Crows have long been considered to be the one of the smartest bird species out there, along with other members of the corvid family. New research now equates a crow’s level of intelligence to that of a 5-6 year old human child.
Research published in PLOS ONE by Sarah Jelbert from University of Auckland and colleagues used a technique called Aesop’s fable riddle, in which subjects drop stones into a water container in order to raise its level and receive a reward. Understanding this causal relationship is a key feature of human cognition yet it is not well understood in non-human animals.
New Celadonian crows are known for their intelligence and innovation, as they are the only non-primate species to be able to make tools, such as prodding sticks and hooks. Six wild crows were tested after a brief training period for six experiments. The authors have noted a rapid learning curve displayed by the crows although not all crows successfully completed the experiments.
Scientists were keen to stress Aesop’s fable didn’t test insightful problem solving but instead, tested the bird’s understanding of water displacement. The crows completed four of the six experiments successfully, including dropping stones into a water filled tube instead of a sand filled tube, dropping sinking objects rather than floating objects, and dropping objects into a tube with a high water level compared to one with a low water level.
Two more challenging tasks were not completed successfully. These tests were one that required understanding the width of the tube and one that required understanding of counterintuitive cues from a U-shaped displacement task.
Researchers claimed that these failures of the two more challenging tasks indicate that even though the crows possess sophisticated problem solving ability, it is incomplete. This incompleteness is displayed in human children around the five to six year old age range.
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.”