ORLANDO – One of the most common popular misunderstandings about the causes of terrorism is the notion that terrorists must be "insane” to behave as they do. That idea is as wrong as it is comforting.

Conservatives in the United States, for example, frequently rail against the "madness” of Islamic terrorists, and regard attempts to understand terrorism as appeasement or liberalism gone wild. In the wake of September 11, 2001, in particular, many on the right mistook the attempt to understand or explain the terrorists’ actions as an effort to condone them.

We have been here before, though. After World War II, the myth of the "mad Nazi” exerted a forceful grip upon the popular imagination; surely, only insane individuals could perpetrate something like the Holocaust. But social science research in the 1940’s and 1950’s, including interviews with surviving Nazi leaders, demonstrated that members of the German governmental hierarchy were not only sane, but also highly intelligent.

Moreover, by the early 1960’s, the social psychologist Stanley Milgram had shown that ordinary Americans would go to extraordinary lengths in obeying malevolent authority. He famously induced people from a variety of social classes and occupations to administer what they thought were increasingly harsh electrical shocks to a helpless victim (played by an actor) sitting in an adjoining room, and his findings have since been replicated around the world.

This was an unpalatable conclusion. Faced with the horror of what the Nazis had done, most people found it psychologically easier to think of what had happened as the behavior of mentally unhinged individuals, or the result of some sort of collective fugue. But had vast numbers of Germans suddenly lost their senses overnight, or were they part of a situation in which most of us would simply have done as we were told?

A similar resistance to noisome conclusions – and similarly understandable from a psychological viewpoint – informs today’s thinking about terrorists. Our default reaction, often reinforced by Western philosophical traditions and simplistic political rhetoric, is that evil acts must be the product of fundamentally evil or insane individuals.

As with the Nazis, the study of modern terrorism began from the starting position that a single disposition – known in the literature as the "terrorist personality” – characterizes most or all terrorists. In the 1970’s and 1980’s, West German authorities allowed psychologists and psychiatrists to interview terrorism suspects then being held in prison or awaiting trial, including members of the Red Army Faction.

A brigade of experts descended on the jails, looking for evidence to justify their own pet theories of terrorist psychology. Terrorists were all self-serving narcissists, some found after the interviews were done. Others argued that terrorists were all victims of clinical paranoia or some other psychosis. Some even suggested, somewhat bizarrely, that terrorists tend to have lost a parent in their childhood years and are acting out the aggression that derives from their resulting frustration with life.

All of these views shared the belief that there was something fundamentally dysfunctional about the "terrorist personality,” something warped and unusual that sets "them” apart from "us.” Never mind that different researchers found different features of this so-called personality salient, and came to fundamentally different conclusions about it.

In the years since, social science has reinforced skepticism that all terrorists share such essential personality traits. There is also a growing recognition that the social circumstances to which terrorists are exposed play a significant role.

What we know about the mindset of terrorists tells us that they are mostly not deranged or insane, but have acquired a different set of beliefs and been exposed to social conditions very different from our own. Put simply, the causes of terror are largely situational, and the situations are themselves as varied as the acts themselves (members of the IRA, for instance, have obviously been exposed to circumstances very different from members of Al Qaeda).

It must be admitted, of course, that our access to real-life terrorists is limited, and we still have much to learn about the kind of environments that foster terroristic behavior. Arguably, our knowledge of the factors that led to the July 2005 bombings in London, for example, is still far less impressive than our ignorance.

The great contribution of social science to the understanding of human evil has been to expose unpalatable truths. When we resort to psychologically comforting but misleading assumptions about terrorism, we hamper our own understanding of political violence in general – and hence weaken our ability to avert or minimize it.

David Patrick Houghton is a professor of political science at the University of Central Florida.

Copyright: Project Syndicate, 2011.