What Is Visual Discrimination and Why Is It Important in PreK and Kindergarten?

My defining moment as an educator was in one of my first graduate courses. My professor gave us a decodable book she had created with symbols. As we started reading, we had to continue to look back to the first page to remember what letter of the alphabet was represented by which symbol. MY HEAD HURT and my stomach churned a little! This is what it must have been like for my then second graders who were trying to learn how to read! WOW !