Get Smarter in 20 Days N-back exercises improve 'fluid intelligence': Study By Sarah Whitmire, Newser Staff Posted Jun 4, 2011 1:58 PM CDT 7 comments Comments 'N-back exercises' might get this in shape. (Shutterstock) (Newser) – Some of this week's news was enough to turn your brain to mush, but a university psychologist has a way to get it back in under three weeks. His technique involves something called "n-back exercises," a type of mental training that tests your short-term memory of symbols or noises. Doing them 20 minutes a day for 20 days improves "fluid intelligence"—the ability to reason and solve problems—for up to three months, says his University of Michigan study. (Here’s an app we found free for Android, or this one is a desktop app.) More on the medical specifics here.