Science & Technology

These Are the World's Scariest Animals, Ranked by Science

Some people are afraid of rollercoasters and others are afraid of heights, but when it comes to creepy-crawlies, most of us have something in common. Whether it's snakes, spiders, or cockroaches, they have a distinctive knack for sending chills down our spines and making our hearts race. Animal-based phobias are so common that there are entire movies made about them ("Arachnophobia," anyone?) But why are these reactions so universal, and what exactly causes them? A recent study set out to answer that question.

Phobia of the Fittest

Why are so many people afraid of spiders and snakes? Evolution might have the answer. According to Martin Seligman's theory of biological preparedness, animals that learn to fear harmful things faster are more likely to survive, which could explain why research shows that even babies are afraid of spiders and snakes before they've had much experience with them.

But there's another piece of the animal-phobia puzzle: disgust. Take cockroaches, for example: They're unlikely to attack humans, but many people are still horrified by them. That feeling comes not from outright fear, but from disgust. While fear is a reaction that keeps you protected from physical injury, disgust is there to keep you protected from disease and contamination.

But up until now, scientists were unclear on whether fear and disgust were two separate dimensions of animal phobias, or were interrelated feelings that could be triggered in the same person by the same animal. To figure that out, a recent study published in the British Journal of Psychology dug into people's animal phobias.

A Dictionary of Fear From Ant to Wasp

To start, researchers from the National Institute of Mental Health and Charles University in the Czech Republic pored through animal phobia studies and phobia encyclopedias to find a rough approximation of the most prevalent animal phobias out there. They came up with a list of 24 animals, which included (in alphabetical order): ant, bat, bull, cat, cockroach, dog, fish, frog, horse, lizard, louse, maggot, moth, mouse, pigeon, rat, rooster, roundworm, snail, snake (both a venomous viper and a non-venomous grass snake), spider, tapeworm, and wasp.

Next, they showed pictures of their fearsome beasts — plus an adorable red panda as the control — to more than 2,000 online participants and had them rate their fear and disgust reactions to each photo, in addition to completing a battery of fear and phobia surveys.

Once they had collected their data, the researchers were able to group the animals into five categories based on their overall fear and disgust ratings: fear-relevant, non-slimy invertebrates like ants and cockroaches; mouse-like animals like rats and bats; snakes and lizards; human endo-and exoparasites, like lice and maggots; and farm and pet animals like cats, dogs, and horses.

Eight Legs Always Wins

The results, while not surprising, were enlightening. Snakes and non-slimy invertebrates triggered the most fear while farm and pet animals were the least gross and scary. The animals most often rated with the highest possible fear score were spiders and venomous snakes, while the ones most often rated with the highest possible disgust score were (again) spiders, tapeworms, roundworms, lice, and maggots.

It's no surprise that spiders ranked highest on both fear and disgust. Despite the fact that they're tiny and relatively harmless, the researchers think their quirky "'too-many-legs' body plan" and the fact that we never know where we'll encounter one next account for their popularity as a fearsome pest. The venomous snake came in right behind the spider as the most feared animal, supporting the idea that we're somehow wired to fear snakes and spiders above all other animals. However, the same wasn't true of the non-venomous grass snake, which shows that humans (at least those without a snake phobia) are capable of adjusting how afraid they are based on the particular threat level.

"To our knowledge," the researchers write, "this is the first study to show that snake fear much depends on the specific species presented to the subject which should be reflected in future research."

Surprisingly, this study showed that rats, mice, and lizards didn't elicit fear at all from the participants. Maybe "Ratatouille" successfully rebranded the rodent?

This study's results also align with other studies that show women report higher fear and disgust levels than men. The researchers think this might have to do with "higher reproductive cost," or the idea that women need to worry not only about their own health but also about the health of their children. Women being more fearful of dangerous animals and parasites might give the human species an evolutionary advantage.

But regardless of gender, this study shows that the fear and disgust that some animals bring out in us aren't necessarily weaknesses on our parts. It seems to be a complex, intertwined reaction that's been keeping us healthy and unharmed for generations.

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For a whimsical look at the most popular fears, check out "The Pop-Up Book of Phobias" by Gary Greenberg. We handpick reading recommendations we think you may like. If you choose to make a purchase, Curiosity will get a share of the sale.

Written by Julia Wilde July 19, 2019

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