Based on some googling it sounds like the Amygdala does respond quickly to spiders and snakes, etc. but then the higher portions of the brain kick in to suppress fear or not.
Okay, I did not find the study previously mentioned and I could have imagined it for all I know. This article seems to cogently discuss what is currently known about the human response to snakes.
There does seem to be evidence that there is some kind of an innate snake response which is triggered and shaped by environmental factors.
For what it’s worth, I don’t seem to possess it myself. I used to keep snakes as a child and even now, unless they rattle I find snakes merely interesting, like any other creature.
What a great article.
The article cited by Ulfreida deserves to be named here; a check now on JSTOR shows over 100 citations of it in the scholarly literature. It certainly is on the money for everybody in this thread.
“The Malicious Serpent: Snakes as a Prototypical Stimulus for an Evolved Module of Fear”
Arne Öhman1 and Susan Mineka
Department of Clinical Neuroscience, Karolinska Institute, Stockholm, Sweden (A.Ö.), and
Department of Psychology, Northwestern University, Evanston, Illinois (S.M.)
Current Directions in Psychological Science, 2003