Would you get more done if you drank a bit more water?

A few years ago, I was reading a funny and informative book by Mary Roach called Grunt: The Curious Science of Humans at War. It’s a book about the scientists who work behind the scenes to support the US military.

In one interview, the author was put on a treadmill so the research scientist could demonstrate his work. They monitored her exertion and subsequent rehydration. Later, they informed her that she is what they call a “reluctant drinker.”

Apparently, some of us have a natural instinct to avoid drinking much water. We just don’t feel very thirsty. As a result, we often fail to drink enough water to replenish states of mild dehydration.

I immediately knew I was in that group. My wife often asks if she can drink my nearly full cup of water at restaurants after she has finished her entire glass. As a child, I used to wonder why people took water bottles with them on long hikes.

But now, as a...