You can't fool a dog.

[Catherine]

Playing the shell game with a dog is a lost cause. The dog is going to win every time. They can smell where the object is.

https://boingboing.net/2020/10/12/watch-...-game.html

I am guessing the treat is very good, otherwise the dog would not have had patience to keep playing the game. The dog wasn't even watching the movement of the cups. He knew he didn't need to watch. You can't fool a dog.