It's amazing what research will reveal to those who seek it out to improve themselves or the things they do. An article in Scientific American shared a study by researchers at the University of Michigan that showed that simple unadorned fonts influenced subjects to complete assigned tasks and improved the subjects attitude, making them more positive during the process.
What does this mean to you? If you do presentations, skip the fancy, hard to read fonts. They're pretty, but slow the brain down to the point that the subject's brain is tired from trying to read the directions that doing the directions seem harder. In short, the brain interprets the ease of reading the directions as an indicator of how easy the tasks will be to complete.
Solid research yields the same results time after time, so if one duplicates a study's process and factors, one can expect the same results. Get your participants engaged by adjusting your handouts and other materials.