Supplementary material [Appendix 1] for: Measuring psychological ownership and identity in a Finnish blood donor context

Having a donor self-identity is crucial for sustained blood donation. When new donors give blood, they develop a role-identity ("I am a blood donor"). As they continue to donate, this role-identity is validated, becoming part of their self-identity ("Being a blood donor is an important part of who I am"). Despite the link between donor self-identity and retention, there are no interventions that foster this identity without relying on repeat donations. Interventions enhancing psychological ownership over donations could impact donor retention. Psychological ownership ("this is mine") is the sense of ownership over both material (e.g., blood collection agency) and abstract (e.g., blood donation behavior) possessions. This ownership is linked to sustained volunteering behavior and is associated with identity. In an Australia study, psychological ownership towards a blood collection agency increased with past donation experience and was positively associated with donor self-identity. Interviews showed that Australian donors primarily express ownership over the donation process, not the agency. This study aims to replicate these findings in Finland by collecting similar questionnaire data from Finnish Red Cross Blood Service donors and modeling it with a structural equation model. The study includes pre-registered R analysis code for direct repetition.