(NYTIMES) - Humans have a natural talent for concentration. I recently watched a child crouching among pebbles at the beach. He spent eons sorting among sea-worn ovoids - not vapidly, but with an air of zealous exploration. Finally, he found what he sought: the perfect pebble. (What made it perfect? I don't know. Doesn't matter.)

The quest wasn't over. Having captured his specimen, the kid toddled over to the shallows and dropped his perfect pebble into the water. It splashed and sank. A vast stretch of time passed as he attempted to relocate the same pebble. When he did, the sense of accomplishment was visible and sublime. Nobody observing this young pebble connoisseur could doubt our innate ability for concentration. Which prompts the question: When was the last time you spent an hour in energetic focus? Or longer?