Ada deliberately places readability before writeability. It's interested in the maintainability of large mature programs, and isn't intended for rapid application development.

I don't have enough experience with Ada to comment on whether its verbose and keyword-heavy syntax succeeds in this goal.

Ancedotally, I agree with zerr's comment below. Its generally not the syntax/keywords that make code hard to read, or easy to maintain. If you're familiar with the language, you learned to parse those basically sub-consciously.

For me, its always the var/function names and comments that determine how readable a program is.

Code is not a prose. C-like syntax is much easier to read compared to Ada/Pascal's text blobs.

According to studies which we have none of right now.

So that's like... your opinion, man.

Besides, if the prose would have been preferable over symbols, we'd be writing e.g. "an unknown number of apples summed up with an unknown number of pears equals to one hundred entities" instead of "x + y = 100" in math classes :)

That's a caricature. We sometimes use words for summation, e.g. Python's sum and fsum functions. I do wonder though if people had to write like that before the development of modern mathematical syntax. Even the '=' symbol is relatively young. Wikipedia tells me it was invented in 1557.

SQL is another 'wordy' language. There are many, many things wrong with the SQL language, but I wouldn't say its wordiness is one of them.