The Thatcher Effect

Turn Obama right side up

Besides being upside down, the photo below looks normal right? Go ahead and turn it upright.

What you just experienced is called the Thatcher Effect, or Thatcher Illusion. It was first demonstrated in 1980 using a picture of former British PM, Margaret Thatcher. Hence, the Thatcher Effect. It demonstrates that human brains have trouble processing facial features when a face is inverted. Everyone experiences the illusion, even children.

The illusion suggests that humans process faces in a wholistic manner. Our brains make assumptions about what faces are supposed to look like and fills in the gaps. If our brains just ran a formula like eyes+nose+mouth+correct orientation = face, we would be able to tell something is jacked with Obama's picture. But in reality, our brains work more like I've seen this before+looks funny, but close enough = face.

The Thatcher Effect helps to explain why humans recognize faces they've seen before. We register faces as a configuration. We subconsciously make notes of the unique variations between faces and form a mental catalog. And because every human has a unique configuration we are able to accurately tell them apart. Our brains do this instantly and are so good at it that most of us can tell the difference between identical twins.