Have you ever blown through a red light in your car, and as soon as you got through the intersection you realized what you had just done? Other than worrying about whether a cop saw what you did, you may have realized that your eyes saw the red light, but your mind did not register the perception and respond as usual so you could stop and wait for the light to change. What this kind of incident illustrates is that human vision is made up of two distinct functions, what our eyes see and what our mind perceives. As well as a third factor memory, which allows us to not pay conscious attention to everything familiar our eyes see in the course of daily activities, otherwise we would never get anything accomplished if we had to consciously deal with everything in our vision familiar or not.