Although it has been suggested that people use the wrong cognitive procedures in solving stock and flow (SF) problems, we know little of what these mental procedures are. We present two experiments aimed at demonstrating the influence of analogical reasoning on SF failure. Results of Experiment 1 show that SF failure decreases when people are asked to compare problems that share behavioral similarity (common relations). However, the benefit of behavioral similarity depends on the surface similarity (common superficial object attributes). Results from Experiment 2 demonstrate that when the behavioral characteristics of the problems are unknown by the participants, the process of comparing two problems with behavioral similarity improves responses to a subsequent SF problem, regardless of the surface similarity between the problems. Surface similarity helps only when the behavioral similarity between the problems is already known. Implications for training and education in system dynamics are discussed. Copyright © 2011 System Dynamics Society.