Ravens are smart. Smart enough that scientists have to be ingenious just to come up with experiments that show how smart they are. Let me try to describe what they did.
Ravens like to hide food for later use. They also try to keep other ravens from discovering where they've hidden it: they behave differently when another raven is present, hiding it more quickly and avoiding going back to a cache where they've already hidden food.
In this study, the birds had learned they could look through a peephole to see into the next room. The scientists then played the sound of another raven in that room (but there wasn't actually one there). If the peephole was open, the raven acted as if a competitor might be watching it, avoiding revealing where it had hidden food. But if the peephole was closed, it didn't.
Consider everything that involves. The raven understood how the peephole worked, understood that other birds could use it just as well as it could, understood that the bird it was hearing in the next room might be watching it when the peephole was open, but not when the peephole was closed, then behaved in a way to manipulate what that other bird would see.
I'd say that compares favorably with the intelligence of a lot of humans.