Enter the mind of a bored teenager to discover what happens in the brain when we daydream and find out what purpose it serves. -- 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, what exactly happens in the brain while you daydream? Elizabeth Cox takes a closer look at the science of daydreaming through the mind of a teenager.