Recognize Efforts Regularly
Sure, there are a ton of studies done on this, but here is my very unscientific personal take. When team members can make decisions about how they work on projects, they are more engaged and connected to the project outcome. When they see how potentially dropping the ball would affect the entire team, they step up. When they feel like what they are doing is impactful and valued, they are naturally motivated to learn more, and be even better team members.