Unconscious racial biases can influence the treatment decisions doctors make, according to the results of a study released last month by researchers in the Psychology Department and at Harvard Medical School.

The study aimed to investigate whether the well-known racial disparities in heart attack treatments were the result of bias or some other factor—a lack of treatment options for hospitals frequented by blacks or individual patient preference, for example.

The fact that black patients experiencing heart attacks were far less-likely to receive a key blood clot-busting procedure called thrombolysis has been known for some time, but the new study determined that there exist distinct “pro-white, anti-black” race biases, according to study co-author Alexander R. Green, a doctor at Massachusetts General Hospital and a lecturer at Harvard Medical School.

The recent study, which was published in an online edition of the Journal of General Internal Medicine, asked over 200 mostly white resident physicians to prescribe treatment to hypothetical patients based only on a picture of a man’s face and a description of the patient’s sharp chest pain. All of the hypothetical conditions were the same, except for the fact that some of the men were white and others were black. A great deal more of the physicians prescribed thrombolysis for the white men than did for the black men.

“For the most part, other people who had been studied using these relatively new cognitive tests showed race biases,” Green said. “We suspected that we would find unconscious biases in resident physicians, because they are people like everyone else.”

Green said that while the study reveals bias regarding the prescription of treatment, it’s unclear whether the administration of that treatment would be affected by those biases.

Cabot Professor of Social Ethics Mahzarin R. Banaji, an expert in the field of bias study who has developed tests to measure bias in the past, said it’s no surprise that physicians are susceptible to bias in their work.

“The most profound experience I’ve had while doing this research is that I have discovered that the biases that we’ve discovered in other people lie in my own mind, too,” Banaji said. “It really brings about an enormous humility...it’s something that brings understanding and realization—that people who don’t intend to do harm might still be doing so.”

Banaji also said that while “race is one of the biggest biases,” her previous work has shown prominent social biases based on class, age, appearance, and “the foreignness of a person.”

Green said the reason for such differences in bias is largely cultural.

“It’s the culture’s thumb print in our minds,” Green said. “If you’re raised in this country in a certain social group, with certain media, your mind is conditioned in a certain way. You may be able to override that conditioning, but the bottom line is that those subconscious connections are very deep in our minds, whether we want them to be there or not.”

But unlike most species, Banaji said, human intelligence allows for an ability to correct for those biases.

“Human beings have a capacity that has got to be the envy of every chimpanzee, and that’s the ability to look inside our minds and see what’s there, and this is a nice case of something like that,” she said. “If doctors who do not wish to have bias in their treatment would like to fix that particular behavior, then I’d say we have access to becoming aware of it and watching our social interactions carefully.”

—Staff writer Malcom A. Glenn can be reached at mglenn@fas.harvard.edu.