And as those difficult experiences add up, many turn more to supernatural, or religious, explanations as they age.
"Plenty of studies document that," Legare said. "Churches are full of older people. There are many different explanations for that, of course, but I think a tendency to endorse supernatural explanations increases as we age."
The research in South Africa focuses tightly on how that tendency is affected by local culture, particularly when death from a horrible disease comes so frequently.
Nearly everyone in South Africa has been affected in a "catastrophic" way, either by contracting the disease, losing a loved one to AIDS, or being orphaned as a young child when both parents die of AIDS.
"I spent a lot of time in the hospitals," Legare said. "There's a flood of people coming in. When they learn they have AIDS they will typically sit down with a nurse practitioner who will say there are treatments available but unfortunately we don't have the resources to provide you with those treatments. You go home, try to eat healthy food (where unemployment is more than 70 percent in some areas) and enjoy the rest of your short life.
"This is what people are told. If someone told me that, I would want another solution. I would say I don't want to go home and die without trying. I want to look for other options."
Belief in supernatural powers, whether it's witchcraft or religion, "provides people with a sense that there's someone out there who knows what's going on, there's some way to intervene. This is why prayer is so therapeutic for so many people."
Of course, just because something is therapeutic doesn't prove it's true.
"I am making absolutely no claim about the objective reality of any religion," she said.
But one thing she said she knows passionately: The people of an AIDS-ravaged country feel they've lost control of their surroundings, and they look for answers to some of life's toughest questions.
Why me? Maybe the witch did it. Or maybe not.
"There are many things that are useful to us that aren't true," Legare said.