So, the person asking the question says there are no independent studies. The only answer cites two studies about XGA displays and one study that claims that "some tasks can be performed faster". The title of the post on hn is: more is better, studies show. With all due respect but this is ridiculous.
Edit: So the question on stackoverflow was asked by you.
They compare screens up to 24 monitors and 42". The studies mentioned are clearly more reputable than the NEC and Apple sponsored ones you find on other sites.
I don't think that a study by a monitor vendor that shows that you need more and larger screens is really valuable.
Edit: So the question on stackoverflow was asked by you.