Model-based reasoning in the physics laboratory: Framework and initial results

[This paper is part of the Focused Collection on Upper Division Physics Courses.] We review and extend existing frameworks on modeling to develop a new framework that describes model-based reasoning in introductory and upper-division physics laboratories. Constructing and using models are core scientific practices that have gained significant attention within K–12 and higher education. Although modeling is a broadly applicable process, within physics education, it has been preferentially applied to the iterative development of broadly applicable principles (e.g., Newton’s laws of motion in introductory mechanics). A significant feature of the new framework is that measurement tools (in addition to the physical system being studied) are subjected to the process of modeling. Think-aloud interviews were used to refine the framework and demonstrate its utility by documenting examples of model-based reasoning in the laboratory. When applied to the think-aloud interviews, the framework captures and differentiates students’ model-based reasoning and helps identify areas of future research. The interviews showed how students productively applied similar facets of modeling to the physical system and measurement tools: construction, prediction, interpretation of data, identification of model limitations, and revision. Finally, we document students’ challenges in explicitly articulating assumptions when constructing models of experimental systems and further challenges in model construction due to students’ insufficient prior conceptual understanding. A modeling perspective reframes many of the seemingly arbitrary technical details of measurement tools and apparatus as an opportunity for authentic and engaging scientific sense making.

Figure 1

Key components of a well-defined model include articulation of a target system, assumptions, key principles, and external representations.

Figure 2

The modeling framework describes a process that includes constructing models of the measurement tools and physical system, making predictions, making measurements, interpreting measurements using the measurement model, comparison between predictions and measurements, and several pathways for revision of the models and apparatus. The labels in italics correspond to key facets of modeling that are also coded in the think-aloud laboratory activities (see Figs. 5 and 6). The model construction phases shown in the top right and top left align with the key components of models shown in Fig. 1. Color is used in the diagram to highlight the distinct phases of the modeling process and to highlight the symmetry between the modeling process for the measurement tools and physical system.

Figure 3

Written prompts used for the think-aloud experimental activity.

Figure 4

Laboratory bench used for the think-aloud experimental activity.

Figure 5

Comparisons of student activity related to the measurement tools vs physical system for three students. Each of the three students spent more time using and modeling the measurement tools.

Figure 6

Detailed view of Student $A$’s modeling codes throughout the laboratory activity. Darker shades are modeling activities specific to the measurement tools. Lighter shades are modeling activities related to the physical system.