Table 2.

Categories and codes used in the analyses of the transcribed interviews.

Category	Code	Description
1. Intradisciplinarity (ID) vs. transdisciplinarity (TD)	Descriptions of TD	Descriptions of what transdisciplinarity means, in both general and concrete terms (citing examples), for example, by contrasting with multi- or interdisciplinarity
	Complexity	Characterizing TD in terms of complexity
	Intradisciplinarity (ID)	Describing and reflecting on intradisciplinary research in contrast to TD; limitations of ID are also addressed
	Difficulties and obstacles	Describing difficulties and obstacles in conducting transdisciplinary research with a focus on structural aspects
	Differing perspectives	Reflections on and comparisons between the different research perspectives and practices of the different fields
	Towards TD	This code describes intermediate steps from ID to TD, for example, through the interaction of two adjacent but different fields
2. Experiences of the joint research project	Research questions	Description of the research questions of the joint research project
	Humans as study objects	Descriptions of having human beings, here the tenants, be part of the study object and of interacting with them as part of the project
	Methods	Regarding the methods applied in the project, ID as well as TD
	Positive appraisals	Positive appraisals of successful elements or people in the project
	Mistakes and lessons learned	Descriptions of mistakes made in the project and what can be learned from them
	Not yet TD	Perception that work and effort are still needed for the project to be considered TD
3. Individual aspects	Previous experiences of TD	Descriptions of previous experiences of TD
	Attitudes towards and capabilities for TD	This concerns individual attitudes and capabilities argued to be necessary to successfully engage in TD research
	Learning for the individual	Descriptions of what has been learned in terms of new competences or knowledge from experiences of the project; how to learn about and get acquainted with the fields of the other participants
	Personal development	Descriptions of how the respondent has grown and developed as a person in terms of attitudes and abilities and not only in terms of competences as a researcher
4. Social aspects	Collective leadership	Descriptions of what collective leadership is and how it was manifested in the project; contrasting collective leadership to individual and formal leadership
	Cooperation	General descriptions of the nature of the cooperation within the project and the group
	Group dynamics	Descriptions of how the group changed and developed over time, and of measures to uphold a shared identity
	Competition	Description of how group members see each other and other research groups as colleagues rather than competitors
	Safe atmosphere	Descriptions of the importance of ensuring a safe and respectful atmosphere concerning each other’s expertise, and of measures to create such an atmosphere
	Shared language	Reflections on the importance of finding and using a shared language for key terms, data formats, article formats, etc.
	Introducing research to others	How to simplify, introduce, and teach research from one’s own field to participants from other fields