*1.2.1 Judgmental coding scheme*

As the name suggests, the model classifies the expressions on subjective judgment. Prototypic expressions are a subjective measure of the texture like wrinkles, bulges, furs on the face, which is useful for judging the expression. Ekman and Friesen categorized expressions into six classes: Happiness (HA), Sadness (SA), Surprise (SU), Anger (AN), Fear (FE), and Disgust (DI) [5], which are portrayed in **Figure 1**. These six expressions serve as a ground truth label, and instead of distinguishing the comprehensive facial features, most FER systems attempt to recognize a small set of these prototypic expressions.

The other way of describing expression is using geometry of the face. Judgmental coding scheme based algorithms use appearance features for expression recognition. Descriptive coding scheme described in next section uses geometry of the face for expression recognition, which is more robust compared to judgmental coding scheme. However, extraction of exact Action Unit (AU) is challenging.
