Question

To what extent does the ability to effectively read deptermine writing success?

Answer 1

According to me if u are a good reader, you get the sense of grammar and learn the rhythm of writing. By reading good literature you learn how to put thoughts in a proper sequence and how to create a sense of "reality" in your writing.

It is not necessary that a good reader will be a great writer too, but all good writers have been good readers in their time...

Answer 2

I think it actually depends. It might help or give you theoretical basis, but also i bet there are great writers that dont need it. Just like Mozart composing music at 6 years old without listening or studying other musical pieces.

For regular people, not gifted like Mozart, reading and improving the ability to read has always a possitive effect in writing.