Six years after 9/11, all too many Americans still have only a vague idea of what does — and doesn’t — motivate terrorists. It doesn’t help that many politicians exploit the anxiety that terrorism evokes to promote their own agendas. Here are five key urban legends:

1. Terrorism is a random act carried out by irrational people who hate our way of life.

If only it were that simple. In fact, terrorists are typically motivated by geopolitical grievances, not blind hatred. The agendas of individual terrorist groups vary, but their tactical goal is always more or less the same: to sow fear and confusion by deliberately targeting civilians in order to intimidate a country into changing its policies and ways.

So political calculations are key here. Citizens of countries that occupy other countries, for example, are more likely to be targeted by terrorists. In addition, wealthy democracies are more likely to be the targets of terrorist strikes than are totalitarian regimes, which suggests that terrorists deliberately strike countries that are susceptible to public pressure.

Another reason not to see terrorist attacks as random: They’re often timed to occur when they can have maximum impact, such as the eve of pivotal elections. In Israel, for example, attacks by Palestinian terrorist groups bent on sabotaging peace talks are more frequent before elections when left-wing governments hold power, in hopes of pushing Israeli voters in a more hawkish direction, according to research by Claude Berrebi of the Rand Corporation and Esteban F. Klor of the Hebrew University of Jerusalem.

There’s even a cold logic to the time of day that terrorists pick for their attacks, which also suggests a rhythm that’s far from random. My analysis of U.S. government data from the National Counterterrorism Center reveals that terrorists are most likely to strike in the morning — in time to enter the day’s news cycle.

2. Terrorists are no different than ordinary criminals.

Wrong. Criminals tend to be poor and uneducated. But terrorists tend to come from families with above-average means and are often well-educated. For example, Jitka Maleckova of the Russell Sage Foundation and I found that members of the military wing of the radical Shiite group Hezbollah who were killed in action in the 1980s and early 1990s were better educated and less likely to be poor than their Lebanese countrymen. Other researchers have found similar results for other terrorist groups. People who join terrorist organizations often have legitimate, well-paying jobs, unlike common criminals.