Psychology professor Lt. Col. Dave Grossman talks about his new book "On Killing: The Psychological Cost of Learning to Kill in War and Society". He maintains that it is inherent in us to resist killing our own species and that research has proven that many soldiers engaged in face-to-face combat found it difficult to kill. Soldiers can be trained however, to overcome that resistance. Some veterans are still plagued with guilt about taking another man's life, but this guilt can be eased if they are assured that what they did was right. Addressing the rise in civilian murders, he believes that part of the reason is that children are becoming desensitized to violence because they are associating the bombardment of graphic images by the media with pleasure. (Originally aired March 1996).