There's a particular micro-expression I sometimes notice with people who are working on a software problem. I notice it when something goes wrong unexpectedly.
People who aren't particularly talented at SW development, for a brief instant, give a facial expression of disgust when something crashes or behaves incorrectly. People who are awesome at development, instead, have a look of amusement like they're actually looking forward to see what happened. These facial "micro-expressions" are really fast and subtle, you really have pay attention and it doesn't always work but I've seen it enough times to believe it shows something.
I think this goes back to the impulse to "improve" things that Norvig mentions. You really have to enjoy the act of programming, to be willing to improve on it. It's a kind of feedback loop. Just MHO.