Our results challenge current policy and law advocating instructional advance directives as a means of honoring specific patient wishes at the end of life. Future research should explore other methods of improving surrogate decision making and consider the value of other outcomes in evaluating the effectiveness of advance care planning.

To honor the wishes of an incapacitated patient, surrogate decision makers must predict the treatment decisions patients would make for themselves if able. Social psychological research, however, suggests that surrogates' own treatment preferences may influence their predictions of others' preferences. In 2 studies (1 involving 60 college student surrogates and a parent, the other involving 361 elderly outpatients and their chosen surrogate decision maker), surrogates predicted whether a close other would want life-sustaining treatment in hypothetical end-of-life scenarios and stated their own treatment preferences in the same scenarios. Surrogate predictions more closely resembled surrogates' own treatment wishes than they did the wishes of the individual they were trying to predict. Although the majority of prediction errors reflected inaccurate use of surrogates' own treatment preferences, projection was also found to result in accurate prediction more often than counterprojective predictions. The rationality and accuracy of projection in surrogate decision making is discussed.

Very few individuals may desire the standard approach to advance care planning whereby preferences for specific life-sustaining treatments are documented and these requests are strictly followed near death. Instead, patient autonomy may be better served by emphasizing discussion of process preferences and leeway in decision making.

Preferences for life-sustaining treatment are dependent on the context in which they are made, and thus individuals may express different treatment preferences when they are healthy than when they are ill. These results challenge a key psychological assumption underlying the use of instructional advance directives in end-of-life decision making.