Take your time

This was developed as an age test by the R&D Department at Harvard University . Take your time and see if you can read each line out loud without a mistake. The average person can't do it!  This is really difficult, not so easy, so be careful. 

      1.     This is this cat 
      2.     This is is cat 
      3.     This is how cat 
      4.     This is to cat 
      5.     This is keep cat 
      6.     This is a cat 
      7.     This is fool cat 
      8.     This is busy cat 
      9.     This is for cat 
      10.   This is forty cat 
      11.   This is seconds cat 
 
Now go back and read the third word in each line from the top down