Take the test to see how old your brain is. My brain is around 23. Or maybe 28 depending on how much wine I've had. On one of my tries, I purposedly failed every section just to see if how old a brain could be. 120!
You'll be presented with a group of numbers. Memorize the positions of the numbers. The numbers will disappear and empty circles will remain. Attempt to click the circles in numerical order. Try it, it only takes a few minutes.
UPDATED: I changed my instructions based on John's comment so don't get confused and think he's really old.