Many people hate to walk away from a situation they've invested significant time, money or resources on, even if it's hopeless. Those wasted efforts are called'sunk costs' and the more you spend, the more you're likely to keep at it. It turns out our primate cousins act the same way, according to a new study from Georgia State University. Researchers taught dozens of monkeys to play a video game and, rather than starting over on a new level, the animals kept trying to win the same one round. In fact, they spent up to seven times as long as they should have on one round when they would have had a better chance of getting a treat just skipping ahead to the next one.

New research shows that monkeys outperform humans in a test meant to measure cognitive flexibility. The experiment, conducted by a team of psychology researchers at George State University, pitted humans against capuchin and rhesus macaque monkeys. Both groups were asked to interact with a touchscreen computer that featured four squares with different patterns in them. When subjects pressed on the squares in the right sequence, a triangle would appear in place of one of the squares, and when pressed the triangle would produce a reward. For the monkeys, the reward was a banana pellet, and for humans it was either a short audio jingle or a sign of points being tallied up.