People who suffer from math anxiety prefer easier-to-process dollar discounts (“$10 off the regular price of $50″) over percentage discounts (“20% off“) and sometimes make suboptimal decisions because of that preference, says a team led by Rajneesh Suri of Drexel University. The math-anxiety effect gets worse when consumers are more highly motivated to process information, such as when a reward is offered. Math anxiety is a condition in which people fear situations requiring the use of math skills and harbor worrisome thoughts about math.

Source: Math anxiety and its effects on consumers' preference for price promotion formats