Accuracy and Bias in Perceptions of Spouses' Life‐Sustaining Medical Treatment Preferences1

This research investigated accuracy, projection bias, and base‐rate utilization in spouses' perceptions of end‐stage renal disease patients' preferences for life‐sustaining medical treatment in hypothetical conditions of declining health. Multilevel models revealed that spouses' perceptions were largely biased, determined by their own preferences for the patients' treatment (projection bias) and by typical treatment preferences (base‐rate utilization). Both biases, however, served as indirect routes to a modest degree of accuracy. Moreover, spouses who overestimated patients' preferences for life‐sustaining treatment and who perceived patients' preferences as consistent with their own reported higher levels of marital adjustment than did those who were less biased. Results suggest that spouses' biases in judgments of patients' treatment preferences may promote accuracy and marital adjustment functionally.