When we are awake, with our eyes open, we have the impression that we see the world vividly, completely, and in detail. But this impression is dead wrong. As scientists have devised increasingly elaborate tests to find out what is stored in the brain about the state of the visual world at any instant, the same answer has come back again and again—at any given instant, we apprehend only a tiny amount of the information in our surroundings, but it is usually just the right information to carry us through the task of the moment.
—Colin Ware - Visual Thinking for Design
The one-tenth of a second or so that it takes to make an eye movement is such a short time in terms of the brain’s neuron-based processing clock that it seems instantaneous. Our illusory impression that we are constantly aware of everything happens because our brains arrange for eye movements to occur and the particularly relevant information to be picked up just as we turn our attention to something we need. We do not have the whole visual world in conscious awareness. In truth, we have very little, but we can get anything we need through mechanisms that are rapid and unconscious. We are unaware that time has passed and cognitive effort has been expended.