Is UPPERCASE text more readable when used in button? [duplicate]

1. Should button text be all caps?
2. Is it easier to read all caps or lowercase?
3. Why is it harder to read all caps?
4. Do screen readers read all caps?

Should button text be all caps?

Should each word of the text in buttons be capitalized if it is a title (e.g. "Add Job Offer"), or should the button text be treated the same as a sentence when there are more than one word (e.g. "Add job offer")? This is open to interpretation and really depends on your brand guidelines or 'tone-of-voice'.

Is it easier to read all caps or lowercase?

It is thought by cognitive scientists and typographers alike, that lower-case text is more legible than upper-case. Yet lower-case letters are, on average, smaller in height and width than upper-case characters, which suggests an upper-case advantage.

Why is it harder to read all caps?

Readability is reduced with all caps because all words have a uniform rectangular shape, meaning readers can't identify words by their shape. Don't underline text. Reserve underlining for identifying links.

Do screen readers read all caps?

Screen readers may interpret capital letters as acronyms, and read them out letter-by-letter. Some developers brush this off as par for the course of using a screen reader. They say that it's a minor annoyance people who use screen readers are used to, just as we're used to our GPS mispronouncing street names.