Understanding science with citizen science: A randomized controlled field trial investigating the efficacy of a soil science intervention for promoting children's scientific reasoning

Scientific reasoning is a key 21st century skill and a central goal of science education. Citizen science projects build on inquiry-based learning and actively involve students in genuine scientific research. In this study, we investigated the efficacy of a newly developed extracurricular citizen science (CS) intervention for elementary school students who were enrolled by their teachers in an extracurricular STEM enrichment program for talented students in southwest Germany. Students participated in a CS project that was embedded in an 8-week inquiry-based science course in the field of soil science. We ran a preregistered multisite randomized controlled field trial with pre- and posttest measures. Data were collected from N = 98 third- and fourth-grade participants. Multiple linear regression analyses controlling for pretest scores indicated that students in the intervention group acquired better experimentation skills, more sophisticated views of CS, and more comprehensive knowledge about the topic of soil compared with students in the waitlist control group. Furthermore, positive effects were found on a multiple-select score (but not the full-scale score) assessing an advanced understanding of the quality criteria of experimental designs. No effects were found for a measure assessing epistemic beliefs as well as a number of motivational outcomes. These findings highlight the potential of combining CS and inquiry-based learning to foster domain-specific components of scientific reasoning in early science education.