Animals are among the most powerful triggers of human fear. It is what makes them such great antagonists in the cinematic universe – think: Bruce in Jaws, the Graboid in Tremors, and, of course, Aragog from the Harry Potter films. 

This is not that shocking: Throughout our history, animals of all shapes and sizes have posed some kind of evolutionary threat, whether that be as vectors of disease or as vicious predators. It makes sense from a survivalist point of view. After all, that instinctive fear kick could be the difference between life and death.  

Naturally, as we transitioned from hunter-gatherers to office drones, those fear instincts have become less crucial to our survival. And yet, this virtue of the past persists, causing (some of) us to jump in fear when we see a money spider running across our keyboard.

Now, in a study published in the British Journal of Psychology, researchers have identified which animals provoke the strongest reactions of fear and disgust, and which are the most common source of animal phobias.  

To do so, the team recruited close to 2,000 online participants via a Facebook group for Czech and Slovakian volunteers, who were then asked to rate both how frightening and how disgusting they found 24 animals that commonly evoke a fear response, plus one control animal (a red panda). Just 10 of those animals received a score of more than three, signifying low-to-moderate fear and disgust levels.

Spiders were the clear winner, earning a total of 4.39 points out of 5 for fear and 4.47 points for disgust. Indeed, close to 19 percent of the volunteers expressed an extreme fear when exposed to the photo of the spider, though this may be unsurprising given the frequency of arachnophobia and spiders' ubiquity in horror and Halloween imagery.

The researchers pin their unique fear-inducing quality on various factors, including "their quirky ‘too-many-legs’ body plan", their omnipresence in our homes, their capacity for "fast unpredictable movement", and their penchant for dark hiding spots.

The runner-up was the image of a venomous viper, which inflicted the greatest fear response in almost 10 percent of volunteers. This appears to confirm the generally-held consensus that snakes and spiders are the most feared animals, at least as far as people are concerned. 

In the end, the researchers were able to categorize the animals into five groups based on the amount of fear and disgust they provoked. As well as dry, non-slimy invertebrates (which included spiders, wasps, and roaches) and snakes and lizards, the team identified mouse-like animals (mouse, rat, and bat) and farm/pet animals (horse, bull, dog, and cat etc), both of which induced low fear and disgust levels. 

The final category included human endo? and exo-parasites, i.e. parasites, which included intestinal helminths and louse. These creatures may be vectors of (potentially deadly) diseases and, therefore, perhaps unsurprisingly triggered the highest levels of disgust.

Interestingly, people with a history of animal injury (for example, dog bites) reported lower feelings of disgust and fear, though as Christian Jarett in The British Psychological Society Research Digest points out, innate lower levels of fear and disgust may have made them more likely to approach the animal that then gave them an injury in the first place.

The biggest "factor" for self-reported fear and disgust appeared to be gender, with women more likely than men to express both (a common pattern in all anxiety-related studies, the researchers point out).

It is important to add that self-reporting and the stillness of the photographs (movement in video and real-life have been proven to provoke greater fear, if not disgust) may have influenced the results. Still, if you're looking to give someone a cheap scare, we would suggest you go out and buy a rubber spider.

The red panda – a cute, fluffy, and decidedly non-scary (if just a tiny bit extra) animal – was included as a control animal. Yet, it still managed to beat cats, fish, snails, and lizards on the fear factor. Swagmiser/Youtube