The use of Socio-scientific Issues (SSI) in science education aiming at fostering critical thinking and decision-making capacities is known to develop the quality of students’ socio-scientific arguments. Teachers scaffolding has been shown to be important for the quality of students’ reasoning. Although students’ untutored socio-scientific discussions are recognized as important for reasoning quality, little is known about these interactions among peers. Such information is crucial for further development of teachers’ scaffolding. The aim of this study is to explore the underpinnings of student discussions on SSI in order to develop understanding for key aspects with importance for the faith of students’ decision-making conversation. Data were transcribed discussions from 4 groups of Swedish high-school students discussing “Wolves in Sweden and biodiversity”. Our theoretical framework builds on Dewey’s notion of Open-mindedness and Bernstein’s communication codes. Students’ inputs interrupting or re-vitalizing conversations were coded as Open-minded/Close-minded (OM/CM) and Elaborated/Restricted code (Ec/Rc) and their functions interpreted. In some utterances (Morals and Agitational talk) the use of Ec were found to interrupt or narrow the conversation. CM utterances (Morals and Opinions) typically interrupted conversation, something that has to be counteracted by teachers by encouraging students’ Open-mindedness in order to promote a multifaceted informal socio-scientific discussion.