Why Do We Need 120Hz/144Hz Monitors If The Human Eye Can't See Beyond 60Hz?

Human eyes cannot see things beyond 60Hz, so why are the 120Hz/144Hz monitors better? Human eyes cannot see things beyond 60Hz. So why are the 120Hz/144Hz monitors better? The brain, not the eye, does the seeing. The eye transmits information to the brain, but some characteristics of the signal are lost or altered in the process.