Laughter is a sign.
How is your team chemistry? How much fun do you have? One of the obvious measures of fun is simply laughter. When was the last time your team laughed together? Is it even allowed? Or is the team culture like a library? I am not talking about encouraging an ineffective goofiness where people do not take themselves or the team seriously. I am talking about a general playful banter that occurs between teammates who enjoy working together. A laugh is meant to be shared and great teams are not afraid to share them.