Well, I don’t know of any study that’s extrapolated it out mind you… but it IS true that those who have a lot of bumper stickers, magnet decorations, plate holders, etc., on their car – really, ANY kind of customization like that – are more aggressive drivers.

The reason is basically that people treat the car they drive as a territory… the more you personalize it, the more you attach yourself to it, and therefore, the more you start to see it as an extension of yourself, and therefore, the more pissed off you get at people for trying to invade “your” space on the road, as if they are personally threatening you (rather than “threatening” the faceless machine you are riding in).

This is actual science, though I forget who did it. I was pretty impressed though.