It has been presumed that children who reverse letters or words see them backwards.  This is false.  They have directional confusion.  In the real world direction has no meaning.  For example, a chair is a chair no matter which way it is placed.  Changing direction does not change interpretation.  In the world of language direction changes meaning.  Connect the bottom of a chair and it looks like a "b".  Turn it 180 degrees it becomes a "d", flip it upside down and it becomes a "q" and flip it again it becomes a "p".  Thus, direction changes meaning.  The difference between "was" and "saw" is direction.