Aren't new facts grafted into our current understanding of the world based on how well they correspond with that understanding. And that understanding is not scientific from the start, in that we did not personally test everything we ever heard - we just assumed it.

Therefore, an 18 year old who was brought up an atheist being taught that science explains everything, can easily accept any new evidence/explanation (or at least entertain it) with regards to how evolution unfolded, while finding the idea of an intelligent designer completely ludicrous - especially when someone relates a story of that creator's miraculous working in their life.

On the other hand, an 18 year old who was brought up as a creationist can easily identify and believe a person who tells of a miraculous working, while finding it ludicrous that anyone can believe in evolution. The idea of God (and who that God is) seems so obvious that anyone who doesn't believe it is deemed to be willfully unbelieving.

So, how easily we accept new information (and interpretations thereof) is largely determined by how well it fits into our own worldview.

I would hypothesize that the number of new facts that are presented are not nearly as important as who and how they are presenting them. So perhaps we are misguided in trying to find that number, and should perhaps rather focus on how the facts are presented.