It's funny, because some dogs "get it," and some dogs just don't. Gracie, our beloved (slightly retarded we think) 3/4 Great Dane 1/4 Lab my family got when I was in high school just did not understand fetch. She didn't even understand that she could catch FOOD thrown to her. We finally gave up, after being afraid somebody'd arrest us for dog abuse for throwing bits of hot dog to her and watching them bounce off her face! Once it hit the ground, if we pointed to it, she'd suddenly discover it and eat it. She never was interested in catching or chasing a ball, so fetch wasn't even remotely possible!

He's young, so being a retreiver just means he probably likes to carry stuff around in his mouth. The "bringing that something back to you" is definitely a learned behavior!