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 40 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 person 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.