“…Number of Papers Papers joy 3 [19,20,22] joy, neutral 2 [21,24] joy, sadness 2 [21,37] joy, fear, sadness 2 [26,34] joy, disgust, sadness, neutral 1 [25] joy, anger, sadness, neutral 2 [38,39] joy, anger, fear, sadness, neutral 2 [28,30] joy, anger, fear, disgust, sadness, surprise 1 [17] joy, anger, fear, sadness, surprise, neutral 2 [31,33] joy, anger, fear, disgust, sadness, neutral 1 [36] joy, anger, fear, disgust, sadness, surprise, netural 4 [27,29,32,35] In some papers, only two-class recognition was performed. In those papers, joy is recognized as a class combined with no-joy in three papers, with a neutral state in two papers, and with sadness in two papers.…”