed 4 of 6 water displacement tasks including preferentially dropping stones into a water-filled tube instead of a sand-filled tube, dropping sinking objects rather than floating objects, using solid objects rather than hollow objects, and dropping objects into a tube with a high water level rather than a low one.
However, they failed two more challenging tasks, one which required understanding of the width of the tube and one that required understanding of counter-intuitive cues for a U-shaped displacement task.
According to the authors, results indicate crows may possess a sophisticated but incomplete understanding of the causal properties of volume displacement, rivalling that of 5 to 7-year-old children.
Sarah Jelbert says: “These results are striking as they highlight both the strengths and limits of the crows’ understanding. In particular, the crows all failed a task which violated normal causal rules, but they could pass the other tasks, which suggests they were using some level of causal understanding when they were successful.”
Here’s the video:
Video by Sarah Jelbert
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