More anecdata... I was never afraid of snakes as a child (much to the dismay of my mother) nor am I now, but the times I've heard the rattle of a rattlesnake ca

More anecdata... I was never afraid of snakes as a child (much to the dismay of my mother) nor am I now, but the times I've heard the rattle of a rattlesnake caused me to react in a way that was undeniably involuntary. Seemed pretty primal.