When Margaret Thatcher became the first female Prime Minister of Great Britain, she turned the political world upside down. It is only fitting that an upside-down photograph of the Baroness would be used to demonstrate a fascinating way the brain processes the information it receives from the eye. This phenomenon would bear the name of the Iron Lady: “The Thatcher Effect.”

The human brain works around the clock to make sense of the information it receives. When visual cues come in from the eyes, the brain tries to process them using certain pre-programmed assumptions about the world.

In 1980, Peter Thompson, a professor of psychology at the University of York, took a photograph of Margaret Thatcher and made some subtle changes. He turned her mouth and eyes upside down. A viewer looking at the photograph with normal orientation would immediately spot the problem, but when the photograph is flipped upside down, the changed features miraculously blend into the photograph and appear completely normal.