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I recently read through a study published in The Journal of General Internal Medicine on the different ways that African-American and white doctors communicate nonverbally with older patients, and I was reminded of a former colleague, a specialist in brain tumors who stood out from the rest of us young doctors for two reasons.

First, though a relative newcomer to the hospital, he had diagnostic skills equal to those of physicians many years his senior. Second, and not unusual for over a decade ago, he was one of the few African-American physicians there.

One day I asked him to see one of my patients who had recently been given a cancer diagnosis. The patient, who was older and white, was sitting upright in his bed, surrounded by his wife and children, when we entered the room. But by the time we left, the patient, along with his relatives, was doing exactly what I was — leaning over and politely straining to hear what my colleague was saying.

This brilliant doctor’s soft baritone voice was rendered even less comprehensible because he tilted his head down and spoke not toward us but at the door. Every so often he looked up and shared a radiant, even reassuring smile. But then he would look down again, shift his weight and continue speaking too softly to be intelligible.

What puzzled me was that I didn’t normally think of this colleague as being that self-effacing. But when I described his visit a couple of days later to another colleague, a mutual friend, she immediately recounted a similar episode. “It’s weird, isn’t it?” she said. “He’s the smartest doctor in the hospital, but when he starts talking to some patients, it’s like he’s trying to disappear.”

For nearly two decades, teaching good communication skills has been mandatory for medical schools because of research showing that good patient-doctor communication can lead to improved patient satisfaction and better health care outcomes. To this end, medical educators have developed a host of communication courses and workshops that combine lectures, self-assessments, video recordings and “standardized patients,” or actors in the role of patients.

More recently, many schools have broadened their courses to include “cultural competency,” or the ability to communicate with those from different racial, ethnic and social backgrounds. Studies have shown that while a patient’s race and ethnicity can be linked to sharply different treatment courses and quality, better communication between doctors and patients of different backgrounds can reduce the disparities.

Despite these tremendous efforts, there is one area of communication to which few schools have devoted significant time or resources: body language and facial expressions.

Now a small but growing body of research is revealing that the nonverbal component of the patient-doctor interaction — the subtle gestures, body positions, eye contact, touch and expressions that pass between individuals — is as critical a part of communication as verbal expressions. And nonverbal cues may, in fact, be more reflective of the biases faced by doctors and patients.

In this recent study, for example, a group of medical sociologists analyzed the interactions between 30 primary care doctors and more than 200 patients over age 65 and found that white physicians tended to treat older patients similarly, regardless of race. Black physicians, on the other hand, often gave white patients contradictory signals, mixing positive nonverbal behaviors, like prolonged smiling or eye contact, with negative ones, like creating physical barriers by crossing the arms or legs.

The finding was reminiscent of earlier studies on interactions between female doctors and male patients, in which the doctors tended to give the patients conflicting nonverbal cues, combining, for example, smiles with a negative or anxious tone of voice. These mixed signals, said Irena Stepanikova, the lead author of the recent study and an assistant professor of sociology at the University of South Carolina in Columbia, are a result of dealing with “a status in our society that is devalued.” Rather than being expressed explicitly, biases regarding race and gender tend to be expressed “in behaviors not consciously controlled,” she said.

The researchers also found that despite the contradictory cues, the black doctors were generally more skillful in using positive nonverbal behaviors than their white colleagues. They were, for example, better able to use prolonged eye contact, more open body positions, facial expressions and even light touch to encourage patients and convey respect, understanding, availability and attention. “Patients feel vulnerable and search for nonverbal cues,” Dr. Stepanikova noted. “If the doctor nods when the patient is talking but keeps looking at the chart, the patient will wonder if the doctor is really taking her seriously.”

Dr. Stepanikova and her colleagues believe that greater emphasis on nonverbal communication can help medical educators address some of the social biases that affect patient care. But they acknowledge that the process will be challenging. Research in this area is still relatively sparse, and few medical educators are well versed in this topic. Moreover, even experts like Dr. Stepanikova, who needed to devote several hours to analyzing just portions of a single patient-doctor visit, are unsure of how researchers and educators can measure the nuances and complexities of nonverbal communication accurately, consistently and efficiently.

“We all want to be as egalitarian as possible,” Dr. Stepanikova said. “But what is difficult is knowing what and when to change, because so much of nonverbal communication happens outside of our conscious awareness.”