It looks like we're not the only ones who like giving each other presents and helping others out - orangutans do too!
In a recent study, researchers found the apes could learn the value of tokens and were happy to trade them to get bananas for their partners.
But, like lots of us, how much they were willing to give each other depended on how much they received.
It's thought to be the first time this kind of trading system has been seen in any non-human primates.
Researchers at St Andrew's University gave the orangutans three types of tokens - one could be swapped for bananas for itself, one could get bananas for a partner and a third got them nothing.
The name orangutan means person of the forest
They are the largest tree-living mammals
They eat insects, leaves, bark, flowers and fruit.
At first, a female orangutan, Dok, swapped loads of tokens for bananas for her partner Bim, although he wasn't keen on returning the favour.
But as Dok realised, and became less willing to help him out, Bim responded by getting her more bananas until they were giving each other about the same.
Lots of animals and primates help each other out by swapping things or grooming each other.
But Dr Valerie Dufour, who led the research at the Scottish University, said they'd never been any evidence before of animals changing their behaviour in response to how others helped them.
"It's not just humans that calculate about giving," she said. "And it's not just humans who expect to be given something in return when they are co-operative. Orangutans do that too."