Harvard University test

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,
and I bet you can't resist passing it on.