We don’t think about capital letters too much. We stick them on automatically at the start of sentences and proper names, and that’s about it. We see them on signs and newspaper headlines and generally think nothing of it. But there’s one place where they do call our attention: on the Internet.
ONLINE, IF WE SEE SOMETHING WRITTEN IN ALL CAPS, ESPECIALLY IF WE KNOW IT WAS WRITTEN BY A PERSON (NOT A MACHINE), we tend to think of it as shouting. On some level, this seems intuitive. It’s a visual metaphor: If shouting is talking with a big voice, then shouting in text would be writing with big letters. (Anyone figure out how to whisper?)
But is that the end of the story?
I investigated this question in my master’s thesis, and I found another important motivation for writing something in all caps: semantic highlighting. For example, if I write “I just wanted to say thanks for the PRESENT you got me,” it’s unlikely that I’m shouting the word “present.” Instead, I wanted to highlight that word’s meaning—and often in text boxes the only way to do so is by using capital letters.
Furthermore, I found that there is yet another use of all caps that has nothing to do with shouting: It’s to be colloquial. This usage is most often seen among the elderly, some of whom apparently enable caps lock so that they can see the letters more clearly—after all, they’re bigger.
But in Spain, for example, where I carried out my Master’s research, this behavior is much more deep-rooted: Written Spanish uses accent marks to distinguish certain sounds, but for a long time these accent marks were considered optional above capital letters. Therefore, people began to write in capital letters when they wanted to type faster and more casually, leaving off the accent marks. Hence all caps for colloquial writing.
This all goes to show that there can be multiple explanations for even the things we most take for granted—and that things, especially visual conventions, change across cultures.