This study examined the effectiveness of three instructional and assessment strategies on conceptual understanding of the DNA molecule. Specifically, a model building task was utilized to determine if physical model construction, digital model construction with a touchscreen tablet computer, or paper worksheet activity effected conceptual understanding during the initial exposure to an abstract science concept. The DNA molecule was chosen as an exemplary three-dimensional, abstract concept with physical and digital model building interventions. Conceptual understanding was measured using an objective quiz, a drawing of a DNA molecule, and a hand-written explanation of DNA. Conceptual understanding was measured immediately after intervention and again two months later. The study examined effects to conceptual understanding of model building by comparing physical models constructed using foam pieces and digital models constructed using a touchscreen tablet computer. A control group completed a paper worksheet activity on the topic of DNA.

In all conditions, an instructional video about DNA was used to standardize the content taught. To account for the potential covariates of spatial ability and attitudes to scientific inquiry, participants completed a mental rotation test to measure spatial ability and an attitudes to scientific inquiry survey. A total of 161 students across six intact 9th-grade Living Environment classrooms participated in the study. The results from the three conceptual understanding measures were compared among the three groups at both immediate and delayed post-test timepoints as well as across the two post-test timepoints. For both immediate and delayed post-test, there were no differences among the groups for the objective quiz measure. However, the physical model group outperformed the digital model and control groups in both the drawing and explanation measures at both timepoints (p < 0.01). Across the two timepoints, the control group showed a significant degree of forgetting for the objective quiz measure (p < 0.001) and the digital group demonstrated a significant degree of forgetting for the objective quiz measure (p = 0.03) and drawing measure (p < 0.001).

There was a significant difference between the delayed post-test and pre-test of the objective quiz for the physical model group (p < 0.001) and no significant difference between the post-test and delayed post-test for the objective quiz for the physical model group suggesting long-term conceptual understanding and retention. Overall, the physical model group demonstrated greater conceptual understanding at immediate and delayed timepoints for the drawing and explanation measures as well as significant retention of conceptual understanding of DNA as measured by the objective quiz across three timepoints. The digital model group demonstrated a greater degree of forgetting for objective quiz and drawing measures as well as underperformed in the three conceptual understanding measures at both post-test and delayed post-test timepoints. This suggests that the greater degree of physical, haptic manipulation of a three-dimensional model aids in conceptual understanding at all three measures as well as long-term memory when compared with the limited haptic interactions with a two-dimensional touchscreen device.