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When Races Interact, Bodies React, Purdue Study Finds

August 4, 1998
Purdue University
In the search to understand race relations in this country, two Purdue University researchers are finding the answers are more than skin deep.

WEST LAFAYETTE, Ind. -- In the search to understand race relations in this country, two Purdue University researchers are finding the answers are more than skin deep.

Scott Vrana and David Rollock, both associate professors of psychological sciences, conduct studies looking at interactions between persons of different races and genders. In a study published in the July issue of the journal Psychophysiology, the two measured physical body reactions to encounters involving whites and African-Americans.

They found that how the body reacts varies across genders and races.

"People may think they feel comfortable with a person of another race, but their body's initial physical reaction to that person may tell a different story," Rollock says.

For instance, when any stranger enters the room, most people experience an increase in heart rate. The researchers found that when the stranger is of another race, the heart rate generally goes up more than it would if the person were of the same race. The increase is most pronounced in men, and there is one exception to the different-race rule -- the presence of an African-American man sets hearts racing in both black and white men.

"We found that for white males, heart rates went up almost 10 beats per minute when a black man entered the room," Vrana says. "This is a really large change." Heart rates in this instance stayed elevated throughout the encounter.

He says black males also showed a higher heart rate in reaction to other black males, though the increase was not nearly as great -- only about two beats per minute. Heart rates decreased about two beats per minute in black males when the interactor was a white male.

Rollock says the researchers are not certain why the sight of a black man would have such a profound effect. "It could be that people are just not used to seeing African-Americans in some settings," he says. The researchers also suspect that stereotyping and negative media portrayals may also have an effect.

They conducted the study on the Purdue campus with 105 undergraduate male and female students -- 54 black, 51 white. Each subject was left alone in a room after being hooked up to equipment that monitored heart rate, perspiration and facial movements.

During the session, a stranger would walk into the room, introduce himself or herself and then proceed to take the participant's pulse. The person would say that they were doing it to make sure that the equipment was functioning properly. After one minute, the person would leave the room. Sometimes the interactor was of the same race as the participant, other times not.

The researchers conducted these experiments only with interactions between persons of the same sex. Different-sex pairings might have made the results even more complex to interpret, they say.

In addition to heart rate changes, facial expressions were another tell-tale indicator.

Vrana says Americans are a society of smilers. "Smiling when you greet someone is not inevitable, it's just something that we as a culture have chosen to do and train our children to do," he says. In other cultures, smiling isn't necessarily frowned upon, but it certainly is not the norm.

In the study, participants tended to follow the cultural norm and smile during the first 10 seconds after someone walked into the room and greeted them. During those 10 seconds, the smile was greater to someone of the same race. During the next 20 seconds, participants tended to smile longer and show a greater smile to persons of a different race.

"This might represent an automatically elicited greeting response that changes over time to a more consciously controlled expression," Vrana says. "Once people recognize that someone is of another race, they may make a conscious effort to smile at them. It may be that we are more self-conscious of how we present ourselves to people who are different from us."

After initial reactions, whites and women as a group tended to smile more throughout the interaction period than did African-Americans, who were more neutral in expression.

While the various body reactions may at times be only subtle -- such as a slight increase in heart rate or a slightly longer smile -- that doesn't mean they don't affect social relations. For instance, facial expressions are important regulators of social intercourse, the researchers say, and can significantly affect the emotional tone of those interactions. "Physical reactions to race are a factor and may require more study to understand," Vrana says.

Sources: Scott Vrana, (765) 494-6977; e-mail,

David Rollock, (765) 494-6996; e-mail,

Writer: Beth Forbes, (765) 494-9723; e-mail;

Purdue News Service: (765) 494-2096; e-mail,

ABSTRACT Physiological response to a minimal social encounter: Effects of gender, ethnicity and social context Scott R. Vrana and David Rollock

This study examined physiological response to an encounter with and touch by an unfamiliar person. Fifty-four African-American (24 male, 30 female) and 51 white (23 male, 28 female) undergraduates participated. A black or white interactor entered the room, introduced him/herself, checked equipment for 30 seconds, then took a pulse for 30 seconds. Entry of the interactor resulted in increased corrugator ("frown") and zygomatic ("smile") facial muscle activity (EMG), a skin conductance response (SCR), and heart rate (HR) acceleration. Corrugator EMG was greater among black subjects; white subjects responded with more zygomatic EMG, a larger SCR, and greater HR acceleration. Women evidenced a more positive facial expression than did men. Being touched reduced EMG and HR, but resulted in a larger SCR. White males and black males showed more HR acceleration and blood pressure increase when encountering a black male interactor.

Editor's Note: The original news release, with photo and contact links, can be found at

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Purdue University. "When Races Interact, Bodies React, Purdue Study Finds." ScienceDaily. ScienceDaily, 4 August 1998. <>.
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