If you want to be more productive, hang out with productive people.

I would expect they'd only influence you about how they act at the time. If you hang out with someone who is usually productive, but at this moment is hanging out with a friend, it doesn't seem like it would help much.

Edit:

Also, this seems like a zero-sum game. You are less productive than people who are more productive than you, and they might not want that to rub off on them. Is there a good way to get around that?