I taught myself how to read when I was 3. Like most self-taught readers I learned pictographically – instead of breaking words down letter by letter, or phonically by sound, each word has its own shape and has its own meaning (think hieroglyphics or Chinese).
It turns out that many people read shape-wise, even those who learned to read in a more traditional manner. If it is a word our brain recognizes, it won’t bother to break it down into letters – it will just code it as its meaning and move on to the next word… unless your brain can’t translate the shape.
TOO MUCH CAPITALIZATION MAKES IT VERY HARD FOR THE BRAIN TO TRANSLATE QUICKLY!
When you use all capital letters the brain loses the ability to see the shape of the word and has to slow down and parse each letter separately.
Sometimes you want to do this – to break out a word or phrase and make sure people are paying attention. But you better make sure what you are capitalizing is worth the effort – because in this day of reading posts at a glance, anything that makes your message “difficult and slow” is likely to be passed over as not worth the effort.
Graphic designers and typographers have known about the “all caps trap” for decades. One of the ways they use them is for blocks of text that they don’t want people to read. Think legal notices and the “fine print” on pharmaceutical ads. The law says the information has to be there – it doesn’t say it has to be easy to read.
On social media, it’s also been generally agreed that all caps mean yelling. So now your message comes across as “loud, difficult, and slow”.
There is so much content out there, all struggling to gain attention. Don’t sabotage yourself by making your message hard to read. Because most people won’t bother.