POSER: POsed vs Spontaneous Emotion Recognition using fractal encoding

Emotion recognition from facial expressions is a fundamental human ability that can be harnessed and transferred to machines. The ability to differentiate between spontaneous and posed emotions holds significant importance in various domains, including behavioral biometrics, forensics, and security. This paper introduces a novel method, called POsed vs Spontaneous Emotion Recognition (POSER), which leverages a modified version of the Partitioned Iterated Functions System (PIFS) to obtain a Fractal Encoding. This encoding is used for the first time as facial features to train a machine learning approach for the classification of emotions as either spontaneous or posed. Furthermore, by adapting the original architecture, we demonstrate the effectiveness of these features in distinguishing seven different emotions in controlled as well as wild environments, within a framework referred to as POSER-EMO. Experimental results are presented on the SPOS and DISFA+ datasets for the first classification problem, where POSER outperforms the state of the art, and on the CK+ and SFEW datasets for the second classification problem.