Perhaps this depends on the speed of your brain? You know, different people score differently on IQ tests. For example, some score 140 while others score 70. I read (in the book IQ and the Wealth of Nations by Richard Lynn and Tatu Vanhanen, I think) that what an IQ test basically does, is measuring the speed of your brain.

So I guess intelligent people will be able to understand everything on 2x while dumb ones may not.