Abstract: During medical visits, the stakes are high for many patients, who are put in a position to make, or to begin to make, important health-related decisions. But in such visits, patients often make cognitive errors. Traditionally, those errors are thought to result from poor communication with physicians; complicated subject matter; and patient anxiety. To date, measures to improve patient understanding and recall have had only modest effects. This paper argues that an understanding of those cognitive errors can be improved by reference to a behavioral science framework, which distinguishes between a “System 1” mindset, in which patients are reliant on intuition and vulnerable to biases and imperfectly reliable heuristics, and a “System 2” mindset, which is reflective, slow, deliberative, and detailed-oriented. To support that argument, we present the results of a randomized-assignment experiment that shows that patients perform very poorly on the Cognitive Reflection Test and thus are overwhelmingly in a System 1 state prior to a physician visit. Assigning patients the task of completing patient-reported outcomes measures immediately prior to the visit had a small numerical, but not statistically significant, shift towards a reflective frame of mind. We describe hypotheses to explain poor performance by patients, which may be due to anxiety, a bandwidth tax, or a scarcity effect, and outline further direction for study. Understanding the behavioral sources of errors on the part of patients in their interactions with physicians and in their decision-making is necessary to implement measures improve shared decision-making, patient experience, and (perhaps above all) clinical outcomes.