Should we scaffold it? Analysing the effect of task format and scaffolding on students’ learning gain

Abstract

An essential goal of science education is to support students in reasoning about the underlying mechanisms of observed phenomena, which requires well-designed instructional approaches. In organic chemistry, various approaches have been designed to support students’ reasoning about mechanisms, including contrasting cases as a task format. Qualitative studies indicate that contrasting cases positively impact students’ mechanistic reasoning since this task format encourages students to identify and analyse similarities and differences in chemical phenomena. Additionally, a prior mixed-methods study showed that scaffolded contrasting cases can advance undergraduate students’ reasoning about mechanisms, but the effect varied depending on prior knowledge. Despite these valuable insights, research has not yet quantitatively analysed the effectiveness of scaffolded versus non-scaffolded contrasting cases, compared with single cases. This study quantitatively examines the effects of these instructional approaches on undergraduate organic chemistry students’ learning gains, with a particular focus on the role of prior knowledge. Our findings suggest that non-scaffolded contrasting cases increase learning gains for students with low prior knowledge. Additionally, scaffolded contrasting cases support students with low prior knowledge in their open-ended reasoning about chemical mechanisms. Given these findings, organic chemistry instructors should consider contrasting cases as an alternative task format. However, instructors should introduce the scaffolding used in this study with practice sessions as it may otherwise increase cognitive load for students unaccustomed to its demands.