I claim no expertise in this subject, but maybe a lot of experience and observation. Let’s get that out of the way first.
First, let me say I am not a particularly good sight reader. I have gotten better through osmosis, maybe because I sit next to people who are, so it elevates me to some degree. It seems to me that some of the great sight readers might have a strong aptitude for math. See the opening remark: it is my observation and experience over the years, not fact or scientific study. They have the numbers and fractions right there in their heads, constantly ticking off like a computer. Easy stuff for them.
My problem with sight reading, I think, stemmed from my relying too much on my ear. I’d hear it the first time through and know how it went, rhythmically and the tune was in the vault already, so, once again I escaped really having to figure it out on my own.
So am I way off base or is there some validity to this?