Sometimes paying close attention can cause us to overlook the seemingly obvious. Then again, if we couldn't focus our minds on a single task, we'd never get anything done.

Consider, for example, that most radiologists fail miserably at the Gorilla Test when perusing a brain scan for signs of cancer. On one hand: Hey! Brain! You completely overlooked the gorilla! On the other: Good on you, Brain. Ignore the gorilla. You're supposed to be looking for cancer, remember?

In the latest installment of It's Okay to be Smart, Joe Hanson explores some of the science behind human attention, and how we use it to filter through the stimuli that surround us. As he explains, the brain's capacity for focus is something of a double edged sword – but then, maybe that's what makes humans so sharp.