“…Automatic smile detection has been already addressed considering different issues and exploring various dimensions (see for example (Whitehill, Littlewort, Fasel, Bartlett, & Movellan, 2009)). The proposed solutions vary indeed whether one wants to detect the presence or the absence of smile (An, Yang, & Bhanu, 2015;Chen, Ou, Chi, & Fu, 2017;Guo, Polania, & Barner, 2018;Shan, 2012;Zhang, Huang, Wu, & Wang, 2015) or rather one wants to estimate smile intensity (Bartlett, Littlewort, Braathen, Sejnowski, & Movellan, 2003;Bartlett et al, 2006;Girard, Cohn, & De la Torre, 2015;Jiang, Coskun, Badokhon, Liu, & Huang, 2019;Shimada, Matsukawa, Noguchi, & Kurita, 2010;Vinola & Vimala Devi, 2019). The methods applied also change if one is interested in classifying single face image (An et al, 2015;Chen et al, 2017;Guo et al, 2018;Jiang et al, 2019;Shan, 2012;Shimada et al, 2010;Zhang et al, 2015) rather than proposing a dynamical annotation of a video recording (Freire-Obregón & Castrillón-Santana, 2015).…”