http://articles.mercola.com/sites/articles/archive/2005/12/20/what-makes-us-laugh-why-dont-you-laugh-when-you-tickle-yourself.aspxBy Paul J. Rosch, M.D. President, The American Institute of Stress Clinical Professor of Medicine and Psychiatry New York Medical College Originally published in Health and Stress, the newsletter (November 2005) of The American Institute of Stress WeenCommunityServer 2008.5 SP1 (Build: 31106.3070)