To begin with, objectively, cats' brains are smaller than human brains — about 1/20 of our size — but they're also smaller on a relative basis. Their brains only make up .9 percent of their body mass, whereas a human brain takes up nearly 2 percent. This is one of those rare times where size doesn't matter. If you ever wonder why cats seem to delight in annoying you, it probably has something to do with their brains being 90 percent structurally similar to our own, according to Psychology Today. We're jerks, they're jerks; it's a good time. But their brain is similar to ours in ways that are known to improve function — primarily the surface area created by folds in the external brain matter and the complexity of their cerebral cortex.
The cerebral cortex is primarily used for cognitive processing. It's responsible for planning ability, language processing, and advanced reasoning skills. You wouldn't know it, since your cat cries to be fed when their food bowl has been half emptied, but those reasoning skills are somewhere in there. That's how they know to lay on your keyboard while your working or push your coffee cup off your desk. It's the reason why they don't listen. They're too smart to be your personal circus act.