[In this excerpt from noted game researcher and developer Jane McGonigal's new book Reality is Broken, games are broken down into several different types of satisfying work, suggesting many ways to engage players.]

Games make us happy because they are hard work that we choose for ourselves, and it turns out that almost nothing makes us happier than good, hard work. We don't normally think of games as hard work. After all, we play games, and we've been taught to think of play as the very opposite of work. But nothing could be further from the truth. In fact, as Brian Sutton-Smith, a leading psychologist of play, once said, “The opposite of play isn't work. It's depression.”

When we're depressed, according to the clinical definition, we suffer from two things: a pessimistic sense of inadequacy and a despondent lack of activity. If we were to reverse these two traits, we'd get something like this: an optimistic sense of our own capabilities and an invigorating rush of activity.

There's no clinical psychological term that describes this positive condition. But it's a perfect description of the emotional state of gameplay. A game is an opportunity to focus our energy, with relentless optimism, at something we're good at (or getting better at) and enjoy. In other words, gameplay is the direct emotional opposite of depression.

When we're playing a good game -- when we're tackling unnecessary obstacles -- we are actively moving ourselves toward the positive end of the emotional spectrum. We are intensely engaged, and this puts us in precisely the right frame of mind and physical condition to generate all kinds of positive emotions and experiences.

All of the neurological and physiological systems that underlie happiness -- our attention systems, our reward center, our motivation systems, our emotion and memory centers -- are fully activated by gameplay.

This extreme emotional activation is the primary reason why today's most successful computer and video games are so addictive and mood-boosting. When we're in a concentrated state of optimistic engagement, it suddenly becomes biologically more possible for us to think positive thoughts, to make social connections, and to build personal strengths. We are actively conditioning our minds and bodies to be happier.

If only hard work in the real world had the same effect. In our real lives, hard work is too often something we do because we have to do it -- to make a living, to get ahead, to meet someone else's expectations, or simply because someone else gave us a job to do. We resent that kind of work. It stresses us out. It takes time away from our friends and family. It comes with too much criticism. We're afraid of failing. We often don't get to see the direct impact of our efforts, so we rarely feel satisfied.

Or, worse, our real-world work isn't hard enough. We're bored out of our minds. We feel completely underutilized. We feel unappreciated. We are wasting our lives.