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College biology courses commonly use diagrams to convey information. These visual representations are embedded in course materials with the expectation that students can comprehend and learn from them. Educational research, however, suggests that many students have difficulty understanding diagrams and the conventions (e.g., labels, arrows) they contain. The present study evaluates biology students’ ability to comprehend scientific diagrams and the diagram characteristics that affect this comprehension. Participants were students in a physiology course who completed a multiple-choice test of diagram comprehension ability (DCA) (Cromley JG, Perez TC, Fitzhugh SL, Newcombe NS, Wills TW, Tanaka JC. J Exp Educ 81: 511–537, 2013). We coded the conventions used in each test diagram and used these codes to capture the diagram characteristics of conventions and complexity. Descriptive analyses examine students’ ability to understand scientific diagrams and which diagram characteristics cause the most difficulty. We also compared groups with low and high DCA scores to evaluate how students at different levels of comprehension ability are affected by diagram characteristics. Results show relatively poor DCA; the average total test score was only 69.5%. The conventions used in a diagram also affected diagram comprehension, and results show students had the most difficulty comprehending diagrams using a letter or numbering system, where arbitrary letters/numbers were used to signify objects and diagrams using cut-outs that showed cross sections and magnified interior views. Additionally, students’ comprehension was higher on diagrams with higher complexity (i.e., more types of conventions used), potentially indicating students are able to take advantage of the supports that different conventions provide. Implications for instruction are identified.

Relational reasoning, or the ability to identify meaningful patterns within streams of information, has emerged as an important factor in a variety of complex tasks. One factor that has received relatively little research attention, however, is how relational reasoning may be influenced by the representational systems (i.e., verbal or nonverbal) that hold the information about which one is reasoning. Most studies have also focused only on analogical reasoning at the expense of anomaly, antinomy, antithesis, 3 additional forms of relational reasoning. All participants in the current study, 762 undergraduate students, completed shortened versions of the Test of Relational Reasoning (TORR; Alexander, 2012) and verbal Test of Relational Reasoning (vTORR; Alexander, 2015). These 2 tests both measure each of the 4 forms of relational reasoning, but the TORR uses a nonverbal representation system and the vTORR uses a verbal system. Patterns of performance within and between these relational reasoning tests, as well as measures of linguistic and spatial ability, test the hypothesis that representational system adds explanatory value for understanding relational reasoning. Results show that the 4 form framework of relational reasoning is present in the 2 measures, both separately and combined, but representational system exerts a more powerful effect than expected. Use of the shortened measures is also supported through evidence of score reliability and validity.

Undergraduate STEM students majoring in various science sub-disciplines (e.g., chemistry, physics, engineering) must develop strong understandings of core foundational thermodynamics concepts. The ability for course instructors and researchers to effectively refine instruction and develop interventions to support students' learning hinges on their ability to accurately gauge students' knowledge through the use of established measures. The Thermodynamics Conceptual Reasoning Inventory (TCRI) is designed to gauge undergraduate students' understanding of introductory thermodynamics concepts. The present study extends the findings of a previous publication by positioning the TCRI within the broader international literature of thermodynamics concept inventories and generating an argument for the reliability and validity of TCRI scores in a broader context. Participants (n = 278) took the revised 36-item TCRI (available in the supplementary online materials). Findings revealed that TCRI scores are useful in the broader context (e.g., no evidence of floor or ceiling effects, evidence of high reliability, no differences for students across majors, and TCRI scores were moderately correlated with both course exam scores and GPA). No further revisions are recommended based on analysis of item properties. The cumulative body of evidence related to the TCRI suggests that scores are useful indicators of undergraduate students' conceptual understanding of introductory thermodynamics concepts.

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