The Thatcher Illusion
Thatcher illusion, named after Margaret Thatcher because her face was the
first to be used, illustrates the importance of viewing faces upright.
Faces are processed holistically, taking the configuration to be
the most important information. When faces are viewed upside-down, our
ability to process the configuration is disrupted.
One of the inverted faces below
has had the eyes and mouth re-inverted. It looks odd, but not too alarming.
By scrolling down to the bottom of the page, however, you can see how different
the face looks when it is upright.
Looks very different doesn't it!? In the inverted version,
you were only able to process the individual features, but when the faces
are upright, you are also able to gain configural cues. Those cues, in
the case of the face on the left, are decidedly wrong, although
the features are perfectly alright.
The Thatcher illusion was first published by Thomson (will include reference soon).