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When we look at people, we look for patterns. We look to see how much someone’s left side looks like his or her right side. How much one side of a pattern or shape is like another side is called symmetry (SIMM-eh-tree). It’s Greek, and it means “measures the same”. Our brains use symmetry to help us recognize people. Try this:

What You Need

  1. handheld mirror
  2. class photograph of yourself

What You Do

  1. Test your face for symmetry by placing the mirror on its side, down the middle of your photograph. A line of symmetry exists where the mirror is placed if the reflection and the reflected portion of the object together look like the whole object.
  2. Try reflecting the left side of your face, then try reflecting the right side of your face.
  3. Is your face symmetrical? Do you recognize yourself?

What's Happening?

Most human faces aren’t quite symmetrical. Although we have two eyes and two ears, the left and right sides of every person’s face are just different enough to make every face one of a kind. We humans are so good at recognizing faces that half your face reflected in the mirror often hardly looks like you at all.

Bill Nye