# Towards High Usability in Gamified Systems: A Systematic Review of Key Concepts and Approaches
## 3 Results
To better understand the importance of each of the usability classes, we traced back from the generalised recommendations to the pre-merger ones to have a look at how many individual recommendations of the given nature were mentioned in the selected papers (see Figure 5). Although the totals given at the bottom of the Table 5 already provide certain hints, the summary given in Figure 5 clearly shows that the majority of the identified recommendations were aimed at improving the I2-learnability of gamified systems (\(n=78\)), with I3-operability a distant second (\(n=40\)). Speaking of the classes based on [PERSON]'s heuristics, it must be noted that there were only 12 recommendations overall related to consistency and standards (N2) and 14 related to help and documentation (N10). The matters concerning user interface appearance or aesthetics seemed to be the least important to the researchers. Table 6 reveals a relationship between [PERSON] heuristics, ISO 25010 usability characteristics and all 20 of the selected publications that helps to better understand the importance of these aspects to the different authors. One usability characteristic and four heuristics have dependencies with all of the publications, namely: N1-visibility of system status; N2-match between system and the real world; N5-error prevention; N9-helping users recognize, diagnose, and recover from errors; I2-learnability. On the other hand, three heuristics and one usability characteristic could only be mapped to less than half of all of the selected publications. Those were heuristics N4-consistency and standards (\(n=6\)), N8-aesthetic and minimalist design (\(n=9\)), N10-help and documentation (\(n=7\)) and the usability characteristic I6-user interface aesthetics (\(n=9\)). Additionally, it is noteworthy that only three publications have outlined recommendations related to all of the usability heuristics and characteristics. After establishing the dependencies between publications and usability heuristics/characteristics, we wanted to understand the relationship between the way usability recommendations were positioned by the authors and the nature of these recommendations. Figure 6 shows how many of the selected papers mentioned at least one recommendation of the given nature and for a given gamification target audience or application domain. We can see, for example, that all six papers aimed at gamified systems for children, mentioned at least one usability recommendation concerning learnability, but only two of such papers mentioned the recommendation(-s) related to user interface aesthetics. This suggests that user aesthetics were considered less critical than learnability when developing gamified  
\begin{table}
\begin{tabular}{c c c c c c c c c c c c c c c c c} \hline \hline \multirow{2}{*}{**Papers**} & \multicolumn{10}{c}{**Nielsen’s Heuristics**} & \multicolumn{10}{c}{**ISO 25010 Usability Characteristics**} \\ \cline{2-13}  & **N1** & **N2** & **N3** & **N4** & **N5** & **N6** & **N7** & **N8** & **N9** & **N10** & **I1** & **I2** & **I3** & **I4** & **I5** & **I6** \\ \hline
[33] & \(  
systems for young audiences. Note that there are only seven intersection points on the diagram, where there were no recommendations of the given nature for the specific target audience or gamification application domain. To gain an even better understanding of these relationships, we again traced back from the generalised recommendations to the initial ones presented in the selected papers and repeated the calculations given in Figure 6. The result is presented in Figure 7. Here, we can see that the learnability recommendations were suggested considerably more often when talking about gamified systems for children (\(n=31\)) than when giving recommendations aimed at gamified systems for the elderly (\(n=13\)). Of course, one must not forget that there were six papers that talked about children-oriented gamified systems and four that discussed those for the elderly (Table 4).