Okay we talk a lot about the smartest primate but what’s the dumbest? Like you just look at them and there’s no thoughts head empty sort of deal?
This is a challenge because like many things, intelligence is a social construct created by humans. Primate cognition studies tend to try to bridge human intelligence with that of other primates, but this is very challenging and we can't really judge other species by their ability to think like us. When it comes to primate intelligence we subscribe to the idea that every primate is exactly as intelligent as it needs to be to thrive in its ecological niche. Aye ayes look pretty clueless, but if you told us both to locate and extract a grub from a tree, even with tools I would absolutely be the one looking stupid.
That being said, there are many studies on primate cognition and how it can be measured. Heres one that proposes a quantitative measure for measuring intelligence by species. The breakdown of the results is here, for convenience.
