# Towards High Usability in Gamified Systems: A Systematic Review of Key Concepts and Approaches
## 3 Results
Only a minority of the analysed recommendations' lists were positioned by the authors as applicable independent of the nature of gamified activity (see Table 4). It was presumed that not defining the target audience and/or target gamification domain implied that these factors were deemed as having no influence on the importance of the defined usability recommendations. It is important to emphasise that not all of the authors positioned their recommendations as aimed at improving the usability or user experience of gamified systems, even if most of the given recommendations could, in fact, be interpreted as usability recommendations. Instead, these authors claimed that their recommendations' lists were intended for serious games developers and/or those striving to improve gamification mechanisms, user motivation, user engagement, adherence to the human/user centred design principles, or a combination of the above. The relationships between all of the three mentioned aspects of how the analysed lists were positioned are given in Figure 4. \begin{table}
\begin{tabular}{l c c} \hline \hline
**Target Audience** & **Percentage** & **Publications** \\ \hline Children & 6 (30\%) & [14; 16; 20; 23; 24; 25] \\ Adults & 2 (10\%) & [27; 29] \\ Elderly & 4 (20\%) & [17; 28; 30; 31] \\ Undefined & 8 (40\%) & [15; 18; 19; 21; 22; 26; 32; 33] \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Distribution of papers based on gamification target audience. Figure 4: Number of publications in relation to declared gamification target audience, gamification application domain and positioning of recommendations. To gain a better understanding of the nature of the recommendations proposed in the selected papers, the generalised recommendations R1-R30 were further analysed one by one and assigned to one or more general classes, based on their nature. Two classifications were used to group recommendations, namely:  
* [PERSON]'s heuristics for user interface design [9]. Heuristics serve as the most general usability principles available. Each recommendation had to be assigned to one or more of the following heuristics: N1. Visibility of system status; N2. Match between system and the real world; N3. User control and freedom; N4. Consistency and standards; N5. Error prevention; N6. Recognition rather than recall; N7. Flexibility and efficiency of use; N8. Aesthetic and minimalist design; N9. Help users recognize, diagnose, and recover from errors; N10. Help and documentation. * Usability characteristics defined in ISO 25010 [8]. Usability is a complex concept and its characteristics provide a more granular view. Again, each recommendation had to address one or more of the following characteristics: I1. Appropriateness recognizability; I2. Learnability; I3. Operability; I4. User error protection; I5. Accessibility; I6. User interface aesthetics. The mapping to [PERSON]'s heuristics was completed, based on the descriptions of the said heuristics given in [9] and its accompanying articles. Similarly, the mapping to the ISO 25010 usability characteristics was completed, based on the descriptions of these characteristics given in the standard and in the textbook literature on usability. Due to the lack of purely formal definitions, such mapping is deemed to be at least somewhat subjective, but this risk was mitigated by the fact that two of the authors of this paper have extensive experience in both the teaching of [PERSON]'s heuristics and usability characteristics and in using them as classifiers for software usability problems. Table 5 shows the mappings between the generalised recommendations collected from the papers and [PERSON]'s heuristics, as well as the ISO 25010 usability characteristics. Note that the recommendations R9, R19, R21, R22, R23, R26, R27 and R29 were dismissed from further analysis as they concerned the methodological or social aspects of gamification and were not related to the usability of gamified software systems.