Students' Prioritization of Initial and Direct Causal Mechanisms During Model Evaluation

Scientific modeling is supported by epistemic criteria to evaluate the "goodness" of scientific products.A central epistemic criterion is causal mechanism which means identifying the underlying causes which generate changes within a system.During a five-week model-based inquiry unit students identified causes of the phenomenon, eutrophication, but it was unclear whether student understood the causes hierarchically, i.e., whether some causes led to others, and whether some were more critical to include in a model than others.In a model evaluation task, students prioritized a model that was complete and had all the causes, deprioritized the model missing the direct causal mechanism, and placed models missing the initial causes in the middle.The results indicate that students thought about mechanisms in terms of chaining which means students thought about how causes led to outcomes within a system.