Moreover, those who held false beliefs often rated black patients' pain as lower than that of white patients and made less appropriate recommendations about how they should be treated.
The study, published in the Proceedings of the National Academy of Sciences, could help illuminate one of the most vexing problems in pain treatment today: That whites are more likely than blacks to be prescribed strong pain medications for equivalent ailments.
A 2000 study out of Emory University found that at a hospital emergency department in Atlanta, 74 percent of white patients with bone fractures received painkillers compared with 50 percent of black patients. Similarly, a paper last year found that black children with appendicitis were less likely to receive pain medication than their white counterparts. And a 2007 study found that physicians were more likely to underestimate the pain of black patients compared with other patients.
Researchers who study health disparities have said that unconscious stereotypes about African Americans likely contribute to this problem, as well as physicians' difficulty empathizing with patients whose experiences differ from theirs.
The University of Virginia study buttresses arguments that physician bias is a factor. Its research had two parts: One looked at a random sample of 92 whites from across the country. The second queried 222 white medical students and residents at the university and elsewhere. In both cases, participants were given a series of statements that contained accurate or inaccurate information about the biological differences between blacks and whites.
"We were expecting some endorsement" of the false beliefs, said Kelly Hoffman, a U-Va. doctoral candidate in psychology who led the study. But she said the researchers were surprised so many in the group with medical training endorsed the false beliefs, some of which she called "more outlandish."
For example, 58 percent of the study's general group said they believed that "blacks' skin is thicker than whites'." About 40 percent of first- and second-year medical students also thought that was true, as did 25 percent of residents -- doctors who recently completed their studies and now are receiving more specialized training.
Also surprising was that so many of the students and new physicians did not believe true statements about biological differences between the races, Hoffman said. For example, only half of residents knew that whites are less susceptible to heart disease than blacks.
The medical group was given one extra test. After reading brief case studies of two patients in pain, one white and one black, the students and physicians were asked to rate each individual's pain as well as make treatment recommendations. The researchers then compared the results with recommendations from 10 experienced physicians who had analyzed the case studies without any racial information included.
"What we found is those who endorsed more of those false beliefs showed more bias and were less accurate in their treatment recommendations," Hoffman said.