Why are we afraid of spiders?

Who's afraid of spiders?

About a quarter of all Americans report having a fear of spiders and insects. ¹ Now we aren't talking about phobias, just general fear.

And when I asked my bug enthusiast audience on Snapchat if they were comfortable holding a spider, 57% of them said no. In fact, even among entomologists - people who study things like cockroaches and fly larvae - there are quite a few who fear spiders.^{2 3}

So where does this fear come from?

Is a fear of spiders biological?

A prevailing hypothesis is that a fear of spiders is biological, that it is something hardwired in our brains to help protect us from danger. One study showed infants pictures of either spiders and flowers, or snakes and fish, then measured pupil dilation to measure their fight-or-flight response. Why infants? The researchers wanted to be sure any observed behavior was indeed built-in and not learned. They did find that the pictures of spiders elicited a stronger response than the pictures of flowers, and snakes more than fish. This would seemingly indicate some built-in aversion to spiders, but when you compare fish to spiders, the fish had a stronger response.⁴ Additionally, there were some issues with the claims and methods of that study, so it's in no position to make any strong conclusions.⁵

Other studies have also compared responses to both snakes and spiders. The snake detection hypothesis⁶ posits that primate evolution was in part driven by a need to avoid snakes. One study showed that snakes elicit a stronger visual response than spiders.⁷ Another interesting study involved three female Japanese monkeys who had been born and raised in captivity and thus never exposed to snakes or spiders. These monkeys were able to more quickly visually identify snakes than they could spiders.⁸ Now this study was definitely limited by only testing three monkeys, but it does point us in the direction of a fear of spiders not being baked into our biology. In fact, the authors of that paper state the following:

To our knowledge, there have been no reports of primates being afraid of spiders in the wild. Not only have there been no reports of nonhuman primates being afraid of spiders, but also several taxa perceive them as food.

It makes sense that snakes would elicit a greater response than spiders. There are about 50,000 known species of spider,⁹ and only about 100 of those are a concern medically.¹⁰ That comes out to only 0.2% of spider species worldwide. And of those 100 medically significant species, fewer than 30 have caused human deaths¹¹ - only 0.06% of spider species are capable of killing a human! On the other hand, out of the 3,500 known snake species, 600 are venomous and 200 of those are capable of killing a human.¹² That comes out to 17.1% of snake species being venomous and 5.7% that can kill a human.

Is a fear of spiders cultural?

Furthermore, being afraid of spiders is not universal; it is more prevalent amongst those of European descent.^{13 14} During the middle-ages, spiders were associated with the plague, and this association may have transformed into a spider aversion that was taught from generation to generation via social learning. It wasn't until much later that we discovered that the plague was actually spread by fleas and rats; spiders just happen to inhabit many of the same places that rats do.

Moving outside of Europe, we see in ancient China that spiders were referred to as 'happy insects' and were associated with good luck.¹⁵ The Spider Grandmother was one of the creators of the world in Hopi mythology, and for the Navajo the Spider Woman was a protector of humans.¹⁵ Now in Japanese folklore spiders would take on the role of villain,¹⁵ so spiders weren't always regarded with high esteem, but we do see that throughout human history spiders weren't universally despised. If we were born with a fear of spiders, we might expect to see this fear in all cultures, but we don't.

Conclusion

So where does that leave us? Well, being afraid of spiders is most likely not human nature. Cultural differences, historical misconceptions, social learning, and personal negative experience seem to play a bigger role than our biology. When you look at the numbers, spiders are way less dangerous than we tend to think. I don't expect you to start loving spiders or to befriend every spider you see. But next time you spot one of these eight-legged creatures, take a moment to consider where your reaction really comes from. You might find that your fear has more to do with what you've learned than any actual threat. And who knows? Maybe understanding this will help you see spiders in a slightly different light - or at least make that encounter a little less scary.