Verified by 
Who's afraid of spiders? Well, quite a lot of people it seems. Spider phobia is one of the most prolific of the specific phobias and it afflicts people across a range of geographical and cultural boundaries. As many as 1 in 3 women are fearful of spiders and the same figures are probably also true of men–but men are much less likely to admit it!
So let's get to the main question. Why are so many people frightened of spiders? They hardly pose a danger to people–there are around 35,000 different species of spiders currently inhabiting the earth, yet as few as just around a dozen of these pose a lethal threat to humans. Indeed, in the U.S., ten times more people die from bee stings than from spider bites. Surely from the animal world it would be more adaptive to be frightened of bears, tigers, sharks, and even dogs–but relatively few people ever develop clinical phobias of these animals. In fact we even send our children to bed with cuddly versions of these (especially teddy bears)! In contrast, many people develop very severe fears to spiders–even to the extent of being unable to even look at a photo of these creatures, or even listen to the word "spider"!
So why is spider phobia so popular and where does it come from? The first clue is that people who fear spiders are also more likely to fear a whole group of other animals that we call "fear relevant". This group of "fear relevant" animals consists of many small mammals, such as rats and mice, animals that tend to have a slimy appearance, such as amphibians, snakes and lizards, and insects and invertebrates such as slugs, snails, cockroaches, and other creepy-crawlies.
So what's the common factor that makes people frightened of this rather motley collection of animals? The answer is the disgust emotion. All of these animals elicit disgust, and the stronger your own disgust reaction, the more you will dislike these animals.
The disgust emotion is a response that has evolved to prevent the spread of disease and illness, and primary disgust eliciting stimuli are things like mucus, feces and vomit–all of which may carry pathogens that could spread disease. We react to these types of stimuli by avoiding touching them, by feeling nauseous, by making sure we do not put them in our mouth or ingest them, we also have a distinctive facial expression that conveys disgust, and this involves a wrinkling of the nose (to prevent smells and pathogens being inhaled) and a down turning of the corners of the mouth (so that anything already in the mouth is likely to drain out and also not be ingested).
Many studies have shown that people who fear "fear-relevant animals"–including spiders–possess a significantly higher disgust sensitivity; that is, they react more strongly to disgusting things, and dislike them more. This is also true of people who are spider phobic. We carried out a study a number of years ago asking spider phobics to tell us what it was about spiders that frightened them. Interestingly, there was no consensus as to what it was about spiders that was frightening. Some people feared their hairiness, others their legs, others the fact that they tended to move quickly and unpredictably, still others didn’t like their eyes, and thought that spiders were "staring at them". This lack of consensus among spider phobics about what is frightening suggests that the real cause of spider fear is hidden, and is something that spider phobics are not immediately aware of. It turns out that this hidden factor may well be disgust, and research has shown that level of spider fear is related to levels of sensitivity to disgust, and that treatment for spider phobia progresses more successfully if disgust responses are also targeted in treatment.
All of this suggests that many animal phobias represent disgust reactions rather than spine-chilling fear in the traditional sense. But this begs the question of why certain animals elicit disgust and others don't, and in particular why spiders elicit disgust, and why they've become arguably the most feared animal in the world!
The answer probably lies in an historical analysis of how these individual animals have been associated with the spread of disease amongst humans. This is another interesting and revealing analysis–especially in the case of spiders, and I'll provide some further information on this in my next post in the next few days.
