I first noticed this from my nephew, Alan Go. My late dad came from a family of 10 brothers and sisters so you can expect me to have cousins that are way older than me. And Alan Go was the son of my older cousins so me and Alan did not really have our ages too far apart. During out BMX years, when fixing bicycles, I noticed Alan when tightening a bolt, or exerting some physical effort, his lips go near to his gums and shows his teeth and the sides of his mouth stretch as if he was going to smile, be he is not smiling. And it is in perfect sync with his physical effort. The more physical effort needed, like when he opens a tight bottle, the more his lips go into that certain position.
I notice this early in other people, and I barely noticed myself, and when I started paying attention to myself, I have another mannerism, where when I exert some physical effort, my lips roll inward and in some occassions, my tongue partially goes out. I also noticed I do not only do this with physical effort, but with mental effort as well like when I am thinking hard on some computer program, or solving whatever PC problem I may have.
When I told this to my wife, she told me about her dad. That his lips keep moving in this certain manner, which I also observed and indeed, it does move when he is exerting some effort.
You think we’re all weird? Well Michael Jordan always takes out his tongue when going for a dunk. Sometimes even just for a lay-up, he takes out his tongue already. We are all weird. 😀