MADISON - As a brain-damaged woman named Terri Schiavo lived her final days in 2005, her family's bitter feuding imparted a tragic lesson about the importance of specifying one's wishes for end-of-life medical treatment.

Yet, beyond headline-grabbing cases such as Schiavo's, what truly motivates people to plan for medical care at life's end" With record numbers of Americans - the Baby Boom generation - now reaching age 60, we still know surprisingly little about these decisions or the factors that shape them, says University of Wisconsin-Madison sociologist Deborah Carr.

A study by Carr and her Rutgers University colleague Dmitry Khodyakov now offers insight into a critical aspect of end-of-life planning: the choice to appoint a "health care proxy" who will make treatment decisions should a person become incapacitated. Writing in the June issue of the Journal of Health and Social Behavior, the researchers report that education, religious attitudes and experience with a loved one's death - especially a painful death - are all powerful influences on this decision.

The findings have important implications for policies and practices designed to encourage people to name a proxy, also known as a "durable power of attorney for health care" (DPAHC). Federal law currently mandates that patients entering a federally funded hospital or clinic be asked whether they have a DPAHC or a document called an advance directive. Medical personnel will also sometimes discuss the issue with patients; however, they tend to employ abstract arguments or ask patients to imagine their future state of health, says Carr.

Her study suggests instead that having people recall a loved one's death and their feelings about it may be more convincing.

"Our results speak to the power of real world experience," says Carr. "Abstractions, literature, handouts are all great. But in the end, I think people respond more to visceral, emotional factors."