There are six main types of stories in fiction. That’s what computer scientists found after teaching a machine to map the emotional arc of a huge corpus of literature. The overall research they did is fascinating (I wrote about it in greater detail here), but several smaller components of the work are compelling in their own right.

To prepare a machine to carry out a sentiment analysis, for instance, computer scientists had to assign a happiness index to 10,222 individual words. That way, as the machine scanned passages from books, it could assess the emotional arc of the narrative.

But how do you decide how happy a word is?

In this case, researchers at the University of Vermont and the University of Adelaide enlisted the help of the crowd. Using the website Mechanical Turk, where anyone can sign up for odd jobs—many of them related to academic research—researchers asked people to rate the happiness quotient of the words they encountered.

In the end, they had a huge list of words as ranked by happiness.

The happiest word: Laughter.

The least happy: Terrorist.

In the middle of the pack you’ll find words like particularly, list, brown, expectations, equation, index, and explain.

And though the results aren’t altogether surprising, it’s intriguing to see words grouped by happiness this way. Let’s start with least happy, so we can end on a high note.