This study examined the impact of two epistemic commitments on the quality of college
students‟ scientific reasoning in the domain of hydrostatics. These were the commitment
to the consistency of theory with prior knowledge and commitment to the consistency of
theory with evidence. Participants were 12 sophomore science majors enrolled in a large
Midwestern university in the United States. They were first administered a 10 short-answer
item questionnaire to assess their understandings of buoyancy, and then participated in an
individual, think-aloud interview centered on four paper-and-pencil scenarios involving
systems of objects immersed in water. During the interview, participants also were asked
to justify their responses and explain certain reported “observations” in each scenario. The
interviews aimed to explore the impact of participants‟ epistemic commitments on their
reasoning. A majority of participants did not demonstrate coherent reasoning schemes
when working with buoyancy problems. To be sure, participants‟ prior conceptions of
buoyancy interacted with the target epistemic commitments in impacting their reasoning.
Still, there was a discernable impact for the target epistemic commitments on the quality
of participants‟ reasoning.