I have always liked Bruce K. Siddle and his PPCT organizations psychophysiological research on close combat violence so here is a excellent article by Lt. Col. Dave Grossman and Bruce Siddle on realistic violence and its effects on martial skills and psychological barriers.

Its Lt. Col. Dave Grossmans Killology research group site and there are many other excellent articles there for those who wish to read through them.

Cheers,

http://www.killology.com/art_psych_combat.htm