By now, we all know that being called a "birdbrain" isn’t really an insult; birds have been shown to have several higher-order cognitive skills that we previously thought only primates had the brains for. Jays are capable of episodic memory, parrots can solve multi-step puzzles and use a succession of tools to get a food item, and crows have even learned to use city traffic and stoplights to their advantage. Now, Science reports yet another cognitive area where birds are on par with primates: they have a sense of numbers.

In 1998, a pair of researchers used a novel experiment to show that rhesus monkeys had numerical competence; in other words, they could use abstract numerical rules. The monkeys were shown a set of three images picturing one, two, and three items, and were trained to choose these images in ascending order. Once they had been trained to a certain accuracy level, they were shown numbers of items that they hadn’t necessarily seen before. The monkeys were generally able to choose the greater of the two numbers, even when they didn’t have experience with the values involved. Clearly, they had learned not only the values they were trained on, but also more abstract rules about numerosity.

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