The tragic shooting took place in a black church in Charleston, South Carolina, last month -- and the following spate of burnings of black churches -- have thrust questions of racial injustice back into the center of our national dialogue.

Many Americans have been left wondering what causes racism to persist in our society, and what sort of psychological toll acts of hatred like the Charleston shooting take on members of the black community.

For answers to these and other questions, HuffPost Science spoke to Dr. Priscilla Dass-Brailsford, a psychologist at Georgetown University and the Chicago School of Professional Psychology who specializes in ethnocultural and community violence, about the science of racial injustice. Here's what she had to say.

Dr. Pricilla Dass - Brailsford

What types of psychological factors give rise to racist beliefs and behaviors?

Racism has to do with thinking of oneself as being different from other people. Racists see others as being less than, and think of themselves as being superior. Just as you would have attitudes about anything -- about poor people, for example, or immigrants -- you have to think about where those attitudes began and how they developed. Was it environmental? Was it upbringing? Was the person born that way? So, there's the age-old debate about nature versus nurture here.

Can you elaborate on some of the ways that a community or society can foster and perpetuate racism?

If you grow up in an environment where people think white people are superior to people of color, you begin to believe in it. And when your whole system around you is constructed in a way that supports that belief, you will begin to think that you are superior.

South Africa is a classic example: When you look at the country's history, everything was divided, all of the institutions. The church actually supported racism -- the white church there (the Dutch reform church) actually believed that black people were inferior and white people had to rescue and take care of them.

If you grow up in an environment where people think that white people are superior to people of color, you begin to believe in it.

That's how a belief gets constructed -- by the social environment you live in, the schools you attend, your church, your families, your neighbors. All of that.

What can learn from the example of South Africa, both in terms of how racist attitudes are created and how they can be overcome?

In the South African apartheid, a racially motivated system of government affected the life of all citizens. Blacks were seen as inferior and whites as superior; there were severe penalties to be paid by anyone who disagreed with this –- we all know this through South Africa’s most famous prisoner, Nelson Mandela. Segregation was entrenched in the places people lived, in the schools they attended, the beaches and parks they could visit and so on. White children raised in such a atmosphere cannot help but hold racist attitudes of white superiority and black marginalization.

After apartheid ended, the Truth and Reconciliation Commission helped acknowledge the trauma of apartheid for many black survivors and their families. It is a reconciliation that has not occurred in this country after the trauma of slavery and the Native American genocide.

Studies have shown that many people have subtle, or implicit, racial biases that they're completely unaware of. Are racial biases often unconscious? How do these unconscious biases over time develop into hateful beliefs and actions?

Implicit biases are when you're not aware that you have a race bias. You behave in a discriminatory way without realizing that you have racist values. That occurs a lot in the medical profession, for example -- physicians don't realize that they're treating some patients differently to others based on race and often based on class as well.

Again, you develop attitudes and stereotypes from socialization. Here's a common example: An older woman is walking down the road and she sees a black man approaching. She holds her purse tighter thinking that it's going to be snatched. Research has found that both black and white people often behave in this way because of our socialization. It's because of what the media says about young black men being thieves and robbers and bag-snatchers. We all tend to behave in that way based on the socialization.

Do hate crimes like the Charleston shooting tend to beget more hate crimes?

Sometimes, yes. Now there are more churches that have been burned. When there's a hate crime like this... sometimes it can escalate issues because people retreat into their separate camps. People who are racist become more racist, because something they believe in is threatened.

On the other hand, incidents like this can actually bring about positive change. Removing the Confederate flag is a positive development. I would assume that as more positive outcomes develop, people will need to hold on to their racist values more strongly, and will become even more protective of their belief systems.

You see this in the Muslim world -- as the U.S. became stronger about trying to put down al Qaeda, the Muslim world became stronger about fighting to hold onto their values.

What psychological toll does racism take on both its victims?

People get depressed and they get afraid, fearful and anxious. It can come up physically with high blood pressure and heart disease. There are big studies being done on how even sleep is affected by racial inequality, because racism keeps victimized people from being able to settle down. They are always hypervigilant because someone or something in the environment is going to threaten them based on their race. They are fearful all the time.

What is the relationship between poverty and racial inequality?

In some ways very complex but also so simple -– poverty and race go hand in hand in the U.S. In a nutshell, as there have always been strong associations between race and privilege, there are also just as strong associations between race and disadvantage, which can spiral downwards into poverty. Systemic discrimination continues to thrive in the U.S.

Examples can be taken from looking at how home loans are given -– how race may factor into this process. We all know that owning property is an important step in upward mobility, but for people of color this step is often not easy because of racial discrimination. We also see this in employment: Employers are more likely to hire a white applicant as opposed to a qualified black applicant.

What needs to happen for our society to overcome racism?

We need to have more discussions. Rather than people retreating into their separate camps, there has to be more engagement and people need to talk to each other. In Charleston, you do see black and white people coming together. That's been uplifting to see. There are a lot of white people supporting the black community. They were in church, they gave eulogies and so on. Those are positive developments. It's not something that would have happened 20 years ago, and it goes to show that we are moving in the right direction as a society -- although sometimes when these things happen, we feel like we're moving backwards.

It can be two steps forward and one back. The movement toward a pluralistic society is taking a long time and it's far overdue.

This interview has been edited for length and clarity.