The 28 volunteers in the Princeton study were given 90 seconds to try to memorise a list of seven features for three different species of alien.
The idea was to re-create the kind of learning in a biology class. Aliens were chosen to be sure that none of the volunteers' prior knowledge interfered with the results.
One group was given the lists in 16-point Arial pure black font, which is generally regarded to be easy and clear to read.
The other had the same information presented in either 12-point Comic Sans MS 75% greyscale font or 12-point Bodoni MT 75% greyscale.
The volunteers were distracted for 15 minutes, and then tested on how much they could remember.
Researchers found that, on average, those given the harder-to-read fonts actually recalled 14% more.
They believe that presenting information in a way that is hard to digest means a person has to concentrate more, and this leads to "deeper processing" and then "better retrieval" afterwards.