If you look at contemporary psychological theories of aggression, it becomes clear in a hurry that numerous antecedent conditions can bring about an aggressive response. In Iraq, we may very well be witness to a confluence of conditions that are responsible for the current level of violence as well as predict an escalation in the coming months. Let's examine a couple of those factors:

1. Uncomfortable heat:

There is now ample evidence that uncomfortably hot temperatures are causally associated with increases in aggressive behavior. In laboratory studies, individuals who are placed in uncomfortably hot conditions tend to deliver higher levels of shock or noxious white noise to their presumed victim than do individuals placed in relatively comfortable room-temperature environments. Lab data also shows a causal link between uncomfortably hot temperatures and increases in level of anger. Research on archival data, such as police and FBI records, shows that violent crimes, such as homicides and aggravated assaults, tend to show an increase during the summer months, and also tend to spike late in the afternoon or into the evening following hot days.

Think about the time of year. Spring is an apparently short season in Iraq, and the summers are unbearably hot with high temperatures regularly exceeding 110 degrees Fahrenheit in many locations. There is also no plausible way for many Iraqis to escape the heat: electricity is still pretty undependable, and for the average Iraqi may be unaffordable. For that reason alone, I might expect to see an increase in unrest.

2. Frustration:

The earliest model of aggression was proposed by Dollard and several other colleagues at Yale University during the 1930s: that is, the frustration-aggression hypothesis. The main thrust of the hypothetical model is that frustration (i.e., blocking an individual from attaining a goal) can lead to an aggressive response. One early application of Dollard and colleagues' frustration-aggression hypothesis was aimed at examining the role of economic hard times on such behaviors as homicides and various other violent activities, which from their archival research there seemed to be some support for their hypothesis. Frustration is associated with increases in various physiological measures such as heart rate, as well as anger, as well as aggressive behavior; indeed there is tons of laboratory evidence to support the hypothesis, as well as quite a number of creatively executed field experiments.

Think of what the average Iraqi may be facing on a day-to-day basis. Efforts at finding meaningful work may be frustrated for any of a number of reasons, which means that efforts to provide for one's self and family are frustrated. The expectation of a regular flow of electricity during the summer months may also be frustrated. Efforts to move freely to conduct one's business may be frustrated to varying degrees as the occupation continues.

3. Provocation:

Sometimes frustration is described by aggression theorists and researchers as one form of a broader category: provocation. Whether frustration really fits there is certainly subject to debate. When I discuss provocation to my students, I define the term as an action intended to elicit a strong response from the target of the provoking behavior. Most provocations fall under two categories: physical assaults and verbal attacks. Again, there is a ton of laboratory evidence and field research that demonstrates conclusively that there is a causal link between provocation and aggression. One thing to mention is that sometimes behaviors are unwittingly provoking - perception then becomes an important part of the equation.

Again think about what's going on to the average Iraqi. The various news reports surely suggest behaviors by coalition troops as well as various mercenaries that would fit the definition of provocation. Other acts may end up seeming provoking simply because to provocateur failed to understand the cultural norms governing acceptable behavior among the natives. Again, perception is of critical importance.

It is likely that what we are now seeing is a particularly volatile combination of these three factors (and probably others). For those of us who are pessimistic about the near future of Iraq under occupation, basic social science research on aggressive and violent behavior is unlikely to give us any cause for changing our tune. For the optimists, perhaps they would do well to reconsider their optimism in light of available theory and data.