“…They could benefit from 63 having knowledge of the user's emotion, especially with regards to 64 delivering more user-centric actions. Facial expression recognition 65 is a key point in the wave of research within HCI that aims to trans-66 late the user's emotional experience into a meaningful feedback, in 67 various areas, such as from a patient (e.g., suffering, annoyed, 68 depressed or comfortable) (Khosla et al, 2012;Lau, 2010), a student 69 (e.g., interested, puzzled or boring) (Bahreini,Nadolski,& Westera,70 2014; Ben Ammar, Neji, Alimi, & Gouardères, 2010;Whitehill, 71 Bartlett, & Movellan, 2008), or a customer (e.g., satisfied) 72 (Puccinelli, Motyka, & Grewal, 2010). 73 In a pioneer work, the psychologist Ekman and his colleagues 74 conducted extensive studies on how people from different races 75 express their emotions through facial expressions (Ekman, 1971; 76 Ekman & Friesen, 1976, 1977.…”