A new study has revealed that crows are as smart as humans, apes and monkeys when it comes to relational thinking.
The study by University of Iowa found that crows also have the brain power to solve higher-order, relational-matching tasks, and they can do so spontaneously.
The study involved two hooded crows that were at least 2 years old. First, the birds were trained and tested to identify items by color, shape and number of single samples, before being placed into a wire mesh cage into which a plastic tray containing three small cups was occasionally inserted.
The sample cup in the middle was covered with a small card on which was pictured a color, shape or number of items. The other two cups were also covered with cards - one that matched the sample and one that did not. During this initial training period, the cup with the matching card contained two mealworms; the crows were rewarded with these food items when they chose the matching card, but they received no food when they chose the other card.
Once the crows have been trained on identity matching-to-sample, the researchers moved to the second phase of the experiment. This time, the birds were assessed with relational matching pairs of items.
The researchers said that they believe that their earlier IMTS (identity matching-to-sample) training is likely to have enabled them to grasp a broadly applicable concept of sameness that could apply to novel two-item samples and test stimuli involving only relational sameness.
The study was published in Current Biology.