Safe to Stay: Psychological Safety Sustains Participation in Pull-based Open Source Projects

TL;DR

This study investigates whether psychological safety (PS) within open-source software projects can be observed and does so by deriving a PS proxy from pull request (PR) interactions. Using 60,684 PRs across 26 repositories, it builds a PS index (0–$10$) and tests its association with contributors’ short-term (12 months) and long-term (up to 2024) sustained participation via three logistic regression models. The results show higher PS predicts greater likelihood of sustained participation, with a strong early effect and a smaller but still significant long-term effect; however, prior participation emerges as a stronger predictor of future engagement when included. The work offers a scalable, data-driven method to quantify PS in OSS from PR data and highlights PS as a meaningful, but not sole, driver of contributor retention in open-source projects.

Abstract

Background: Psychological safety refers to the belief that team members can speak up or make mistakes without fear of negative consequences. While it is recognized as important in traditional software teams, its role in open-source software development remains understudied. Open-source contributors often collaborate without formal roles or structures, where interpersonal relationships can significantly influence participation. Code review, a central and collaborative activity in modern software development, offers a valuable context for observing such team interactions. Aims: This study investigates whether team-level psychological safety, inferred from code review activities, is associated with contributors' sustained participation in open-source projects. Method: Using data from 60,684 pull requests across multiple repositories, we developed a psychological safety index based on observable cues such as merge decisions, comment activity, interaction diversity, and mentions. We analyzed the relationship between this index and contributors' short-term (within 1 year) and long-term (over 4--5 years) sustained participation using three logistic regression models. Results: Contributors are more likely to remain active in repositories with higher levels of psychological safety. Psychological safety is positively associated with both short-term and long-term sustained participation. However, prior participation emerges as a stronger predictor of future engagement, reducing the effect of psychological safety when accounted for. Conclusions: This study introduces a scalable, data-driven approach to measuring psychological safety through pull request data and provides new empirical evidence of its relevance in sustaining participation within open-source development.