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 that required understanding of the width of the tube, and one that required understanding of counterintuitive 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 5-7 year old children.
Sarah Jelbert added, “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.”
It may well be significant that an ancient Greek tale, an Aesop’s fable from about 2500 ya, portrays a crow doing this very thing, raising the possibility that it is an old practice among crows and not exclusively the result of causal reasoning on the part of intelligent individuals. If they didn’t understand the importance of the width of the tube, for example, causal reasoning is not driving the process, or not exclusively.
We have a ways to go with understanding animal thinking patterns and comparisons with 5 to 7 year old children* create lots of headlines without advancing understanding.
* Children usually learn the tasks of daily living starting around two to four, by imitation, instruction, and exhortation. They apply causal reasoning later. Causal reasoning is not always needed to learn a task; it is, however, often needed to analyze a new task in order to decide which techniques to adapt from one task to another. That’s precisely the point at which much animal cognition fails. The technique is learned, but not abstracted as a general principle, thus it cannot be developed beyond a certain point.
Here’s the abstract:
Understanding causal regularities in the world is a key feature of human cognition. However, the extent to which non-human animals are capable of causal understanding is not well understood. Here, we used the Aesop’s fable paradigm – in which subjects drop stones into water to raise the water level and obtain an out of reach reward – to assess New Caledonian crows’ causal understanding of water displacement. We found that crows preferentially dropped stones into a water-filled tube instead of a sand-filled tube; they dropped sinking objects rather than floating objects; solid objects rather than hollow objects, and they dropped objects into a tube with a high water level rather than a low one. However, they failed two more challenging tasks which required them to attend to the width of the tube, and to counter-intuitive causal cues in a U-shaped apparatus. Our results indicate that New Caledonian crows possess a sophisticated, but incomplete, understanding of the causal properties of displacement, rivalling that of 5–7 year old children. – Sarah A. Jelbert, Alex H. Taylor, Lucy G. Cheke, Nicola S. Clayton, Russell D. Gray. Using the Aesop’s Fable Paradigm to Investigate Causal Understanding of Water Displacement by New Caledonian Crows. PLoS ONE, 2014; 9 (3): e92895 DOI: 10.1371/journal.pone.0092895
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