Purpose: Experts question whether certain decision-making biases are caused by low literacy. In this study, we explore whether decision-making biases are caused by low literacy per se, or if these biases can instead be explained by larger cultural factors, which are related to both literacy and patients’ medical beliefs.
Method: 574 men were recruited for a study about prostate cancer decisions. All of the men were undergoing prostate biopsies following a high PSA test. As a part of a larger questionnaire, each patient was asked to respond to a hypothetical cancer scenario. They were asked to choose between having surgery and accepting a 10% chance of dying from cancer, versus not having surgery (watchful waiting) and accepting a lower, 5% chance of dying from cancer. Past research has shown that a surprising number of people (~60%) choose the dominated surgery in this scenario. Just prior to this scenario, participants’ literacy (REALM) and numeracy (Subjective Numeracy Scale) were assessed. Patients were also asked questions about their beliefs about cancer treatment. These questions specifically assessed the patients’ bias toward active treatment options (e.g. “How important is it to treat cancer, whether or not it makes a difference in survival?”).
Result: 65% of the patients chose the dominated surgery option. As expected, participants who choose the dominated option were significantly lower in literacy than participants who chose the more rational treatment option (p < .01; numeracy did not predict choice, p > .10). However, the relationship between literacy and choice was mediated by participants’ desire for more active treatment. That is, literacy was not related to choice when controlling for participants’ desire for active treatment.
Conclusion: In the present scenario, the proximate cause of irrational decision making was patients’ desire for active treatment, rather than low literacy per se. Literacy predicted patients’ tendency to choose the dominated option, but only because literacy was related to general attitudes about active treatment. These data suggest that attempts to improve patient comprehension will not be successful at debiasing those patients. The fact that low literacy is related to preferences for active treatment suggests that there may be larger cultural factors at work that cause the present decision bias.