To remind my sister that we had tickets for Elvis Costello at the Van Duzer Theater, I grabbed a photo of Elvis off the web, stuck a word balloon next to his face and inside typed the words "Don't forget tomorrow night!" Then I took a picture of that with my phone and messaged it to her.

We live in the age of the visual image. That means we live in dangerous times.

A video last year of a young man setting himself on fire in Tunisia sparked riots that brought down three Arab dictators. A 14-minute YouTube video last month that mocked the Prophet Muhammad sparked riots in the Arab world that lead to the death of U.S. Ambassador Chris Stevens in Libya and at least 14 people in Pakistan.

Newspaper articles don't cause riots. Articles and essays get us to think, not act. Books don't have that effect either. Back in 1988, the Ayatollah Khomeini put out a $1 million reward for anyone who would kill author Salman Rushdie as punishment for his book The Satanic Verses, which he said insulted the Prophet Muhammad. Riots broke out in the Muslim world as a result. But the book didn't spark the riots.

The book had been out for months. It was the Ayotollah's announcements, along with news that India banned the book, that sparked the riots. None of the people who rioted read the book.

Recent research shows that what we hear produces visual images in our brains, and we react impulsively and emotionally to these mental pictures.

In an article published in the magazine Psychological Science in June, Harvard psychologists Elinor Amrit and Joshua Green found that visual images heighten our emotional responses. And they found that when a visual image --or an image we visualize in response to something we hear --forces us to make a choice, we will veer toward what is most important to us as individuals rather than the greater good. In other words, if we see something that forces us to choose between a strong personal belief, like religion, and a more philosophical or reason-based belief that benefits the larger community-- such as public safety or due process or free speech -- people will sacrifice the philosophical concepts and the common good to protect their individual integrity.

Pictures stir our passions. And passions spur actions that reason won't stop. Oliver Wendell Holmes, one of the fathers of American legal theory, once said: "I cannot argue a man into a desire. But although desire cannot be imparted by argument, it can be by contagion. Feeling begets feeling, and great feeling begets great feeling. ... As life is action and passion, it is required of a man that he should share the passion and action of his time."

So something we hear or see can get us to act as a mindless mob. Nazi mastermind Joseph Goebbels understood this. The Nazi party emerged just as radio and movies and photographic images became dominant media forms. He realized that if you could control these images -- make it is so that people saw only those images you wanted them to see -- you could stoke their passions and fears and incite them to act. In my history classes I ask my students this: How do you take a country of rational people and get them to commit mass murder on innocent civilians? That's what happened in Germany during World War II.

If you think that kind of crazy stuff can't happen here, remember, we've had riots. Images of four police officers acquitted of beating up Rodney King sparked massive riots in Los Angeles in 1992. Images heighten our emotions. Passion spreads like a contagion.

So how do you tamp down passions in the age of mass imagery? Should we try to censor the images people see and the things people hear over the digital airwaves? Should we figure out how to make sure some idiot can't post an inflammatory video of the Prophet Muhammad? Should we arrest someone for painting a swastika on his garage door? Should we fine companies or organizations that distribute these images?

President Obama says no.

In a speech Sept. 25 to the United Nations General Assembly he said of the Muhammad video: "I know there are some who ask why we don't just ban such a video. ... Americans have fought and died around the globe to protect the right of all people to express their views -- even views that we disagree with. We do so not because we support hateful speech, but because our Founders understood that without such protections, the capacity of each individual to express their own views, and practice their own faith, may be threatened. We do so because in a diverse society, efforts to restrict speech can become a tool to silence critics or oppress minorities. We do so because ... the strongest weapon against hateful speech is not repression, it is more speech. ... I know that not all countries in this body share this understanding of the protection of free speech. Yet in 2012, at a time when anyone with a cell phone can spread offensive views around the world with the click of a button, the notion that we can control the flow of information is obsolete. The question, then, is how we respond. And on this we must agree: There is no speech that justifies mindless violence."

But if we can't control the flow of information from computer to computer and phone to phone, how can we prevent the violence that images incite?

Part of me thinks we are doomed.

Still, I go back to what Obama said about combating bad imagery with competing images. Remember the Nazis needed to control media to get people to do what they wanted them to do. In places with free expression, that expression gets too messy to control. Obama says we can't control it in the age of the Internet. But I say we don't want to. If you can control messages you can manipulate passions. Uploading an inflammatory video onto the Internet is a hateful and stupid thing to do. But there seem to be endless numbers of hateful and stupid people in the world. Perhaps the more times these idiots do something like that, the more likely their actions will lose their inflammatory power. At that point, the pictures and videos will just seem idiotic.

Marcy Burstiner is an associate professor of journalism and mass communication at Humboldt State University.