The idea is to test our short term memory.

The best way to understand the test is to watch the chimps do it.

But here is a short explanation:

• For a very short time you are shown the digits 1 to 9, randomly positioned on the screen.
  
• Then they are all covered with white squares.
  
• Your task is now to click on the squares in numerical order, remembering where the digits are.

 Check Yourself