Lewis is obsessed with transferring things from one container to another. It's a developmental need for mastery. If I give him a cup of water to drink and there's a cup on the table nearby he will pour the new water into the other cup before drinking. Here he transferring flour from one cup to another. I thought he might like to help me make pizza dough, but this is all he wanted to do. And when he got bored/adept with the cups he was using he up and opened the utensil drawer to get new things. He's good that way.