• scientific reasoning;
  • epistemological commitments;
  • prior knowledge;
  • hydrostatics


Reasoning skills are major contributors to academic and everyday life success. Epistemological commitments (ECs) are believed to underlie reasoning processes and, when considered, could do much in delineating the complex nature of scientific reasoning. This study examined the relationship between ECs and scientific reasoning among college science students. Prior knowledge (PK) was factored in as an intervening variable. Participants were 139 college students enrolled in two physics courses in a large Midwestern university. They completed an online questionnaire, which assessed their PK regarding buoyancy in liquids and EC to the consistency of theory with evidence. Responses to the online questionnaire were used to select 40 participants with varying levels of PK and EC. These participants were divided into four groups, each with 10 students, representing four conditions: High PK–High EC, High PK–Low EC, Low PK–High EC, and Low PK–Low EC. These groups allowed using a 2 × 2 factorial quasi-experimental design to examine the relationship between participants' reasoning and ECs, accounting for their PK. The quality of participants' reasoning was assessed during individual interviews, which presented them with four problem-solving tasks involving objects immersed in water. Two-way analysis of variance (ANOVA) indicated the absence of interaction between PK and EC. The results showed that the higher the ECs were, the higher the quality of reasoning was for comparable levels of PK. Additionally, it was found that PK impacted reasoning more strongly when ECs were weaker. © 2010 Wiley Periodicals, Inc. J Res Sci Teach 47: 1064–1093, 2010