60Hz vs 75Hz

[WerzalNZ]

My monitor is stock 60Hz. But i have used EVGA pixelclock to overclock it to 75Hz and it is way smoother. But my friends just cannot see the difference between 75 and 60.

Can somebody please explain to me why they cant tell the difference? but i can

 

[Chicano]

Your eyes are more sensitive to the refresh rate... check the related and self explanatory comments here:

Monitor giving you a headache? Check the refresh rate.
http://blogs.msdn.com/b/oldnewthing/archive/2004/06/25/165762.aspx