Another interesting article on Smashing Magazine, this one is titled “Size Matters: Balancing Line Length And Font Size In Responsive Web Design” that includes some research and lots of great links to other sources. Reading is such a weird process. It partially depends on how our goal because our approach can change whether we are reading casually, scanning with a purpose, or in an engaged manner and then is combined with how we really are always just looking for word shapes and not looking at individual letters in words. Interesting work in this field is shown that many people can still easily raed wrods taht hvae lettres in the wrong order as long as the length is the same and the first and last letters are correct.
There are a lot of factors that determine the readability of text, including screen resolution and the eyesight of the user. This article touches on quite a bit, so if you are interested in readability, go dig in.