"People don't change their behavior dramatically when they get in the car," Kathleen Harder, co-author of the study, told the St. Paul (Minn.) Pioneer Press.

She and two others administered a battery of personality, emotional and behavioral questions to a group of 710 drivers between the ages of 18 and 45.

They discovered that a group who scored as "high hostile" in the survey became "more emotionally activated while driving" than people labeled as "low hostile," Harder said.

As a group, the high-hostiles reported driving after drinking more often than the low-hostiles, taking more risks while driving and becoming angrier at slow drivers, police, discourteous drivers and road construction, she said.