Harvard Reading Test

This was developed as an age test by an R&D department at  Harvard  
University Take your time and see if you can read each line  aloud
without a mistake. The average person over 50 years of age can't do  it! 

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 an cat
7.  This is old cat
8. This is fart cat
9. This is busy cat
10. This is  for cat 
11. This is forty cat
12. This is seconds cat

Now go back  and read the third word in each line from the top down, and
I betcha you  can't resist passing it on.