The ability to reason proportionally is a foundational concept for students to master while in middle school, leading to increased understanding and deeper conceptualization of higher level mathematics and science in the later grades (Heller et al., 1989; Johnson, 2015; Lesh, Post, & Behr, 1988; Lobato & Ellis, 2010; Ellis, 2013; Carney et al., 2015). Yet mathematics education lacks research-based teaching strategies on developing proportional reasoning skills in middle school students. This study seeks to determine the influence that specific ratio relationships and models (diagrams) have on student thinking regarding a given proportional reasoning problem and its solution via cognitive interviews with 29 middle school students in Idaho. Results may inform teaching practices on proportional reasoning
