Plotting primates: Monkeys are capable of complex thinking, making careful decisions

PITTSBURGH — Deliberate decision making isn’t reserved solely for homo sapiens after all, according to groundbreaking new research focusing on primates. Researchers from the University of Pittsburgh say we’ve all jumped to the occasional rash decision, but generally speaking, humans have the mental capacity to carefully think over a problem, go over the options, and settle on the best possible decision. Now, these latest findings reveal that monkeys can do the same.

Scientists report that, just like humans, monkeys are capable of complex deliberation and careful decision-making. More specifically, for the first time ever, the study shows monkeys can think deeply about a problem, consider various factors such as costs, consequences and constraints, and ultimately reach an optimal outcome — as opposed to impulsively reaching for the first available option.

“Humans are not the only animals capable of slow and thoughtful deliberation,” says senior author William Stauffer, Ph.D., assistant professor of neurobiology at the University of Pittsburgh School of Medicine, in a media release. “Our work shows that monkeys have a rich mental state that renders them capable of intelligent thinking. It’s a new paradigm for studying the neurophysiological basis for deliberative thought.”

How do humans think about what we want in life?

What happens in our brains when we close our eyes and deliberate over complex questions (who to choose as friends, what to study at school, etc.)? Researchers set out to answer a fundamental question when comparing man with animal: are other animals, including monkeys, capable of the same complexity of thought?

Several decades ago, Nobel Prize laureate Daniel Kahneman, Ph.D., revolutionized the field of behavioral economics with Prospect Theory. In his book, “Thinking Fast and Slow,” he postulated that humans use two distinct systems of thinking: one that is nearly instantaneous and happens automatically (dubbed “fast”), and another that is a much slower form of conscious logical reasoning that requires more mental effort (called “slow”).

Man's brain
(© Prostock-studio –

Slow, effortful thinking, for instance, allows us to write music, develop scientific hypotheses, and balance our checkbooks. Now, this new research suggests slow thinking is not unique to humans.

The team’s approach entailed presenting monkeys with combinatorial optimization problems in what Pitt neuroscientists call the “knapsack task” and rewarding the animals based on the value of the submitted solutions. This revealed that monkeys employed both sophisticated mathematical reasoning and efficient computational algorithms to overcome complex problems.

Notably, both performance and speed of deliberation was dependent on the task’s complexity among monkeys, and solutions closely matched those generated by efficient computer algorithms designed specifically to solve the optimization problem.

“Results from this work will contribute neurophysiological evidence to enlighten centuries of discussions about dual process theories of the mind, the structure of thoughts, and the neurobiological basis of intuition and reasoning,” Prof. Stauffer writes in an accompanying research briefing.

The study is published in the journal Nature Neuroscience.

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