Doom is a palindrome for mood, the former perhaps describing the latter, at least in terms of books. An unusual study, published in the journal PLOS ONE, reports that words about emotions have almost universally decreased in frequency in English-language books over the last century.

The one exception: fear.

Researchers at the University of Sheffield did an analysis of five million 20th-century digitized books (provided by Google), looking for emotionally evocative words associated with six basic categories: anger, disgust, fear, joy, sadness and surprise.

"We were initially surprised to see how well periods of positive and negative moods correlated with historical events," said co-author Vasileios Lampos. "The Second World War, for example, is marked by a distinct increase of words related to sadness and a correspondent decrease of words related to joy."

There were broader findings, as well.

One, the emotional content of published English has been steadily decreasing overall for more than a century, with the exception of words associated with fear. And two, American English and British English have notably diverged. In particular, American English has become decidedly more "emotional" than British English in the last half-century.

Do these findings say anything about our actual well-being? Not necessarily.

"A remaining question is whether word usage represents real behavior in a population, or possibly an absence of that behavior which is increasingly played out via literary fiction," the authors write. "Books may not reflect the real population any more than catwalk models reflect the average body."

BODY OF KNOWLEDGE

A normal breath takes five seconds: two to inhale, three to exhale.

LIFE IN BIG MACS

One hour of light baking burns 170 calories (based on a 150-pound person) or the equivalent of 0.2 Big Macs.

GET ME THAT. STAT!

New rules implemented more than a year ago that require young doctors to work fewer hours without a break were supposed to reduce the chances of them making mistakes. However, a new University of Michigan study suggests just the opposite has happened.

The new rules mandate resident doctors work no more than 16 hours at a stretch (compared to the previous 24-plus), but the error rate (mistakes that affect patient care) among these doctors jumped from 19.9 percent to 23.3 percent.

One possible explanation: The doctors feel compelled to squeeze the same amount of work into a shorter work period.

STORIES FOR THE WAITING ROOM

According to the United Nations, more people in the world have mobile phones (6 billion out of roughly 7 billion) than have access to a functioning toilet (4.5 billion).

That's a bad call. Open defecation is linked to a host of ailments and diseases, such as diarrheal conditions that kill an estimated 4,500 children each day. There are economic harms as well. The U.N. says a lack of proper sanitation costs India more than $53 billion year in lost productivity, health costs and more.