While most people believe they would not tolerate a racist act, a new study from Canadian and U.S. researchers found test subjects in an experiment reacted with indifference when exposed to one.

Researchers in Toronto recruited 120 non-black York University students for what they said was a psychology study. Half of the students were each put in a room with two actors — one white and one black — posing as other participants.

The black actor then left the room to retrieve a cellphone, lightly bumping the other actor on the way out. The white actor then responded in one of three ways, saying nothing, saying the phrase "I hate when black people do that" or uttering an offensive racial slur.

When the black actor returned, study participants were asked to fill out a questionnaire rating their emotional mood and then were asked to choose a partner for what they thought was the actual test.

The researchers found that in cases where the white actor made a racist comment, participants did not speak out, did not report any emotional distress and actually chose the white actor as a partner more often than the black actor.

These results stood in stark contrast to a second group of respondents who were asked who they would choose as a partner after having the situation described to them. These respondents overwhelmingly chose not to work with the white actor when a racist statement was uttered.

Lead researcher Kerry Kawakami, a psychology professor at York University, said the study raises awareness that even people who consciously condemn racism might harbour implicit biases. (listen to the CBC radio Quirks and Quarks interview with the study's lead author, Dr. Kerry Kawakami.)

"People should be aware that maybe they have this duality inside themselves," Kawakami told CBC News. "They think they're egalitarian, they think they're fair, they think they'll react in negative ways towards racism, but that might not actually be the case."

In an accompanying analysis in Science, psychologists Eliot R. Smith from Indiana University and Diane Mackie from the University of California, Santa Barbara, suggest another reason the participants may have reacted to the incident with indifference.

Since they were knowingly participating in a test, they behaved in manner previous research has suggested experiment participants often do: that is, constraining normal impulses in an effort to be helpful and focused on what they believe to be the task.

Smith said the study illustrates that in certain social contexts, it may be easy for people to dismiss a racist remark as an oddity. Those social contexts extend beyond the role of experiment participant.

"The failure of people to confront or do anything about racist comments is pretty widespread in the real world," said Smith. "People may feel uncomfortable if someone makes a remark like this, but it's rare they will actually confront them."

Researchers from the University of British Columbia and Yale University also co-authored the study.

With files from the Associated Press