focusing

I've been worried about the way my brain seems to dart hither and yon, never wanting to stay focused on any particular subject for long. I wondered if it was a form of Attention Deficit Disorder. Now I find I'm not alone - that the wandering mind seems to be a common occurrence. Some scientists have been studying the phenomona for several years trying to find out just why it happens and if there are ways to help us focus better. It seems two activities during which our mind wanders most are reading and driving (yeeow!) and that the mind wanders most when we try to prevent it from doing so. Here are a few articles about the subject:

Studies focus on why our minds drift
What happens when the mind wanders?
LIFE'S WORK; In the Age of Focus, How the Mind Wanders
Why the Mind Wanders

I wonder if we're seeing an evolution of the brain. These scientists say that the thing our mind most wanders to are mental "to do" lists. And that brings me back to thinking of ye olde caveman - what kind of "to do" lists was he thinking about?
1) find mammoth
2) kill mammoth
3) eat mammoth
3) butcher rest of mammoth
4) get back to cave with mammoth meat
5) draw pictures on cave wall

sorry, forgot what I was thinking about.