INDIVIDUAL DIFFERENCES IN THE IMPACT OF ANECDOTAL EVIDENCE ON MEDICAL TREATMENT CHOICE

Purpose: This research tested the hypothesis that including anecdotal evidence impacts treatment choice by influencing the trade-off between effectiveness and invasiveness. In addition, the role of decision-making style was examined.

Methods:  134 participants were asked to imagine making a decision between two treatment options for Angina (chest pain).  Bypass is more effective, but more invasive; balloon angioplasty is less effective, but less invasive.  Participants received statistics about the effectiveness of the two treatments, testimonials, or both.  They then indicated their choice between the two treatment options and rated the importance of the effectiveness and invasiveness of the treatment chosen to their decision.  A subset of the participants also completed the Decision Making Styles Inventory (DMI).  The DMI describes individuals on three styles of decision-making: analytical, intuitive, and regret-based.

Results: Differences in treatment choice between groups were marginally significant, with those receiving only statistics being the most likely to choose bypass and those receiving only testimonials being the least likely to choose bypass.  Ratings of the importance of effectiveness were not correlated with treatment choice, but ratings of the importance of invasiveness were.   Those rating invasiveness as less important were more likely to choose bypass. However, ratings of the importance of invasiveness did not differ by group. Participants with higher analytic and regret based decision making style scores were more likely to choose angioplasty.  This was qualified by significant group x analytic and group x regret-based interactions. If presented with only testimonials, higher regret-based scores were linked to a greater likelihood of choosing bypass. When presented with either statistics or testimonials, those with higher analytic scores were more likely to choose bypass, but when presented with both, higher analytic scores indicated a greater likelihood of choosing angioplasty.  

Conclusions: Although the presence of anecdotal evidence changes treatment choices, it does not do so by changing the relative importance of effectiveness and invasiveness to the decision maker. However, ratings of the importance of invasiveness explain a significant amount of the variance in treatment choice.  Therefore, the trade-off between effectiveness and invasiveness appears to be an important source of individual differences in treatment choice.  In addition, this research provides some evidence that individual differences in decision-making style play a role in the impact of anecdotal evidence on treatment choice.