“…Rapid Feedback [4,20,[22][23][24]27] Freedom of Choice [9,20,24,25,27] Freedom to Fail [4,20,[22][23][24]27] Narrative [20][21][22][23][24] Competition [9,21,22,[25][26][27] Cooperation [21,22,25,27] Points [7,9,25,28] Badges [9,11] Leaderboards [9] Leveling Up Progress Bar and Unlocks [4,9,22,27] Game Level [4,23] External Rewards [9,22,26] For gauging the success of the intervention, the survey instrument was the most frequent evaluation metric used by authors, which was present in 8 out of the 15 papers (53%). While 5 out of these 8 papers had the survey as their only metric, the other 3 used this ins...…”