Monkeys understand trade
And the relative value of goods too!
Check out this clip:
I love that experiment! Even monkeys understand trade.
Moreso, monkeys also get the differences in value between goods! As soon as Monkey #1 realizes he is getting an inferior good (cucumber yuk, grape yum) for the same price, he immediately and forcefully rejects the trade, displaying frustration and anger.
Bravo! What a great experiment!