They are not renowned for their brainpower, but pigeons may be as smart as monkeys when it comes to arithmetic. Three pigeons were shown a computer screen displaying images with one, two or three shapes and trained to list the shapes in ascending order. To receive a reward of wheat, the birds learned to peck the images in the correct order. Moreover, after they had learned this skill, the birds could perform the task with pairs of images containing anything from one to nine objects. Two rhesus monkeys were the first non-human animals to perform this task in an experiment in 1998. The pigeons are the first non-primates to manage it. "We show they can apply what they have learned with a small set of numbers — from one to three — to numbers they've not seen before," says lead researcher Damian Scarf of the University of Stage in Dunedin, New Zealand. "The learning and applying of abstract numerical rules is not unique to primates." "Their performance was indistinguishable from that of the two rhesus monkeys," adds Scarf. "The machinery required for numerical competence is present in the pigeon brain — a brain much different in structure from our own," says Scarf. "Evidence from non-mammalian vertebrates, such as birds, is particularly valuable for examining the evolutionary history of cognitive processes," says Rosa Regain of the University of Trento in Italy, who in 2010 showed that chicks could count from left to right.