DAVID GREENE, HOST:
An event like the Boston Marathon attack is partly physical - intensely so. Almost all of us have seen the images from near the finish line on Monday. But a huge part of this event is also the effect it has on our minds. Psychologists have spent years analyzing conscious and unconscious reactions to tragedies, including 9/11.
STEVE INSKEEP, HOST:
Some of them spoke with NPR's Alix Spiegel.
ALIX SPIEGEL, BYLINE: We've seen it on the news.
(SOUNDBITE OF BOMB EXPLODING)
SPIEGEL: There's the sound of a bomb exploding - smoke and chaos and people running in every direction, a short glimpse of a man on the ground gripping his leg - and then the second blast.
(SOUNDBITE OF BOMB EXPLODING AND SCREAMING)
SPIEGEL: From the first explosion to the last is 15 seconds. And in those 15 seconds, three people dead, including an eight-year-old boy and more than a hundred wounded. And for those of us watching, a profound reminder of a reality we would prefer to ignore.
JEFF GREENBERG: When these things happen, it reminds you of the fragility of life, right, and that death is something that can happen very suddenly, very unexpectedly. If terrorists don't get us, something else might and eventually will.
SPIEGEL: This is Jeff Greenberg, a psychologist at the University of Arizona who studies how people consciously and unconsciously respond to events that force them to confront their own mortality and vulnerability - events like Boston. The idea of our own death, Greenberg says, is incredibly challenging and often our response follows a kind of predictable, psychological script. There's the horror we feel as we watch the event unfold but with it a quiet assessment. How vulnerable are we?
GREENBERG: And generally in sort of a biased way to try and deny your vulnerability.
SPIEGEL: Greenberg says studies have shown that most of us find ways to discount the possibility that the thing on the screen could happen to us - big and small reasons why we in particular are safe. Greenberg says he even sees this in himself. On Monday after the bombing, he found his mind making a calculation.
GREENBERG: You know, I'm here in Tucson, I'm like, you know, this is the last place anybody's going to bother hitting. You know, it's not me and it's not now.
SPIEGEL: And, Greenberg says, in the early stages of an event like this, we and our leaders also do what we can to kind of reassert our sense of control. We make plans for what to do if something bad hits our city, we increase our vigilance. But what's really interesting is how events like this affect us after they've left the front page and our conscious minds.
GREENBERG: The thoughts of our mortality seem to linger outside of our conscious attention but still affect us.
SPIEGEL: Greenberg and his colleagues know this because for months after 9/11, they gave people incomplete word stems and asked them to finish the words.
GREENBERG: You could fill it out with a death-related word or a non-death-related word. So, for example, C-O-F-F blank blank could be either coffee or coffin.
SPIEGEL: For a long time after 9/11, the probability that people would choose coffin instead of coffee was higher than normal. And, Greenberg says, when the specter of our own death is there under the surface, we see the world very differently than when it's not.
GREENBERG: When death is percolating close to consciousness, people become more us versus them. They become more defensive of their belief systems, positive toward those they identify with and more negative to those who espouse a different belief system.
SPIEGEL: Dozens of studies have shown this, and Greenberg believes that this tendency, to embrace our own belief system more strongly in the face of death, is part of the reason the country got more polarized after 9/11.
GREENBERG: At first everybody got closer together. It lasted a few months. And then after that America became more polarized than ever and people became more invested in their own belief systems, whether it be conservative or liberal.
SPIEGEL: Now, obviously, when it comes to Boston, it's still early. Not close to clear who is responsible for what happened. Still, Greenberg says, Boston is a reminder: death is coming. There's no way around it. Alix Spiegel, NPR News, Washington.