An Approach for Selecting the Most Explanatory Features for Facial Expression Recognition

The objective of this work is to analyze which features are most important in the recognition of facial expressions. To achieve this, we built a facial expression recognition system that learns from a controlled capture data set. The system uses different representations and combines them from a learned model. We studied the most important features by applying different feature extraction methods for facial expression representation, transforming each obtained representation into a sparse representation (SR) domain, and trained combination models to classify signals, using the extended Cohn-Kanade (CK+), BU-3DFE, and JAFFE data sets for validation. We compared 14 combination methods for 247 possible combinations of eight different feature spaces and obtained the most explanatory features for each facial expression. The results indicate that the LPQ (83%), HOG (82%), and RAW (82%) features are those features most able to improve the classification of expressions and that some features apply specifically to one expression (e.g., RAW for neutral, LPQ for angry and happy, LBP for disgust, and HOG for surprise).