Now every time I reach for my pocket (or Dad reaches for his pocket), they think there is a treat.
Whenever my hand was partially closed, my boy would stick his nose into it, to see if I was holding a treat.

I kept one of his treats in a ziploc bag. When he was older, I used that as a hearing test. While he was looking the other way, I would quickly open the bag, and the "zip" sound, would make his head twirl around to see where the treat was.