New Caledonian crows are especially clever. Experiments have shown that they are able to make tools and use them, and they’ll even add stones to water to raise the level higher.

Sarah Jelbert, a graduate student in the psychology department at the University of Auckland, worked with the crows in experiments on dropping stones in water. So, she said, she was used to them performing well on tests of thinking ability.

But when she first tried them on something called an A-not-B test, she said, “They were absolutely terrible.”

The test is not that difficult. It’s like a simplified version of the shell game for animals. After putting a treat in one covered bowl that the animal has been trained to expect will hold a treat, a tester takes the treat out, shows it to the animal, and moves it to another bowl.