Clear, legible fonts are supposed to be best for presenting information.
I was reading about the "Cognitive Reflection Test", a short set of "brain teaser" questions that have intuitively appealing wrong answers. It turns out that presenting such problems in a "disfluent", degraded font actually results in significantly more correct answers! The effort in reading the text apparently encourages systematic and analytic, rather than quick heuristic, processing.
Try it for yourself:
A bat and a ball together cost $1.10. The bat cost $1.00 more than the ball. How much did the ball cost?
If it takes five machines five minutes to make five widgets, how many minutes does it take 100 machines to make 100 widgets?
In a lake there is a patch of lily pads. Every day the patch doubles in size. If it takes 48 days for the patch to cover the entire lake, how many days would it take for the patch to cover half the lake?
(I deliberately tried to make the questions show up in a small, italicized font, in a very light gray on white, similar to the conditions in the study. Another group got normal-sized black-on-white text in the same typeface.)
Try to read the questions as is, without cheating by, say, selecting the text. Of course, the actual test subjects weren't given the background information I wrote!
The Cognitive Reflection Test: "Cognitive Reflection and Decision Making", Shane Frederick, Journal of Economic Perspectives 19(4), Fall 2005, pp. 25-42.
"Overcoming Intuition: Metacognitive Difficulty Activates Analytic Reasoning", Adam L. Alter, Daniel M. Oppenheimer et al., Journal of Experimental Psychology: General 136(4), 2007, pp. 569-576
Thank you Grinning Cat - interesting