On a daily basis, you spend between a third and half of your waking hours daydreaming. That may sound like a huge waste of time, but scientists think it must have some purpose, or humans wouldn't have evolved to do so much of it. So, to figure out what's going on here, let's take a closer look at the mind wanderer-in-chief: the bored teenager. Wouldn't it be cool to discover something, anything, like even this plant? Just to be one of those explorers who sails around drawing stuff for years on end and everyone thinks they're a genius? But does anyone even do that anymore? Is there anything left to discover? And would I be tough enough to deal with dysentery or scurvy or piranhas or whatever? I barely have the endurance to make it through track practice. But I will. Any day now, I'll have the discipline to show up before sunrise and practice. I'll win all my races. Winning will become so easy I'll pick up other events just for fun. And once I'm in the Olympics, they'll have no choice but to crown me team captain, which I will graciously accept. And will I be nasty to the teammate who yelled at me? No. I'll just calmly say, "Hope you're in a better mood." Okay. Yours, and other people's daydreams might sound or feel something like that. Let's see what was going on. To see what parts of the brain are active when you're doing a task or thinking or daydreaming, scientists use brain imaging techniques that show increased blood flow and energy expenditure in those areas. These brain areas are active, working together, and communicating with each other. Taken together, they're called the executive network. When your mind starts to wander, a different set of brain areas becomes active. These areas make up the default mode network. The name "default mode" makes it sound like nothing is going on. In fact, for many years, scientists associated this pattern of activity with rest. But a closer look reveals that these are the brain areas involved when we revisit a memory, when we think about our plans and hopes, and yes, when our minds are wandering off on a wild daydream. The mind can wander to unproductive or distressing places and brood over negative past events, like an argument. It can also wander to neutral everyday matters, like planning out the rest of one's afternoon. But where mind-wandering really gets interesting is when it crosses into the realm of free-moving, associative thought that you aren't consciously directing. This kind of mind-wandering is associated with increases in both ideas and positive emotions, and the evidence suggests that daydreaming can help people envision ways to reach their goals and navigate relationships and social situations. Scientists think there may be two essential parts to this process. A generative phase of free-flowing ideas and spontaneous thoughts, courtesy of the default mode network, followed by a process of selecting, developing, and pursuing the best ideas from that generative burst, driven by logical thinking, thanks to the executive network. A host of imaging studies suggest that these two networks working in sync is a crucial condition for creative thinking. Taken together, the evidence clearly suggests the logical realm of the executive network.