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This is Scientific American's 60-Second Science. I'm Cynthia Graber. This will just take a minute.

Conscious planning for the future was thought to be a cognitive¹ behavior unique to humans. Not anymore. Researchers in Sweden have found a zoo chimp² that's clearly been making plans. They watched him for a decade and came to an inescapable conclusion. He was stocking up on stones to throw at visitors. The research was published in the March 9 issue of Current Biology.

When the chimp first got to the zoo, he didn't throw many stones. But the few times he did got quite a reaction. And his rate of stone throwing picked up. Researchers swept the chimp’s area and found caches of stones. Then a caretaker hid and watched the chimp collect stones to throw later. Eventually the chimp tapped at concrete structures to break off pieces to throw.

The researchers say this behavior is different from, say, a chimp using a stick to collect termites³ to eat. That could be just meeting an immediate⁴ need. But the stone thrower is clearly and calmly planning ahead. Which means that chimps⁵ probably have an inner⁶ life much as we do. They can review past events and plan for the future. Which probably doesn't include any glass houses.

Thanks for the minute for Scientific American's 60-Second Science. I'm Cynthia Graber.