Often what keeps us from recognizing what lies before us is a kind of afterimage, superimposed on our vision even after the stimulus is gone. Afterimages occur when photoreceptors are overstimulated because you look too long at an object without the small movements (saccades) that refresh the vision, leading to a decrease in the signal to the brain. Or they may occur because your eyes are compensating for bright light, and then you suddenly move into darkness. So too, if we wrap ourselves in the familiar without exposing our minds to fresh ideas, images are burned onto our brains, leaving
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