What we call "civilization" dates back no more than a few thousand years---and in many ways, our biology has not yet caught up to our culture. Back in our nomadic hunter-gatherer days, Mother Nature shaped us to respond to the natural environment in ways that kept us safe. Those who listened to their protective instincts lived to fight another day---and to have babies.

When a dry whirring at your feet meant Snake! and a glimpse of movement out of the corner of your eye might represent danger, instantly responding to sensory input could mean the difference between life and death. For most of us, distant phones and people passing in the halls have replaced such danger signals...but our bodies are still primed to pay instant attention to them.

These represent examples of involuntary attention---times when our minds instinctively yank us out of productive focus. Involuntary attention isn't all bad; it still aids our survival, and can prove restful if you're not trying to work. Suddenly seeing a cloud shaped like a UFO or listening to the argument between a blue jay and a squirrel can be interesting or amusing. In the long run, it may even give you productive ideas. 

But involuntary attention does you no good when you need to clear your to-do list. For that, you must engage your voluntary attention: the productive trance your ancestors learned to use when hunting, making stone tools, and carving farms out of the wilderness. These three tips will make it easier.