Unless you’re a particularly earnest kind of grammar nerd, you probably don’t spend much time thinking about punctuation. Yet punctuation is what provides great literature with its excitement (!), decisiveness (.) and intrigue (?).

This is why people have been so intrigued by a new series of graphic visualizations by Adam Calhoun, who by day is a neuroscience research fellow at Princeton. In a series of graphics that were first posted on Medium, Calhoun extracted all of the words from some of his favorite books, leaving only the punctuation.

Adam Calhoun

It might not seem like much at first, but when you compare literary works side by side, the images start to reveal something fascinating about the author's style.

For example, the image below shows two of Calhoun's favorite books, which are written in very different styles. On the left is "Blood Meridian" by Cormac McCarthy -- an author whose style is direct, to the point and full of action. On the right is "Absalom, Absalom!" by William Faulkner, who, as you can tell, has a much more complex style, with lots of parentheticals.

Adam Calhoun. "Blood Meridian" by Cormac McCarthy is on the left, while "Absalom, Absalom!" by William Faulkner is on the right.

Calhoun also created some charts to show just how the use of punctuation differs. On the left below, you can see that "Blood Meridian" is written mostly in declarative statements, with just a few commas and question marks, and an extremely rare exclamation point. On the other hand, "Absalom, Absalom!" is like a treatise on how to use punctuation marks.

blood meridian absalom

Here is how some other books compare on the same measures. Among other things, the chart shows that "A Farewell to Arms" relies heavily on dialogue, and "Alice in Wonderland" uses a fair amount of exclamation points.

Adam Calhoun

Calhoun also graphed how these books compare in terms of sentence length. Once again, William Faulkner is an outlier, with lengthy sentences of more than 40 words each on average. "A Farewell to Arms," by Ernest Hemingway, looks terse by comparison.

Adam Calhoun

The graphic looks different, however, when you break it down by the number of words between clauses -- the words between each punctuation mark, whether it's a period or a comma. Because Faulkner uses so many commas and parenthesis, "Absalom, Absalom!" has relatively few words per punctuation mark. But "Blood Meridian," which uses few commas, has more.

Adam Calhoun

Finally, Calhoun followed a reader suggestion and created colorful heatmaps out of the full punctuation of each book. In the graphics below, periods, question marks and exclamation marks are red. Commas and quotation marks are green, and semicolons and colons are blue.

Adam Calhoun

The graphics show just how important punctuation is to a work of literature -- how, even though we pay little attention to periods, commas and exclamation marks, they determine the style and feeling of our favorite works of literature.

“Who doesn't love a perfectly crafted sentence? But who has a favorite comma or semicolon? Yet it is the fundamental structure to everything that we write,” says Calhoun.

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