The thatcher effect was created by Peter Thompson. When we first see a face upside down we don't realize that the facial features such as eyes and mouth are right side up. Then when the picture gets flipped back to normal, it looks very messed up. We don't notice that the face is right side up because we are very tuned in to upright faces. Humans rely on how faces are made up to communicate and see emotions in others. So when the facial features are not upside down along with the head, we don't notice since our brains are used to seeing them a certain way. Now, if you look at the picture you can see that the upside down picture looks strange and not actually correct.
"Abraham Lincoln Optical Illusion." Weblog post. Mighty Optical Illusions RSS. N.p., 21 Apr. 2006. Web. 16 Mar. 2015.http://www.moillusions.com/abraham-lincoln-optical-illusion/ http://en.wikipedia.org/wiki/Thatcher_effect