Lieutenant Colonel Dave Grossman is an author who has specialized in the study of the psychology of killing, which has been termed 'killology'.
Col. Grossman retired from the military as Professor of Military Science at Arkansas State University. His career includes service in the US Army as a sergeant in the US 82nd Airborne Division, a platoon leader in the 9th Division, a general staff officer, a company commander in the 7th (Light) Infantry Division as well as a parachute infantryman, a US Army Ranger and a teacher of psychology at West Point.
Col. Grossman's first book, On Killing: The Psychological Cost of Learning to Kill in War and Society is an analysis of the physiological processes involved with killing another human being. In it, he reveals evidence that most people have a phobic-level response to violence, and that soldiers need to be specifically trained to kill. In addition, he details the physical effects that violent stresses produce on humans, ranging from tunnel vision, changes in sonic perception, and post-traumatic stress disorder.