The study was done by a doctorate student at Colorado State University.
Student William Szlemko found those who personalize their cars in some way felt more attached to their vehicles.
"When they feel someone is invading that territory they are more likely to respond with aggression to defend that territory," Szlemko said.
Szlemko hopes his findings get used in the effort to stop aggressive driving, a major cause of road accidents in the U.S.
