It is commonly known that humans are afraid of the unknowns. If science would reveal more infos of these unknowns. Human would have been less afraid of these ghosts.
Checkout the questionaires.
http://cgi.ebay.co.uk/Pre-owned-APACHE-AH64-A-D-Longbow-American-Spec_W0QQitemZ4623857135QQcategoryZ32635QQssPageNameZWDVWQQrdZ1QQcmdZViewItem