# Towards Adaptive Gamification: A Method Using Dynamic Player Profile and a Case Study
## 2 Previous Work
### Player Modeling  
User-centered techniques have been proposed to correlate game elements and different user profiles [8; 9]. Some of these techniques have focused on specific user characteristics such as motivation [10], personality traits [11; 12], learning styles [13], player types [4], and types of interaction with different activities [14]. Others combined different characteristics, such as [15] which took into account learning styles and player types to determine the types of educational activities and game elements to include in a learning pathway. In contrast, ref. [16] suggested using the context, interactions, gender and player type to decide, through rules, the next game element to display. Other works instead focused on emotions to predict the individual's performance in gamified tasks, which is information that could potentially be used to adapt the game features [17]. Specifically, in current adaptive gamification approaches, the most commonly used taxonomies of player types are Bartle [18], BrainHex [19] and HEXAD [20]. These taxonomies allow us to easily identify player types from questionnaires as well as establish the correspondence between these player types and the game elements [9]. A recent study [21] proposed the so-called MoMo (motivational value model), a new prediction model that combines the four categorization models--Hexad, Bartle, Big Five and BrainHex. MoMo was validated along with Bartle and BrainHex using health applications. Results showed that it could predict players' preferences better than the individual models. Questionnaires allow for the characterization of the player type of a user with a set of ratings. They determine the player type prior to the experience. For example, the HEXAD model distinguishes between six player types (achiever, player, philanthropist, disruptor, socializer and free spirit), and as result of the questionnaire, the user can obtain the following ratings: achiever 25%, player 18%, philanthropist 21%, disruptor 8%, socializer 10% and free spirit 5%. The decision of the final player type--and thus the most appropriate game element--usually relies on the predominant rating [4] or a combination of them [22]. As an alternative to questionnaires, a recent study [23] proposed to predict HEXAD player types through gameful applications. The authors created two applications. An interactive one resembling a questionnaire but with appealing look and gameful feedback, and another application in which users interacted with gamification elements by shooting snowballs. The former correctly predicted player types but the latter did not show sufficient variance to reliably predict HEXAD player types. However, users interacted with gamification elements that fitted their player type, which seemed promising and worthy of further study. In this work, we relied on the HEXAD player model and used the questionnaire as proposed and validated by [24]. However, it should be noted that in all the studies analyzed, the no-player type of player was not taken into consideration, a fact that suggests that, in some cases, the use of gamification is more detrimental than beneficial [25]. Thus, we also added the no-player player type to the HEXAD taxonomy, and we also considered for each user the assessment of all their ratings included in their player type. Certainly, as supported by different studies [26], the interpretation of the results of these questionnaires may not be very reliable. Even if the questionnaire is valid, the answers may be somewhat random or the results at the beginning may not persist during the experience depending on the moment or the mood of the user. In fact, in addition to questionnaires, some proposals in the literature also gathered user feedback on learning activities [14], or scores on different game elements during the experience. Thus, inspired by these works, we enriched the user model obtained from the initial questionnaire by means of user interactions and opinions during the course of the activity.