WHEN YOU WRITE IN ALL CAPS IT SOUNDS LIKE YOU’RE SHOUTING.

Using capital letters to indicate strong feeling may be the most famous example of typographical tone of voice. But there are different kinds of strong feelings. Linguist Maria Heath asked a cross section of internet users to rate the difference in emotion between a message in all caps and the same message in standard capitalization. She found that all-cap styling made people judge happy messages as even happier: “IT’S MY BIRTHDAY!!!” feels happier than “It’s my birthday!!!” But it didn’t make sad messages any sadder: “i miss u” is just as pathetic as “I MISS U.” When it came to anger, the results were mixed: Sometimes caps increased the anger rating and sometimes they didn’t, a result which Heath attributed to the difference between “hot” anger (FIGHT ME) and “cold” anger (“fight me”).

A single capped word, on the other hand, is simply EMPHATIC. Looking at examples of all-capped words on Twitter, Heath found that the most common single ones included NOT, ALL, YOU, and SO, as well as advertising words like WIN and FREE: the same kinds of words that are often emphasized in spoken conversations (or commercials). When we want to emphasize something in speech, we often pronounce it louder, faster, or higher in pitch—or all three at once. All caps is a typographic way of conveying the same set of cues.

Gretchen McCulloch is WIRED's resident linguist. She's the cocreator of Lingthusiasm, a podcast that's enthusiastic about linguistics, and the author of Because Internet: Understanding the New Rules of Language, from which this piece is adapted.

Emphatic caps feel like the quintessential example of internet tone of voice, and sure enough, they’ve been around since the very early days online. Linguist Ben Zimmer found people in old Usenet groups explaining that all-caps meant yelling as far back as 1984. What’s more intriguing is that capitals were available for emphasis long before the internet as well. The linguist John McWhorter dates shouty caps back to pianist and writer Philippa Schuyler in the 1940s, while author L. M. Montgomery has a character use both capitals and italics for emphasis in her fictional diary entries of the 1920s, which another character criticizes as “Early Victorian”— meaning old-fashionedly melodramatic, even back then. Going yet further back, a newspaper in 1856 described a line of dialog with the phrase “This time he shouted it out in capital letters.”

Back in the heyday of personal letter writing, all-caps was just one part of a broader emotional ecosystem for expressing strong feeling, along with italics, underlining, larger letters, red ink, and other decorative formatting options. The emotional use wasn’t even the most prominent option: All-caps was widely used to avoid the idiosyncrasy of joined handwriting, such as in comic strips, on forms (“Please fill out your name in block capitals”), or in official documents by lawyers, architects, and engineers. Typewriters and early computer terminals made illegible handwriting less of a problem, but they also introduced a new one: They wouldn’t let you type italics and underlines or change font sizes (for that matter, many social media sites still don’t). This created a vacuum into which the preexisting but relatively uncommon shouty caps expanded.

This brings us to a puzzle. Early internet guides like the Jargon File, Wired Style, and website FAQs mentioned all-cap styling, but not to facilitate shouting, the way that *bolding asterisks* or _italicizing underscores_ were recommended to compensate for the lack of other formatting that can indicate emphasis, or a smiley face was recommended to facilitate sarcasm and joking around. No, they were generally trying to discourage it, meaning that a fair percentage of '80s and '90s computer users were writing their routine correspondence in all-caps. (The '90s version of “Oh my god, my boss doesn’t realize that periods are passive-aggressive” was “Oh my god, my boss doesn’t realize that all caps is shouting.”) Where did the idea that it was ever OK to type a full message in block capitals come from? After all, people have been handwriting in lowercase for over a thousand years, and even the melodramatic early Victorians didn’t capitalize everything. Why would anyone suddenly switch to all-caps on a computer?