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Socially relevant geoscience topics may be difficult for students to learn. For example, connecting hydraulic fracturing to Midwestern US earthquake swarms and using the fossil record to infer past Earth environments may challenge students because of their prior exposures to nonscientific explanations. Sociocognitive theoretical perspectives based on decades of developmental and educational psychology, as well as science education research posit that students may have particular difficulty in evaluating the connections between lines of scientific evidence and explanations. This challenge is especially daunting when students are confronted with various alternative explanations (e.g., scientific and nonscientific explanations). In the present study, we compared two types of scaffolds designed to facilitate Mid-Atlantic middle school students’ (N = 40) scientific thinking and learning about controversial geoscience topics when confronted with alternative explanations. In a less autonomy-supportive scaffold, participants were given four lines of evidence and two explanatory models, one scientific and one nonscientific. (Fracking; Supplementary Materials 1 & 2); in a more autonomy-supportive scaffold, students chose four of eight lines of evidence and two of three explanatory models, one scientific and two nonscientific (Fossils; Supplementary Materials 1 & 2). Quantitative analyses revealed that both activities facilitated students’ evaluations in shifting students’ judgments toward the scientific and deepening their knowledge, although the more autonomy-supportive activity had greater effect sizes. Structural equation modeling suggested that more scientific judgments related to greater knowledge at post-instruction for the more autonomy-supportive scaffold. These activities may help students develop more scientific evaluation skills, which are central to understanding geoscience content and science as a process. 

Students often encounter alternative explanations about astronomical phenomena. However, inconsistent with astronomers’ practices, students may not be scientific, critical, and evaluative when comparing alternatives. Instructional scaffolds, such as the Model-Evidence Link (MEL) diagram, where students weigh connections between lines of evidence and alternative explanations, may help facilitate students’ scientific evaluation and deepen their learning about astronomy. Our research team has developed two forms of the MEL: (a) the preconstructed MEL (pcMEL), where students are given four lines of evidence and two alternative explanatory models about the formation of Earth’s Moon and (b) the build-a-MEL (baMEL), where students construct their own diagrams by choosing four lines scientific evidence out of eight choices and two alternative explanatory model out of three choices, about the origins of the Universe. The present study compared the more autonomy-supportive baMEL to the less autonomy-supportive pcMEL and found that both scaffolds shifted high school student and preservice teacher participants’ plausibility judgments toward a more scientific stance and increased their knowledge about the topics. Additional analyses revealed that the baMEL resulted in deeper evaluations and had stronger relations between levels of evaluation and post-instructional plausibility judgements and knowledge compared to the pcMEL. This present study, focused on astronomical topics, supports our team’s earlier research that scaffolds such as the MELs in combination with more autonomy-supportive classrooms may be one way to deepen students’ scientific thinking and increase their knowledge of complex scientific phenomena.