In a world that includes brutal wars, mindless killing, terrorism, and even genocide, it is not uncommon to lament the violent state of the human condition. However, Steven Pinker, an experimental psychologist at Harvard University, argues that people are actually living with much less violence today than in the past. In The Better Angels of Our Nature: Why Violence Has Declined, Pinker explores human violence across the centuries, drawing on historical and scientific data, as well as popular culture, war studies, and game theory. He recently spoke with U.S. News about the reasons he says are behind the decline in violence, the high rate of crime in the United States, and whether there is hope for a more peaceful future. Excerpts:

What spurred you to write this book?

We know from the historical record that violence can change over time. It was realizing that many different kinds of violence had come down over many different scales of time that prompted me to devote an entire book to that phenomenon.

Where does violence come from?

There are motives in the human brain that can tempt us towards violence and there also are motives that inhibit us from violence. In one chapter of the book called "Inner Demons," I lay out five different kinds of violent motives including pure predation or exploitation, drive for dominance, revenge, and sadism. I also have a chapter called "Better Angels," and it discusses the parts of human nature that pull us away from violence such as empathy, self-control, a sense of fairness, reason, and rationality. Whether violence erupts depends on which of those human capacities has the upper hand.

Why has violence persisted?

The parts of the human mind that tempt us towards violence have not gone away.

What are the causes of the decline of violence over time?

Effective governance is one. The spread of trade and commerce has brought violence down, when it becomes cheaper to buy something than to steal it and more and more of the world becomes more valuable alive than dead. The spread of education, literacy, and rationality have led people to think of violence as a problem to be solved rather than as a contest to be won. The expansion of people's experiences through reading fiction, through consuming history and the media, have expanded people's circle of empathy. [Read more Book Club interviews by subscribing to U.S. News Weekly, now available on the iPad.]

Is there scientific evidence that says people have become more reasonable over time?

Yes, there's a phenomenon called the Flynn Effect, by which IQ scores have risen by 3 points a decade throughout the 20th century in every country in which it has been measured.

Are there some kinds of violence that are gone for good?

I don't think we are going to reintroduce human sacrifice, throwing a virgin into a volcano to improve the weather. Or institutionalize slavery, or burning heretics at the stake. I also don't think homicide is going to go back to the level that it was at during the Middle Ages, where it was 35 times more common than it is today. I don't think Western democracies are going to go to war with each other again.

Will other types of violence continue to disappear in the future?

It is hard to predict. Crime rates go up and down within a certain range without anyone being able to predict exactly why or when. It just takes one kook or one small group of fanatics in a world of 7 billion people. Even if there is a massive trend away from violence, it's always possible that there will be a small terrorist cell or, for that matter, a lone sniper like the Norwegian. So violence committed by a small number of individuals is unlikely to go away.

How does the United States compare to other democracies in the Western world?

The United States has a higher rate of violence, partly because large parts of the country were in a state of anarchy until the 20th century. People could not count on the government to protect them. The cliché of the cowboy movies is that the nearest sheriff is 200 miles away, so you have to protect yourself with your six-shooter. When governments did arrive, people were reluctant to hand over their self-protection. And because the first government in America was a democracy, people were able to impose their wishes. In European countries, first the government disarmed the people and exerted its control many hundred years ago. Then the people democratized the government, but by then the government had already established control.

Who should read this book?

Everyone. Who isn't interested in violence? We all watch crime dramas, murder mysteries, and Shakespearean tragedies. Why not convert that interest in violence into an understanding of why violence occurs and how it can be minimized?

See pictures of the crackdown in Syria