By Christian Jarrett

You may be best advised not to read this article late at night or before you eat. Psychologists at the National Institute of Mental Health and Charles University in the Czech Republic have surveyed a large sample of non-clinical volunteers to gauge their reaction to 24 creatures that are commonly the source of specific animal phobias.

The results, published in the British Journal of Psychology, not only contribute to our understanding of animal phobias, but could prove incredibly useful to horror writers. Among the key findings is that spiders were unique in being both intensely fear- and disgust-inducing in equal measure. The researchers said this may be due to their mix of disgusting properties – including their “quirky ‘too-many-legs’ body plan” – combined with the fact they are “…omnipresent in our homes, often lurking in the hidden dark places and capable of fast unpredictable movement.” In other words, the intense fear arises in part from the prospect of coming into physical contact with a creature perceived by many to be revolting.

Jakub Polák and his team recruited nearly 2000 people online and asked them to rate how frightening and disgusting they found 25 creatures, including – alongside the spider – a snail, dog, bull, maggot, cockroach, two kinds of snake (a viper and a grass snake), and ant. See the image above for the full list.

Depicted in photographs on-screen, this particular selection of species – aside from the red panda, which acted as a non-fear-inducing control – was chosen because they are frequently the source of animal phobias.

Categorising the creatures based on the levels of fear and disgust that they elicited, the researchers identified five groupings: fear-relevant, non-slimy small animals, such as cockroaches, ants and wasps; mouse-like animals, such as mouse, rat and bat, which scored low on elicited fear and disgust; snakes and lizards; parasites, such as lice and tapeworm, which triggered high disgust; and finally, farm or pet mammals, such as cat, dog and horse, which generally elicited low fear and disgust.

One explanation for common animal phobias is that they reflect an exaggerated, uncontrolled form of innate fears for certain creatures that we all share, particularly for creatures that imperilled our ancestors, such as spiders and snakes. Consistent with this evolutionary account, spiders and venomous snakes elicited the strongest fear reactions among the participants, while parasites elicited the strongest disgust reactions (consistent with the idea that disgust motivates a form of protective “behavioural avoidance”). However, less consistent with the evolutionary perspective on animal phobias is that 14 of the creatures elicited virtually no fear, including rats, mice and lizards, even though these animals are commonly the source of phobias.

The researchers noted that, similar to spiders, the parasitic creatures like tape-worm and roundworm were both highly disgust-inducing (even more than the spider) while at the same time being rated as highly fear-inducing (even more than, say, the wasp or grass-snake). Perhaps, the researchers reasoned, this combined fear and disgust reaction to intestinal parasites has evolved because they infect us with microscopic larvae meaning we rarely see them with our eyes, yet we are aware they are omnipresent. Once again, as with spiders, we cannot rely only on disgust (and behavioural avoidance) to protect us, and so we also fear unwanted physical contact. The maggot, by contrast, may elicit less fear because it can be seen and avoided more easily.

Some other details to emerge from the study are that women generally gave higher fear and disgust ratings than men, and especially for non-slimy invertebrates and repulsive human parasites – this may be in line with evolutionary theory because “women as a sex with higher reproductive cost need to be extra careful of pathogens threatening not only their health but also the [health] of their children.”

Also, the researchers asked their participants about any past traumatic experiences with animals, such as being seriously bitten by a dog or scratched by a cat. Surprisingly perhaps, they found that fear ratings were lower among people with such a bad experience in their past. However, this correlation makes sense if you consider that people with a greater fear of animals may be be more cautious and less likely to get hurt. “Our results … suggest that fear and disgust could protect subjects against harm even in our modern environment,” the researchers said. In excess, fear can be debilitating and unwelcome, but this last result is perhaps a reminder that it is also there to serve a purpose – including to protect us from the creatures that may bite us while we sleep or infect us from within.

—Scary and nasty beasts: Self‐reported fear and disgust of common phobic animals

Christian Jarrett (@Psych_Writer) is Editor of BPS Research Digest