text: When using Facial Action Coding System their are many good reasons to use it for example paragraph 6 says "if you smile when a web ad appears on your screen, a similiar ad might follow. But if you frown, the next add will be different. also classroom computer could recognize when a student is becoming confused or bored, and could modify the lesson for the student. FACS works by whatching 44 major muscles in your face to see how they move to determine your expression.