Like humans, monkeys also wonder about what might have been, according to a new study by Yale researchers.

HARTFORD, Conn. — Like humans, monkeys also wonder about what might have been, according to a new study by Yale researchers.

The study, to be published Thursday in the journal Neuron, suggests monkeys experience regret and can learn by imagining alternative outcomes to their actions. More important, the researchers said, it could shed light on the physiological activity of human brains when it comes to depression and schizophrenia.

The general assumption has been that animals learn only by their direct experiences, or trial and error. But Daeyeol Lee, a professor of neurobiology at the Yale School of Medicine, said he has had a hunch that animals have the capacity to imagine alternative outcomes without having experienced them.

“When people have regret, they’re thinking about what could have happened; it’s about imagining what could have happened,” said Lee, co-author of the study. “The reason you do this is because it actually broadens the potential for learning tremendously. It seems like such a fundamental question that I would be surprised if it were exclusive to humans.”

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To test the theory, the researchers monitored the brain activity of monkeys as they played a computer simulation of the game “rock, paper, scissors.” The monkeys received large juice rewards for winning a game, a smaller amount of juice if they tied and nothing if they lost. Most of the monkeys, they observed, would pick whichever symbol they would have won with in the previous game. In other words, Lee said, they were able to think abstractly and imagine an alternative outcome.

With brain imaging technology, Lee and his co-researcher, Hiroshi Abe of Yale University’s department of neurobiology, pinpointed the activity in the brain triggered by this kind of thinking, and the different forms that it takes.

Lee said regret takes two forms, both of which take place in parts of the prefrontal cortex. The practical side of regret — where people learn from it — triggers neurons in the dorsolateral prefrontal cortex. The emotional side of regret — where people get sad or angry about what could have been — triggers activity in the orbitofrontal cortex.

Most regret is good, Lee said, because it helps you learn. “Your brain is running this mental simulation about how you could do things differently in the future to get a better outcome.”

But when people obsess over their regrets, it can lead to depression. Knowing the specific neural activity of regret, Lee said, could lead to medications that treat this specific form of depression.

“It’s an important first step,” he said. “If someone has a pathological amount of regret, and you want to ameliorate it some way, you can target those areas. And when you’re testing those drugs, then you know where to look.”

And because the inability to learn from actual and hypothetical outcomes might be a cause of schizophrenia, Lee said the study might also shed some light on how to treat that disorder.