Objective To determine whether increased cost sharing in health insurance plans induces higher levels of consumer sophistication in a non‐elderly population. Study design This analysis is based on the collection of survey and demographic data collected from enrollees in the RAND health insurance experiment (HIE). During the RAND HIE, enrollees were randomly assigned to different levels of cost sharing (0, 25, 50 and 95%). Methods The study population compromises about 2000 people enrolled in the RAND HIE, between the years 1974 and 1982. Effects on health‐care decision making were measured using the results of a standardized questionnaire, administered at the beginning and end of the experiment. Points of enquiry included whether or not enrollees' (i) recognized the need for second opinions (ii) questioned the effectiveness of certain therapies and (iii) researched the background/skill of their medical providers. Consumer sophistication was also measured for regular health‐care consumers, as indicated by the presence of a chronic disease. Principal findings We found no statically significant changes (P < 0.05) in the health‐care decision‐making strategies between individuals randomized to high cost sharing plans and low cost sharing plans. Furthermore, we did not find a stronger effect for patients with a chronic disease. Conclusions The evidence from the RAND HIE does not support the hypothesis that a higher level of cost sharing incentivizes the development of consumer sophistication. As a result, cost sharing alone will not promote individuals to become more selective in their health‐care decision‐making.