## 3 Results
### Research
#### 3.4.4. Research on Stakeholder's Perceptions of and Impacts on Sustainability and/or SD  
Several papers examined students, i.e., their perceptions, attitudes, competences, knowledge, and behavior regarding sustainability and SD, as represented in Table 7.  
Extending the focus to students, [PERSON] and [PERSON] [102] examined the relationship between the perceptions, attitudes, and environmental behavior of students enrolled in different specialization fields. Since the study was carried out at a single HEI, the authors proposed expanding the scope to other HEIs in future work, proposing to carry out more studies on EE and cross-cultural research. Taking a slightly different approach, [PERSON] and [PERSON] [103] examined how the diversity and significance of informal learning experiences support student learning with regard to sustainability. Specifically, the authors gathered the students' perspectives and experiences, asking how their HEI experience supported learning for sustainability. The analysis of the results revealed key themes: the communities of informal learning and the domains of informal learning. Further research on the interrelations between informal and formal learning was proposed to provide specific recommendations for practice and institutional commitments within HEIs. Our review \begin{table}
\begin{tabular}{c c c} \hline \hline
**Article** & **Research Theme(s)** & **Research Method(s)** \\ \hline [PERSON] and [PERSON] 2019 [102] & Research on environmental education (EE) & Survey \\ \hline [PERSON] and [PERSON] 2019 [103] & Informal learning & Case study \\ \hline [PERSON] 2016 [104] & Characteristics associated with & \\  & pro-environmental behavior & Survey \\ \hline [PERSON] et al., 2013 [105] & Sustainability attributes & Survey \\ \hline [PERSON] and [PERSON] 2017 [106] & Students’ perception of competencies and & \\  & values & Case study \\ \hline [PERSON] et al., 2019 [107] & Determining factors to develop critical & \\  & thinking focused on sustainability & Survey \\ \hline [PERSON] et al., 2019 [11] & Students’ knowledge of SDGs & Case study \\ \hline [PERSON], [PERSON] et al., 2013 [108] & Relationship between environmental & \\  & education (EE) and environmental & Survey \\  & knowledge, attitudes, and behavior & \\ \hline [PERSON] et al., 2018 [109] & Academic profile & Survey \\ \hline [PERSON] et al., 2018 [110] & Role of online training courses & Case study \\ \hline \hline \end{tabular}
\end{table} 
Table 7: Articles from the research category focusing on stakeholders’ perceptions of and impacts on sustainability and/or SD. indicates that a broader survey across HEIs would provide more information about the extent and relative importance of informal learning. [PERSON] [104] analyzed the students' characteristics with regard to their pro-environmental behavior and quantified the desirability of different environmental initiatives. The probability of pro-environmental behavior substantially increased with each additional year the student spent on campus, and informal learning was identified as an important driver of behavioral change. Initiatives related to energy conservation and recycling were seen as more desirable, although the preferences were highly heterogeneous. The authors planned to conduct future research to identify which student experiences on campus increase pro-environmental behavior, preferably in the form of a longitudinal study to more effectively control for unobservable characteristics. [PERSON] et al. [105] explored how students can be clustered based on their pro-environmental attitudes using statistical cluster analysis methods. Such clustering enables teachers to develop various teaching approaches and learning environments, depending on the different clusters identified. Our review results suggest that future research still needs to examine how these approaches and environments should be customized.