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摘要

Take a good look at the image above -what do you see? Close up It is clearly a faintly phantom-like image of Albert Einstein. Now step back 5 metres from the page and take another look. Notice anything different ? It's not just a crafty illusion. This sort of image is being used as a tool to understand better how our brains process visual scenes. On the practical side, some companies are interested in using them to conceal information from unintended observers -or to create printed advertising that morphs before your eyes.