## 3 Results
### Remaining Characteristics' Value Distributions

Table 4: _Cont._recorded the highest number of papers (2/12, 16.7%), while the years 2011, 2017, 2022, and 2023 recorded the lowest non-zero number of papers (1/12, 8.3%). As for regions and their number of papers, the United States has the highest number of relevant papers, followed by Taiwan, followed by several regions tied for third. Table 5 shows key data extracted from the 12 included papers. They relate to target subject, design approach, purpose, effectiveness, to mention but a few. For example, regarding target subject, the majority of the studies (5/12, 41.7%) were about language learning. Regarding design approach, all of the serious game designs were informed by the literature, with one-third of them being informed by user studies as well. Half of the games were evaluated by users; the other half were not. Three in four of the games were personal, while one in six was collaborative. Similarly, regarding effectiveness, three in four of the games were positive, while one in six was mixed. \begin{table}
\begin{tabular}{l l l l} \hline \hline
**Characteristic** & **Value** & **Papers** & **Count (\%)** \\ \hline \multirow{6}{*}{Target Subject} & Language learning & [36; 38; 39; 40; 43] & 5 (41.7\%) \\  & Mnemonic type comparison & [41; 46] & 2 (16.7\%) \\  & Chemistry & [44; 47] & 2 (16.7\%) \\  & Rehearsal and recall & [37] & 1 (8.33\%) \\  & Mathematics & [42] & 1 (8.3\%) \\  & Testing a new mnemonic & [45] & 1 (8.3\%) \\ \hline \multirow{2}{*}{Design Approach} & User-study driven & [37; 38; 42; 43] & 4 (33.3\%) \\  & Literature driven & [36; 37; 38; 39; 40; 41; 42; 43; 44; 45; 46; 47] & 12 (100\%) \\ \hline \multirow{2}{*}{User-Evaluated} & Yes & [36; 39; 40; 44; 46; 47] & 6 (50\%) \\  & No & [37; 38; 41; 42; 43; 45] & 6 (50\%) \\ \hline \multirow{2}{*}{Game Mode} & Personal & [36; 39; 40; 43; 44; 46; 47; 48; 49; 40; 43; 45; 46] & 9 (75\%) \\  & Collaborative & [41; 42] & 2 (16.7\%) \\  & Hybrid & [47] & 1 (8.3\%) \\ \hline \multirow{2}{*}{Age Group} & Adults & [36; 39; 40; 41; 46; 47] & 6 (50\%) \\  & Kids & [37; 38; 45] & 3 (25\%) \\  & Teenagers & [42; 43; 44] & 3 (25\%) \\ \hline \multirow{6}{*}{Level of Education} & Kindergarten & [37; 45] & 2 (16.7\%) \\  & Elementary School & [37; 38] & 2 (16.7\%) \\  & Middle School & [42; 43; 44] & 3 (25\%) \\  & High School & [43] & 1 (8.3\%) \\  & University & [36; 39; 40; 41; 46; 47] & 6 (50\%) \\ \hline \multirow{2}{*}{Game Outcome} & Positive & [36; 38; 40; 42; 44; 45; 46; 47] & 9 (75\%) \\  & Mixed & [41; 43] & 2 (16.7\%) \\  & Negative & [37] & 1 (8.3\%) \\ \hline \multirow{2}{*}{System} & Prototype & [36; 37; 38; 47] & 12 (100\%) \\  & Product & None & 0 (0\%) \\ \hline \multirow{2}{*}{Purpose} & Educative & [36; 38; 40; 42; 43; 44; 47] & 8 (66.7\%) \\  & Subjective & [37; 41; 45; 46] & 4 (33.3\%) \\ \hline \multirow{2}{*}{Type of Study} & Quantitative & [38; 41; 42; 43; 45] & 5 (41.7\%) \\  & Mixed & [36; 37; 39; 40; 44; 46; 47] & 7 (58.3\%) \\  & Qualitative & None & 0 (0\%) \\ \hline \multirow{3}{*}{Comparison} & Vs. control & [36; 42; 44; 46] & 4 (33.3\%) \\  & Vs. other experimental & [41] & 1 (8.3\%) \\  & Both & [37; 39; 43; 45] & 4 (33.3\%) \\  & No comparison & [38; 40; 47] & 3 (25\%) \\ \hline \multirow{2}{*}{Mnemonic Generation} & Manual & [36; 37; 38; 49; 40; 41; 42; 43; 44; 45; 46; 47] & 12 (100\%) \\  & Automatic & None & 0 (0\%) \\ \hline \multirow{2}{*}{Mnemonic Source} & Player & [36; 37; 41; 44] & 4 (33.3\%) \\  & Game/designer & [38; 40; 42; 43; 45; 46; 47] & 8 (66.7\%) \\ \hline \hline \end{tabular}
\end{table} 
Table 5: Synthesized characteristics.