Face recognition 6 Facial Expressions 6 Facial expression recognition 6 Non-verbal human 6 Human emotion 4 K-nearest neighbors classifiers 4 Nearest neighbor search 4 Pattern recognition 4 Sets of features 4 Training example 4 Conditional random field 2 Dynamic approaches 2 Expression recognition 2 Gesture recognition 2 Random processes 2 State-of-the-art techniques 2 Static and dynamic approach 2