text: Facial expression does not have a set of rules you have to follow. For example, when someone is very angry, they might cry instead. In result, the computer might take it as sadness. Most of the time, facial expressions are easy to recognize. In paragraph 2 of "Making Mona Lisa Smile," it says, "Each expression is compared against a neutral face" (D'Alto 2). Everyone has different neutral faces. Most people have a good way of keeping in their emotions, making their face look blank.