What exactly IS fear?
Fear is a basic emotion. Emotions are motivational (same root word -- motion, right? They drive behavior, causing you to act -- putting you "in motion"). Other basic, universal (experienced by all people) emotions include anger, sadness, happiness, surprise, etc. Emotions includes a physiological (body)component of sympathetic nervous system activation-- fight or flight response in your body, a surge adrenaline, which gets you ready to respond quickly. This includes heart rate increase, change in blood pressure, pupil dilation, etc. There is also a cognitive part -- a thought about what caused the body's response. We avoid things we are afraid of. This can be a very good thing! Fear can be adaptive, and keep us safe, but it can be debilitating, and get in the way of our lives. Phobias are a good example of a fear that is keeping us from living our lives as we might.
What are the most common phobias?
Social phobias are the most common -- like fear of public speaking, or fear of embarrassing ourselves in public. It usually develops during the high school years, when we are very focused on what people think of us, and self-conscious that people are observing us (this is called teenage narcissism. it's totally normal, but annoying. it is what makes you not want to be seen in public with your parents when you are younger). One bad experience is enough to start this phobia, which is a learned behavior (see below).
Common specific phobias are fear of insects like spiders, fear of snakes, fear of heights, fear of confined spaces (claustrophobia), and a phobic response to blood or injections. Like many animals, we seem to be predisposed to learn fear of these things, which again, seems to be adaptive. Many people, particularly those with OCD, fear germs and contamination.
Why do some people fear one thing, and others not have issue with it?
Some people are temperamentally and even genetically more reactive (that is, more emotional, more easy to disturb, more anxious, while others are more even-tempered and less excitable). As a species, we seem to be predisposed (and hence learn easily) to fear snakes, heights, spiders, and other things that may harm us. Often, though, a fear is a result of an experience. Take PTSD, for example; it is caused by a horrific terrible uncontrollable event occurring near us, involving danger to our lives or others. That is an experience that causes fear, and the fear is then easily triggered by anything associated with the horrible event, causing the same physiological fear response.
What causes fear?
Fear is typically a learned response, through associative learning; instrumental learning (there's a bad outcome associated with something), or classical conditioning (a simple pairing of a physiological fear response with some cue). Conditioned taste aversions are typically learned in 1 trail – that is, one pairing of a food or drink with nausea results in an aversion to that food or drink for a long, long time. You probably know people who this happened to. Someone bitten by a dog as a child may become fearful of dogs.
Dr. Watson famously conditioned fear in Baby Albert. The baby used to like furry animals, but Dr. Watson banged a loud gong near the baby, scaring it, whenever a white rat was near by. The baby became fearful of the white rat, and in fact generalized the fear to all furry things (and, I suspect, Dr. Watson!). That's why the doctors don't give kids the shots -- the nurses do. Then the kids won't be afraid of the doctor! Fears are often similiarly conditioned; some things are more easily learned (like the things mentioned above -- snakes, spiders, etc.).
Also, there is social learning. Many girls learn to fear insects because they learn girls are supposed to be afraid of insects, when it is model for them - if their mothers feared insects, for example. Boys may be afraid of insects, too, but similarly learn to not show the fear, and, perhaps even by exposure, reduce the fear response (see below, therapies for fears)
In operant conditioning, in which we are reinforced (rewarded) for a fear response. It is reinforcing to flee a spider, because our fear abates, so this reinforces, or strengthens, our fear. When boys reward girls for being fearful, it reinforces that response. When boys are teased for being fearful, it punishes that response, and they become less fearful. That is a conditioned response, but as you can see, it has a social component.
Where does fear come from?
It is somewhat hard-wired, and learned. See above.
How can people overcome their fears?
Note that fear is primarily processed in the part of the brain called the Amygdala, where motivational emotions (including anger) are processed.
Phobias are very easily treated, actually! There are a number of exposure therapies that are very, very successful. Many boys have done this informally, by subjecting themselves to the feared object until the physiological sensations abate or lessen, thus reinforcing that the feared object needed not be feared. This is essentially how exposure therapies work -- as the physiological or body sensations associated with fear lessen upon exposure, which they will, we hence-forth have less fear of something, as we have learned that it is not something we need fear. In a sense, it's getting past that initial body-sensation of fear, until our body returns to a more normal resting state, in the presence of the feared object.
The study of abnormal psychology delves into the treatment of anxiety disorders, while P101 and P155 go into learning models, in which fears develop, as well as the sympathetic nervous system, that is activated when we are frightened. Treatments for fears are frequently based on learning paradigms -- the same way we teach our dogs to do tricks! Students who are troubled by anxiety or phobias can seek help at CAPS.
Source: Dr. Lisa Tomassen, senior lecturer at IU's Department of Psychological and Brain Sciences