What does validating a variable representation assessment tell us about how introductory chemistry and geology students use multiple external representations?

A key challenge for students in science classrooms is learning how to use multiple external representations (MERs) properly; when the information depicted by a representation is misunderstood, or understood correctly but misapplied, students can make improper conclusions and predictions when problem-solving. To better understand students’ rationale when interacting with MERs, 16 chemistry and geology undergraduates from a large public research university in the midwestern United States completed a card sorting activity. The activity asked each student a set of discipline-specific questions. For each question, they were given a set of 15 note cards depicting different representations and asked to select any pertinent representations for the question. As representations were selected, participants explained aloud their rationale for each. A mixed-methods analysis of the activity revealed that participants from each discipline used a standard set of five reasons for using representations: recall, visual, discipline-specific knowledge, pairing-up, and compare-and-contrast. Descriptions of each reason, along with how their usage compared between chemistry and geology students, are shared. The results from these activities suggest improvements that can be made to the assessment of students’ knowledge of MERs.