Thatcher effect

is a phenomenon where it becomes more difficult to detect local feature changes in an upside-down face, despite identical changes being obvious in an upright face.

The Thatcher effect or Thatcher illusion is a phenomenon where it becomes more difficult to detect local feature changes in an upside-down face, despite identical changes being obvious in an upright face. It is named after the former British Prime Minister Margaret Thatcher, on whose photograph the effect was first and most famously demonstrated. (wikipedia)

thatcher effect, n.All

thatcher effect