I use an app called Lumosity to fill up some free time with brain exercises. It’s a fun way to keep that big muscle inside your head in shape with things like puzzles, memory games and speed match. I highly recommend it but that’s not my point right now. The neat thing about the Lumosity app is that it tracks your sleep cycle. Which got me thinking, is my sleep affecting my mental performance? The answer should be obvious but I wanted proof. So I started tracking and the answer is a resounding yes. When I get less than 8 hours of sleep my scores on everything from memory to reaction time are down by about 20%. In other words, I’m 20% dumber when I don’t get enough sleep. Think about that one next time you’re thinking about staying up late.