I read the article I'm think of years ago, probably around 2003. I can't find it right now; all that comes up now is how money makes people less empathetic, which is not what I'm thinking of, though I have posted on it before.

Anyway, the thrust of the article was that "happy people" as defined by the study the magazine was writing about, are generally more content with their lives and so are generally less interested in the well-being of other people.

This article touches on a study that may have contributed to the one I'm thinking of:

Yet too much attention to detail can interfere with basic day-to-day functioning, as evidenced by research from Queen's University psychologist Kate Harkness, who found that people in a depressed mood were more likely to notice minute changes in facial expressions. Meanwhile, happy people tend to overlook such second-to-second alterations—a flash of annoyance, a sarcastic grin. You probably recognize this phenomenon from interactions you've had with your partner. While in a bad mood we tend to notice the tiniest shifts and often can't seem to disengage from a fight ("I saw you roll your eyes at me! Why did you do that!?!"), whereas when we're in a good mood, we tend to brush off tiny sleights ("You tease me, but I know you love being around me"). The happiest people have a natural emotional protection against getting sucked in by the intense gravitational pull of little details.