http://www.craftideas4free.com/cognitiveillusio.html
Generally speaking, people perceive things around them by using two processes: bottom-up and top-down. Above is an optical illusion photo that I found by searching through Google images. It illustrates top-down visual processing, which means it is driven by the need to accomplish some goal. There are two different images here: one is a profile view of a young woman with her head turned away from the viewer and the other image is an older woman whose nose in the younger woman's jawline and mouth is the younger woman's necklace.This photo is a great example of top-down visual processing because it shows how our perception is bias - meaning we favor what we are looking for. To perceive the old lady, the mind must be focused on the task at hand. It is difficult to see the two images at the same time unless your perception has detected both separately.
