Here's how smart they are.
I started trapping in a squirrel size cage. Opened on two ends and the bait was in the middle. After catching the first one, I watched all the others go in the door, reeeaaaacccch to the bait, leaving one foot outside to keep the trap door from catching when it fell. I moved up to the raccoon size trap.
On top of a metal pole, I had a "Squirrel-Proof" feeder. One of those that has a bar for birds, but the weight of a squirrel will close the feeder. My squirrels would climb the pole, reach around to fit the bar under their arm, which closed the feeder. With feet still on the pole, they pushed up, lifting the bar and opening the feeder.
I switched to hot pepper suet. Squirrels don't like it.