Blame Your Genes!
A new study by Joshua New of Barnard College, Columbia University and Tamsin German of University of California Santa Barbara suggests that "spiders have posed such specific and immediate threats" to our evolutionary ancestors that our visual system has developed a mechanism to rapidly identify images of spiders.
In the study, to be published in the journal Evolution and Human Behavior, New showed images of spiders and other modern threats like hypodermic needles, as well as other animals like houseflies to 252 people. Most spotted the spiders much more rapidly.
"This demonstrates that some evolutionary-relevant threats are highly-specified and can evoke what is perhaps best termed 'reflexibe awareness': an immediate and elaborated perception sufficient to guide an adaptive behavioral response," New added.
"Humans were at perennial, unpredictable and significant risk of encountering highly venomous spiders in their ancestral environments," New said to The Sunday Times, "“Even when not fatal, a black widow spider bite in the ancestral world could leave one incapacitated for days or even weeks, terribly exposed to dangers. Detection, therefore, is the critical arbiter of success in such encounters — any improvements to the sensitivity, vigilance, reliability and speed of faculties for their detection would have been of significant selective advantage."
So the next time a spider give you the ooies, you can blame your genes.