Phobias are a psychological phenomenon where a person has an extreme fear of something that doesn't pose a serious threat. These fears can be towards things such a spiders or snakes, or even something less threatening like fish or even certain foods.
Whatever the object of the fear, all phobias can be severely debilitating and are a serious problem that requires treatment. The key thing that differentiates phobias from fears is that they are irrational, meaning that the object of phobias pose no real threat.
Though the origins of phobias have yet to be totally explained, it is thought that they form in a manner similar to the famous "Pavlov's Dog" situation, also known as "classical conditioning".
Essentially, the Pavlov's dog phenomenon involves a dog producing a reflexive behaviour towards a trained stimulus. For the dog, this reflex was salivating. Since salivating is a natural reflex in response to food, whenever the dog was presented with food, it would begin to salivate. Pavlov decided to ring a bell each time the dog was presented with food. Eventually, the dog begins to reflexively salivate to the sound of the bell even if food is not presented. This same situation can be extended to humans.
Let's take agoraphobia as an example. This type of phobia is a fear of being in open public places. It is usually found in people who suffer from panic attacks, which is a separate anxiety disorder that occurs at random times and gives symptoms similar to a heart attack. If a person goes into a public place and happens to have an anxiety attack, their brain can link these two situations. Now, just like Pavlov's dog learned to salivate to the bell, the person learns to be afraid of open places because they're afraid it'll trigger another panic attack.
This same principle can be applied to any stimulus. A famous experiment with a baby, which the scientific literature refers to as "Little Albert", tested this. They presented the baby with a small fuzzy white rat, which a baby normally would not be afraid of. But in their experience, they crashed a loud cymbal near the baby each time the rat was shown. The baby quickly associated the fuzzy white rat with the loud, frightening noise, and the baby began to become very frightened each time he saw the rat. Surprisingly, the baby also showed incredible fear when presented with other white objects, such as a teddy bear.
Using the Pavlonian model of classical conditioning, it is quite easy to explain how phobias form. But by using the same model, it is possible to treat people with these disorders. If a person can learn to be afraid of an object, it is also possible for that person to learn to be unafraid of that same object. This is done by a treatment known as "systematic desensitization".
When using this treatment, a therapist teaches the patient various relaxation techniques. This could involve calming imagery, muscle relaxation techniques, or other forms of anxiety reduction. Once the patient has mastered these techniques, the therapist asks the patient to imagine the object of their phobia.
So if they have arachnophobia (fear of spiders), they picture a big spider in their mind. Instead of being afraid, however, the patient is encouraged to practice their relaxation techniques while picturing the spider. Eventually, the mental image of a spider no longer causes them anxiety.
The next step is to increase the reality of the stimulus. The therapist may present the patient with a photograph of a spider, and again encourage them to practise their relaxation techniques. Eventually, they will increase the reality of the stimulus until the patient actually hold a real live spider in their hands. It is thought that by exposing the patient to their fears while practising relaxation techniques, the patient will learn to relax in the presence of that object instead of being afraid. This technique has been shown to be quite effective for many different phobias.
As a whole, the Pavlonian classical conditioning model does a good job explaining the origins of phobias. While there are certain exceptions to this model, it is fairly well accepted that the majority of phobias form in this pattern. Since we now understand how these phobias form, we were able to develope treatments, such as systematic desensitization, to effectively treat these disorders and bring great relief to those who suffer from it.