Watch out for cars with bumper stickers.
That’s the surprising conclusion of a recent study by Colorado State University
social psychologist William Szlemko. Drivers of cars with bumper
stickers, window decals, personalized license plates and other
"territorial markers" not only get mad when someone cuts in their lane
or is slow to respond to a changed traffic light, but they are far more
likely than those who do not personalize their cars to use their
vehicles to express rage — by honking, tailgating and other aggressive
It does not seem to matter whether the messages on the stickers are
about peace and love — "Visualize World Peace," "My Kid Is an Honor
Student" — or angry and in your face — "Don’t Mess With Texas," "My
Kid Beat Up Your Honor Student."
…Drivers who do not personalize their cars get angry, too, Szlemko and
his colleagues concluded in a paper they recently published in the
Journal of Applied Social Psychology, but they don’t act out their
anger. They fume, mentally call the other driver a jerk, and move on.
"The more markers a car has, the more aggressively the person tends
to drive when provoked," Szlemko said. "Just the presence of territory
markers predicts the tendency to be an aggressive driver."
Here is much more, with some interesting theory in the article as well. Apparently bumper stickers indicate that the driver has a particular, and potentially dangerous, sense of territoriality.