Crows are able to complete the Aesop's fable task; the task requires the subject to drop a stone in a glass of water to raise the liquid level and retrieve an object.
The findings suggest that crows understand water displacement at the level of a five to seven year old child, a PLOS news release reported.
Human cognition relies on understand causal relationships between actions, little is known about how well non-human animals understand this concept.
Researchers decided to test out the Aesop's fable task on crows to see how well they understood water displacement. Crows are known for being extremely intelligent, and have even been observed using tools.
The team tested six wild crows after a brief training period; while not every crow succeeded every time, the researchers found the birds displayed "rapid learning."
Each crow completed between four and six water displacement tasks such as: "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," the news release reported.
The crows failed two more difficult tasks that required them to have a full understanding of the width of the tube or "counterintuitive cues for a U-shaped displacement task," the news release reported.
The findings tipped off the researchers that crows most likely understand volume displacement at the rate of a five to seven year old human child.
"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," Sarah Jelbert from University of Auckland said in the news release.
