Is Mirrors Reversed on the Horizontal Plane Relative to Your Head?

Simon asks why mirrors only reverse the reflection on the horizontal plane relative to your head. There was a thought that it was due to your eyes being on a horizontal plane. But if you close one eye, the image is still reversed. And if you tilt your head sideways, its still reversed in this way. I mean, i don't know the answer, but i love to hear you guys discuss it. Thanks and keep up the good work.