29 Available online at www.koforiduapoly .edu.gh International Journal of Technology and Management Research 4 (2015) 29-46 Facial Expression Recognition – A Comprehensive Review 1 Ebenezer Owusu * , 2 Ebenezer Komla Gavua, 3 Yong-Zhao Zhan 1,2 Koforidua Polytehnic, Ghana, 3 Jiangsu University, China *kayowusueb@yahooo.com Abstract In this paper, we have provided a comprehensive review of modern facial expression recognition system. The history of the technology as well as the current status in terms of accomplishments and challenges has been emphasized. First, we highlighted some modern applications of the technology. The best methods of face detection, an essential component of automatic facial expression system, are also discussed. Facial Action Coding Systems- the cumulative database of research and development of micro expressions within the behavioral science are also enlightened. Then various facial expression databases and the types of recognitions are explained in detail. Finally, we provided the procedures of facial expression recognition from feature extraction to classifications, emphasizing on modern and best approaches. Then the challenges encountered when comparing results with others are highlighted and suggestions to alleviate the problems, provided. Keywords: FACS; Expression recognition; spatial; spatio-temporal; expression classification 1. Introduction The studies of facial expressions originally emerged as physiognomy, which is the general assessment of a person’s character or personality from his outer appearance, especially, from the face (Highfield et al., 2009). In a general sense the term refers to features of the face, when these features are used to infer the relatively enduring character or temperament of an individual. Most of these facial features have their basis in the bony structure of the skull, on which the soft tissues lie. These features include the shapes and positions of the major areas and landmarks of the face, such as the forehead, eyebrows, nose, cheeks, and mouth. In China and other Asian cultures, formal systems of face reading techniques developed in the first millennium B.C.E., and it was integrated with religious beliefs such as Confucianism (Highfield et al., 2009). Substantial confidence in such methods developed in these cultures, and physiognomic inferences included descriptions of character, suitability for certain positions, and predictions about life and death. In Western cultures, the association of facial features with a person's characteristic was first noted in the writings of the ancient Greeks in 4 BC. Much later, several pseudo-scientific and cultish movements exploited the inference of character from physiognomic features. As time expired, physiognomy studies slowly and imperceptibly vanished and replaced by facial expression recognition. The study of facial expressions had its root in the 17th century, when Le Brun officially gave a series of presentations on the subject in 1667. In his posthumously published treatise, “Méthode pour Manuscript apprendre à dessiner les passions” in 1698, he promoted the expression of the emotions in painting; which later had great influence on art theory for two centuries. Much of Le Brun’s idea is found in “The Perfect Imitation of Genuine Facial Expression” (Montagu, 1994). However, the modern day study of facial expression recognition started with Charles Darwin in the nineteenth century. Charles Darwin established the implications of facial expressions in humans and animals and introduced the deformation patterns to facial expression recognition (Darwin, 1998). “Among his many extraordinary contri butions Darwin gathered evidence that some emotions have a