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Crows Are Surprisingly Good at Geometry

Crows display an impressive aptitude at distinguishing shapes by using geometric irregularities as a cognitive cue. These crows could even discern quite subtle differences. For the experiment, the crows perched in front of a digital screen that, almost like a video game, displayed progressively more complex combinations of shapes.

First, the crows were taught to peck at a certain shape for a reward. Then they were presented with that same shape among five others—for example, one star shape placed among five moon shapes—and were rewarded if they correctly picked the "outlier."

“Initially [the outlier] was very obvious,” Nieder says. But once the crows appeared to have familiarized themselves with how the “game” worked, Nieder and his team introduced more similar quadrilateral shapes to see if the crows would still be able to identify outliers. “And they could tell us, for instance, if they saw a figure that was just not a square, slightly skewed, among all the other squares,” Nieder says. “They really could do this spontaneously [and] discriminate the outlier shapes based on the geometric differences without us needing them to train them additionally.”

Even when the researchers stopped rewarding them with treats, the crows continued to peck the outliers.