Mental Rotation - The Thatcher Illusion

Can you tell who this is? Well, that’s an easy one, isn’t it?

Our visual perception system is highly efficient at identifying faces. But it may come as a surprise to you that the picture you saw is actually:

While you would probably have no problem identifying the following as an upside down mouth, in the context of a full face view it’s hard to perceive that the mouth is flipped.

This phenomenon which is unique for faces, is called the “Margaret Thatcher Illusion” because it was first demonstrated using the former British prime minister’s face. It demonstrates that we process faces using different mechanisms when perceived in a normal fashion or upside-down fashion. When a face is presented in unfamiliar orientations, the activation of the representation of a face is triggered by the presence of elements, such as eyes, regardless of the element’s orientation, with regard to the rest of the elements. When the face is perceived in familiar orientations, in contrast, the correct relative orientation of the elements is necessary for recognition of the face as a normal face. Another thing that we can learn from this phenomenon is that, unlike other patterns that need to be mentally rotated for identification, the recognition of a face is independent of this mechanism.

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Written by Chen Rosner Or-Bach, (MA) Cognitive Psychology – Chen is a cognitive psychologist at Mind360, a leading scientific brain training games developer for boosting your memory, attention, executive functions, reasoning, and other key cognitive skills.