I'm surprised the general response here is so negative. Besides the fact that it's obvious, research does in fact confirm that happier people smile more. And the average high school student is probably not focused on being cynical and grumpy whilst having his/her picture taken (though perhaps cultural norms around pictures have changed over the past decades).

Anyways, couple the happiness-smiling connection with a few other facts about human psychology, and this makes a lot of sense. (1) Emotional states in humans are contagious. We naturally tend to empathize with one and other, laugh together, and cry together. (2) We also naturally tend to mimic physical gestures made by people we are interacting with, often subconsciously. (3) Facial expressions actually influence our emotional state. Being happy makes us smile, but also smiling actually makes us happier.

It doesn't seem much of a leap from there that happiness would correlate inversely with divorce. In my take, this article is just reaffirming that naturally happy people are less likely to divorce.

Here's another interesting article about the contagiousness of happiness: http://www.npr.org/templates/story/story.php?storyId=9784878...