This article is from the archive of our partner National Journal

In a physical sense, flags are just patterns of colored cloth: simple, geometric configurations that fly in the wind. But in a psychological sense, they are much, much more than that.

A flag is a symbol of a group identity. It is something we can own and display, as to tell others, "This is a part of who I am." The symbols on a flag instantly conjure a people's history and represent their ideas. We value those symbols greatly, because we value ourselves.

For many, the symbol of the Confederate flag stands for the legacy of black oppression in the South, a reminder of the worst chapters in American history.

When South Carolina Governor Nikki Haley signed a bill Thursday to remove the Confederate battle flag from the grounds of the statehouse, the move was more than symbolic. Flags hold a psychic power over people. When we see them, the ideas and groups they represent make a mark on our minds and can change our behavior.

When the flag near the South Carolina Legislature is taken down Friday, that power will be removed with it.

This idea was put to the test in a 2008 experiment that coincided with the presidential primaries. The question: Would exposure to the Confederate flag make people less willing to vote for Barack Obama?

It did. "White participants exposed to the Confederate flag expressed lowered willingness to vote for Barack Obama relative to control participants," the study concluded. It only took a 15 millisecond flash of the battle flag on screen to nudge people in this direction (a control group did not see the flag).

It isn't the case that the image of the flag takes open-minded people and turns them into blind-hating racists. The effects are subtler than that, activating the implicit stereotypes against black people that most people harbor.

"We argue that the concepts associated with the Confederate flag, such as racist behavior and negativity toward blacks, become accessible in people's minds when they are exposed to the flag," the study's authors write.

When thoughts are more easily accessed, they are then more likely to influence our behavior. "These little contextual cues may shift people's thoughts in a way that they interpret something more in line with what that symbol stands for," Markus Kemmelmeier, a social psychologist at the University of Nevada who has studied the influence flags have on thoughts, explains.

The psychological power of the flag stretches beyond the evaluation of politicians. It may even influence everyday interactions.

The authors of the Obama study ran the experiment a second time, but instead of asking people to judge politicians, they asked participants to judge a hypothetical black man named Robert who refused to pay rent to his landlord until the landlord conducted repairs. In this experiment, half the participants came across a folder with a small Confederate flag sticker on it; the researchers told them someone must have accidentally left it in the room.

When participants were in a room with a Confederate flag, they rated Robert more negatively when asked about how kind Robert was, how aggressive he was, how selfish, and so on.

(Exposure to the American flag changes people too. Kemmelmeier is the coauthor of a 2008 paper that found that sitting in a room where an American flag is hanging increases a sense of nationalism.)

Let's extrapolate the findings of the previous study into the real world. When a white person sees the Confederate battle flag near the South Carolina Statehouse, it's possible that their next interaction with, or judgment toward, an African-American will be slightly more negative. Perhaps they'll go a little extra out of their way to avoid walking near a black man on the sidewalk. Or maybe they'll be more hesitant when a black man approaches to ask for directions.

"What happens when we observe these subtle acts of racial bias?" ask researchers from Harvard, Princeton, and the University of California (Berkeley) in a new paper. The answer, in short, is that we become slightly more biased ourselves. Acts of racism may be contagious.

"Racial bias can be toxic," the authors write. "Merely observing a biased person express subtle negativity toward a black person may be enough to shift our own racial bias." Their current work is based of a body of research suggesting that behaviors and emotions can be contagions: We tend to act more dishonest around dishonest people, happier around happy people, etc.

In their experiment, participants were either shown a video of a white person treating a black person fairly, or a video of a white person exhibiting subtle racist gestures (not maintaining eye contact, exhibiting hesitant body language). After watching the videos where the black person was treated less fairly, participants also indicated they would be less inclined to make friends with the black person depicted in the video, and they rated hypothetical black men more negatively.

It's possible, then, that the removal of Confederate flags can have a multiplier effect, removing a racial-bias instigator that may propagate itself in the form of thousands of micro-aggressive racist acts.

Kemmelmeier says those who see the Confederate flag as a symbol of Southern heritage are bound to feel personally attacked when the flag is removed. "When that symbol is taken down, to many it feels like an attack of a whole way of life," he says.

But yet he senses a shift in the way people perceive the symbol of the flag. There have always been dueling interpretations: that the flag either stands for heritage, or that it stands for hate. When the Charleston church shooter proudly wore the symbols of the Confederacy as symbols of hate, it became harder to deny that interpretation. "The dual meaning that could coexist was no longer possible," he says.

This article is from the archive of our partner National Journal.