Monkeys Playing Video Games Experience 'Sunk Costs' Just Like Humans

Monkeys spent seven times longer trying to beat a level rather than just giving up and moving on.
Derya Ozdemir

You might not be familiar with the "sunk costs" phenomenon, but chances are you've performed actions that go right along with it, such as sticking with a project or a relationship that is going nowhere.

The more time, money, or resources you invest in a situation, the more you're likely to keep it; this phenomenon is so common that these wasted efforts have been called "sunk costs." Now, a new study from Georgia State University has shown that monkeys act this same, potentially self-defeating, way.

Monkeys played a simple video game

Conducted by Julia Watzek, a recent Georgia State University Ph.D. recipient, and her graduate advisor Professor Sarah F. Brosnan, the study had 26 capuchin monkeys and 7 rhesus macaques playing a simple video game where they operated a joystick and. The monkeys needed to move a cursor onto a moving target and keep it there while the target kept moving.

It was seen that, rather than starting over on a new level and moving along, the monkeys kept trying to win the same one over and over again, both species showing sunk cost effects. "They persisted 5 to 7 times longer than was optimal," said Brosnan, "and the longer they had already tried, the more likely they were to complete the entire task."

The study gives insight into how brain works

According to Watzek, studying this phenomenon in animals "teaches us something about how their minds work, as well as our own." 

"The epitome of the sunk cost is I’ve invested so much in this, I’m just going to keep going,” Brosnan said. While sometimes there might be benefits such as patience helping "when you’re foraging for food, hunting prey, waiting for eggs to hatch, seeking a mate, or building a nest or enclosure," there could be some negatives too.


"We’re predisposed to keep trying," Brosnan explained. "And when we find ourselves sticking with things, we should also be a little reflective. Do I have a good reason to keep trying? Or should I leave with no reward, because it will save me more in the long run? That’s really hard to do. But hopefully, we can use our cognitive abilities to help us overcome the emotional heartache of occasional sunk costs."

The new study, "Capuchin and rhesus monkeys show sunk cost effects in a psychomotor task," was published in Nature’s Scientific Reports.

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