Crows Reason Like Young Children


Crows and their relatives — ravens, jays, magpies, and rooks — are famous in folklore and myth for their intelligence as well as their enigmatic stare. Current science can explain and provide evidence that suggest crows can think and reason like a young child, a new study finds. Based on Aesop’s fable The Crow and the Pitcher, researchers from the University of Auckland tested New Caledonian crows’ understanding of water displacement and how to use this to solve a problem. In the fable, a crow drops pebbles into a pitcher that is half-filled with water. It continues to drop pebbles until the water level is high enough for the crow to drink. Likewise, the experiment required the crows to do the same to get a reward, which is a piece of meat attached to a floating cork.

Researchers put six New Caledonian crows through six different experiments that involved water displacement. After the birds were given a week of training, they passed four of the tests, which include dropping stones into a water-filled tube rather than a sand-filled one, dropping sinking objects instead of floating ones, dropping things into a tube that has a higher water level than a lower one, and using solid things instead of hollow ones.

However, the crows failed two of the tasks that most young children would normally achieve with reasoning and experimentation. One required an understanding of the width of the tube, and the other required an understanding of hidden cues for a U-shaped tube water displacement problem. Each bird performed the narrow and wide tube experiment 20 times and the crows showed no preference of the narrow tube over the wide tube. Researchers speculated a variety of reasons, including the crows’ inability to perceive width (although not likely because they have excellent vision), a lack of motivation to prefer the narrow tube, and the lack of understanding of depth of the tube. In the U-tube experiment, the crows failed to understand the connection between how the tubes work. Only one of the tubes is connected to a smaller and narrowed tube that contain an out-of-reach piece of food floating on water. By placing stones into that U-shaped tube, the water level in the smaller tube will rise. The other tube has no connection to the narrow tube. While most 8-year-olds could solve this problem with perception and motor feedback, the crows were unable to comprehend why dropping stones in one tube is better than the other. After observing 20 trials, researchers concluded that they most likely attained their reward by chance rather than reasoning.

Crows may have a lesser reasoning ability than most 8-year-olds and may be less likely to win in Are You Smarter Than a Fifth Grader, but among their bird-kin, New Caledonian crows are Einsteins. Given their relatively large brain, complex neurological wiring, and exceptional binocular vision, these crows may give science a better understanding on non-human intelligence and how such intelligence evolved in the animal kingdom. It may even explain the nature of human intelligence and reasoning.

By Nick Ng

Nature Communications

California Academy of Sciences

University of Auckland