Are you afraid? So what do you believe?

The day after the 9/11 terrorist attacks, Harvard University psychologist Dan Wegner found himself dashing from store to store desperately trying to buy an American flag.

Then he realized with a start that what he was doing could be predicted by a new field of psychology that until then had been considered fringe science. His patriotic urge, Wegner recognized, was an attempt to counterbalance the scary thought of his own mortality brought on by the attacks.

The developing field, called experimental existential psychology, or XXP, explores the ways people find meaning and purpose in their lives. A topic that was once the province of poets and philosophers can be examined under the cold light of science, researchers say.

How people deal with existential concerns could help explain a broad spectrum of behavior, the researchers believe, including political and religious leanings, altruism, the pursuit of riches, patriotism and terrorism.

Already, experiments have shown that when people are reminded of their own death, they become more patriotic, more conservative, more family oriented, more security minded.

The fear of death also provokes a need to feel connected to others, to have a clear sense of identity, to know how one fits into the world, and to feel one has free will.

Wegner said his experience in 2001 convinced him this line of thinking had merit.

“I never had that need for a flag before. It just suddenly came up,” he said. “The response to the threat of terror gives you this feeling that you have to find value in your life. You have to find what it is that makes you worthwhile, and one of them is being a patriotic American.”

Psychologists have long avoided studying how people find meaning in life, believing the subject could not be pinned down by experimental evidence. From around 1920 to the 1970s, they exclusively studied behavior, something they could observe and compile data on, and most still do.

In the mid-1980s, three psychologists founded the field of XXP. They were inspired by “The Denial of Death,” a 1973 book by cultural anthropologist Ernest Becker, who maintained that the unique human awareness of death, and its denial, motivated a lot of human behavior.

The book led the trio -- Jeff Greenberg of the University of Arizona, Tom Pyszczynski of the University of Colorado at Colorado Springs and Sheldon Solomon of Skidmore College in New York -- to develop a terror-management theory to explain how people deal with thoughts of their own demise.

“The basic idea that we’re exploring is that people’s concerns about their mortality underlie a lot of their strivings to sustain their sense of meaning, to defend their belief systems and to strive for self-worth,” Greenberg said.

These thoughts are the result of a tug of war between a primitive instinct to survive at all costs and a brain that is not only conscious of its own existence but also is aware that in the long run survival is a losing battle.

What am I doing here? Am I alone in the universe? Is life meaningless? How will I be remembered? Did I do the right thing?

With other animals, said Northwestern University psychologist Dan McAdams, “it’s not like they’ve got any kind of understanding that they’re going to die. They react to the world in a way to survive, but they don’t go to sleep at night thinking, ‘Oh my God, how many years do I have left?’ ”

The three psychologists set out to devise experiments to examine these kinds of thoughts -- an effort that a recent psychology journal described as “Introducing Science to the Psychology of the Soul.”

In one such study, when students were asked if they supported using nuclear weapons against terrorists, the majority of both liberals and conservatives said no. But among students reminded of death, a majority of conservatives were in favor of using nuclear weapons. The majority of liberals still were against it.

Similar results were found in a study Greenberg conducted with an Iranian colleague. The majority of Iranian students favored peaceful approaches over suicide bombings as a strategy for dealing with international problems. But when their mortality became an issue, the results were the opposite.

Study subjects are reminded of mortality in various ways, including being asked to think about it, being walked past a funeral parlor and being shown a computer screen with the word “dead” flashed too fast to be consciously registered.

“What makes Greenberg and his colleagues special is that they’re hellbent on bringing this stuff into the lab in a very hard-nosed experimental quantitative sense,” McAdams said. “That’s what distinguishes them from a lot of other people who study meaning from a scientific standpoint.”

The traumatic 9/11 attacks were the turning point for the field. The American Psychological Assn. asked Greenberg, Solomon and Pyszczynski to write up their research in a book that might help explain why some people engage in terrorism and how others respond.

Among the points made in their 2003 book, “In the Wake of 9/11: The Psychology of Terror,” was that modern people are much more exposed to “alternative meaning systems” than in the past.

“We have different versions of God, different versions of evil,” Greenberg said. “It’s one of the things that contributes to some of the large-scale conflicts that exist in the world. With exposure to other people and other belief systems, there’s a threat to our own sense of meaning.”

Some of the things Americans do, for example, violate the belief system common among residents of the Middle East, and vice versa. People in the Middle East tend to be less materialistic and more spiritual, Greenberg said. They think about death more consciously, and they consider people who die for their beliefs to be martyrs.

“And because we don’t understand their worldview, we’re angering them in a very deep way and we don’t understand it sometimes,” he said. “Our hope is that by understanding psychologically where people are coming from ... we can use education, communication and other diplomatic tools to try and change the way we’re viewed.”

In the United States, the threat of terrorism has made citizens feel more vulnerable and more anxious for security. A study Greenberg and his colleagues conducted before the 2004 presidential election found that college students were slightly in favor of Democrat John Kerry. But when the students were reminded of their mortality, a fear that terrorism provokes, the majority favored his Republican opponent, George W. Bush.

“It’s the psychology of the soul in the sense of looking at the deepest things we rely on in our lives,” he said. “It is a sense of inner being that helps us function and feel secure in what’s really a scary world.”

This idea also may help explain why some people living in an impoverished city neighborhood turn violent if they perceive their self-worth being disrespected or “dissed,” Greenberg said.

Pelin Kesebir, a graduate student in social psychology at the University of Illinois at Urbana-Champaign, is conducting research in existential psychology. She found that when students were reminded of their mortality, they thought more about the meaning of life and they needed to think that the things they believed in are long-lasting.

They assert, for example, that people who represent American values (Kesebir named Oprah Winfrey as an example) will be remembered for a very long time -- twice as long as the time given by students not thinking about death.

“Famous people serve as an existential buffer,” she said. “Their imperishability mollifies people’s existential anxieties.”

“We all want a sense of continuance, a sense that we’re more than just these temporary creatures on this dirt ball,” Greenberg said. “We want to feel we’re significant beings in a meaningful world.”