I know what you mean Ebbie - but I'm not sure that example is too good, The Mudcatters in this bunch of Getaway Photos from 2004, taken at random, may look a rum lot at times, but they mostly look pretty engaged and frequently cheerful. As for this bunch, words fail me...

But I see a difference between people looking disengaged and withdrawn in a crowded place, for example, and looking frightened and tens. Here's a bunch of photos on flickr from the London Tube - mostly disengaged and withdrawn, it seems to me.

Actually, I think there's a lot to be said for consciously making a decision to look reasonably cheerful and at ease in public places like that. Even aside from it possibly lightening the mood for fellow passengers, our own internal moods can be modified by the way we use our face muscles. We generally think of it the other way rouind, but it works both ways.

Look miserable and you tend to feel miserable, look cheerful and you tend to feel more cheerful. Within limits, obviously.