In my previous blog post I described some of the research that has begun to throw light on why so many people appear to be scared of spiders. In particular, there seemed to be a significant link between being frightened of spiders and your disgust sensitivity levels. Disgust, if you remember, is a food rejection response that has evolved to prevent the transmission of disease and illness, and is a response that is usually elicited by things such as feces, mucus and vomit–things that are likely to be vehicles for the transmission of disease. However, disgust has also been shown to be associated with a range of "fear-relevant" but largely non-predatory animals (on humans at any rate). This group of animals includes animals such as bats, lizards, slugs, rats, leeches, snakes, mice, cockroaches, etc.–as well as spiders.

So this raises the question of how these animals acquired disgust relevance. I have previously argued that that there are three ways in which these animals have become "disgusting" and these are all linked to a matter of disease and illness. Some animals acquired their disgust-relevance by being directly associated with the spread of disease (e.g., rats, cockroaches), others by possessing features that resemble primary disgust-eliciting stimuli such as mucus and feces, and examples include animals that are perceived as slimy such as lizards, snakes, slugs, worms, frogs (even though they are not necessarily slimy to the touch), and finally, animals who may not spread disease directly but may act as signals for potential disease (such as maggots that are associated with putrefying food).

At first sight, the spider doesn’t appear to fit obviously into any of these categories. However, an historical analysis suggests that spiders have been associated with disease and infection in Europe for many centuries. For example, in the Middle Ages, any food that came into contact with spiders was considered to be infected, and if a spider fell into water, then that water was considered to be poisoned. Right up to the late seventeenth century, many European spiders were thought to be poisonous and to be causes of hysteria and symptoms of illness. This was known as “tarantism”, and various forms of tarantism have been described in Sicily, Spain, Germany, Persia, Asia Minor, America and Albania. However, while the bites of some European spiders can cause systemic reactions, these bites were not the causes of many of the symptoms that they were blamed for! Similarly, in many parts of Europe during the Middle Ages, spiders were also perceived as harbingers of the Great Plagues that swept across Europe from the tenth century onwards. It was only discovered in the nineteenth century that it was the black rat that carried the fleas that spread the plague, but it is perhaps no coincidence that spiders were also found in those parts of a house occupied by the black rat (e.g., thatched roofs).

If all this is true, then the spider has acquired its disgust and disease relevance by accident, and this may be a cultural phenomenon largely restricted to Europeans and passed on to their descendants. This raises two immediate questions. First, how is this "fear" of the disgusting spider passed on from generation to generation, and secondly, if it has its origins in European culture, we would not expect spider phobia to be a universal phenomenon, and it should be found primarily in Europeans and their descendants.

In relation to the first question, it has been known for many years that spider phobia tends to run in families. It has often been assumed that this may represent a biological predisposition caused by the transmission of genes between parents and offspring. However, we found that this relationship was considerably more complex and indirect. We found that the only significant predictor of a child’s spider fear was not the level of spider fear in the parents, but their levels of disgust sensitivity. One interpretation of this finding is that spider fear may be transmitted within families as the result of social learning of the nature and intensity of disgust reactions–including disgust reactions to spiders.

Secondly, spider phobia is far from being a universal phenomenon (albeit, popular science fiction films such as Arachnophobia may contribute to making it a more universal phenomenon than it may once have been!). In many areas of the world, such as Indo-China, the Caribbean, Africa, and amongst the Native Americans of North America and the aborigines of Australia, spiders are eaten as a delicacy. In addition, many cultures consider spiders to be symbols of good fortune rather than fear (e.g., Hindu culture). In support of this, a cross-cultural study of animal phobias we conducted suggested that there were significant cultural differences in fear towards the spider. While countries populated by Europeans and their descendants exhibited high levels of spider fear, this was significantly less apparent in some non-European countries, such as India.

Having said all this, I should point out that there are many other researchers who believe that spider phobia is not purely a cultural phenomenon, but may be in some way genetically pre-wired. Nevertheless, the link between the spider and the disgust emotion, and the significant cultural variation in the prevalence of spider phobia, suggest a more complex, and intriguing, origin for fear of spiders.

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