Scaffolding is one of the critical features in a problem-based learning environment to address challenges associated with problem solving. While transfer of responsibility is considered as an ultimate goal in scaffolding that is adaptive and contingent, it is rarely studied and practiced. Thus, the purpose of this study was to inform a deeper understanding of one middle school teacher’s manner of soft scaffolding, which refers to just-in-time and contingent support, through teacher-student interaction to examine how transfer of responsibility was achieved. We investigated one middle school teacher’s forms of scaffolding during a problem of food systems and supply chains related multiple aspects of sustainability and social justice issues. Using conversation analysis, three discursive patterns in scaffolding emerged: (1) shifting patterns of turn-taking organization; (2) leaving room for the students to take responsibility by giving extended wait time; and (3) extending the discussion with different examples. The paper concludes with implications for PBL teachers and researchers.

脚手架是在基于问题的学习环境中解决与解决问题相关的挑战的关键功能之一。尽管责任的转移被认为是适应性和偶然性的脚手架的最终目标，但很少研究和实践。因此，本研究的目的是通过师生互动来研究如何实现责任转移，从而加深对一位中学老师的软脚手架方式的了解，这是指及时的和临时的支持。在食品系统和供应链问题中，我们调查了一位中学教师脚手架的形式，这些问题与可持续性和社会正义问题的多个方面相关。使用对话分析，出现了三种脚手架上的话语模式：（一）轮换组织方式的转变；（2）通过延长等待时间留出空间让学生承担责任；（3）用不同的例子扩展讨论。本文的结尾对PBL的教师和研究人员具有启示意义。