Signs and symptomsEdit
People with arachnophobia tend to feel uneasy in any area they believe could harbor spiders or that has visible signs of their presence, such as webs. If arachnophobics see a spider, they may not enter the general vicinity until they have overcome the panic attack that is often associated with their phobia. Some people scream, cry, have emotional outbursts, experience trouble breathing, sweat, have heart palpitations, or even faint when they come in contact with an area near spiders or their webs. In some extreme cases, even a picture or a realistic drawing of a spider can trigger intense fear.
An evolutionary reason for the phobia remains unresolved. One view, especially held in evolutionary psychology, is that the presence of venomous spiders led to the evolution of a fear of spiders or made acquisition of a fear of spiders especially easy. Like all traits, there is variability in the intensity of fears of spiders, and those with more intense fears are classified as phobic. Spiders, for instance, being relatively small, do not fit the usual criterion for a threat in the animal kingdom where size is a factor, but they can have medically significant venom. However, This theory fails to take into consideration that a phobia is an irrational fear as opposed to a rational fear, in the context of current mental health usage. 
By ensuring that their surroundings were free from spiders, arachnophobes would have had a reduced risk of being bitten in ancestral environments, giving them a slight advantage over non-arachnophobes in terms of survival. However, having a disproportional fear of spiders in comparison to the other, potentially dangerous creatures that were present during Homo sapiens' environment of evolutionary adaptiveness may have had drawbacks.
A 2001 study found that people could detect images of spiders among images of flowers and mushrooms more quickly than they could detect images of flowers or mushrooms among images of spiders. The researchers suggested that this was because fast response to spiders was more relevant to human evolution.
The alternative view is that the dangers, such as from spiders, are overrated and not sufficient to influence evolution. Instead, inheriting phobias would have restrictive and debilitating effects upon survival, rather than being an aid. For some communities such as in Papua New Guinea, Cambodia and South America (except Chile, Colombia, Brazil, Uruguay, Argentina and Bolivia), spiders are included in traditional foods. This suggests arachnophobia may be a cultural, rather than genetic trait.
The fear of spiders can be treated by any of the general techniques suggested for specific phobias. The first line of treatment is systematic desensitization – also known as exposure therapy – which was first described by South African psychiatrist Joseph Wolpe. Before engaging in systematic desensitization it is common to train the individual with arachnophobia in relaxation techniques, which will help keep the patient calm. Systematic desensitization can be done in vivo (with live spiders) or by getting the individual to imagine situations involving spiders, then modelling interaction with spiders for the person affected and eventually interacting with real spiders. This technique can be effective in just one session.
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