Why do people have phobias?

The very definition of a phobia is an "irrational fear." Phobias are always overreactions to mild dangers, constant fear of rare dangers, and outright terror of things that are not dangerous at all. Because of their irrationality, it seems like phobias can't have an evolutionary purpose. But why do we have them?

It's miserable researching an article on phobias because almost ever single source has a picture of a damn spider. I don't like them. In fact, I want to stomp them flat, and only fear of karmic retribution makes me collect them in glasses and toss them into the garden.

I have no reason to fear spiders. No spider has ever harmed me, and I'm pretty sure no spider in my neck of the woods could. Spiders are part of the "animal" class of common phobias (which include snakes and rats).

Another common class of phobias are spatial ones, such as claustrophobia, agoraphobia, and acrophobia. It's not strange that these things occasionally provoke fear. It's just strange that they provoke such massive fear in some people that they aren't, by any standard, reasonable.

There is a strictly biological component to phobias. A quick look at how the brain works when phobic people are triggered suggests the problem. When worrisome stimuli get into the brain, there are two ways they can go; to the amygdala and to the sensory cortex. The sensory cortex is a calm, rational part of the brain. It casts around the rest of the brain for more information and looks at general knowledge, present context, and past experience before it reacts.

The amygdala, on the other hand, is the part of the brain that gets an unpleasant stimulus and screams, "What are you doing? Run, stupid!" When people say that phobias aren't rational, they're right. The amygdala is not there to be rational. It's there to get results. And it does, often in the form of a panic attack.

When it comes to the reasons why the amygdala is triggered at the sight of, say, a rat, the psychiatric community gives a big shrug. The top four answers are genetics, trauma, overall stress, and a combination of the three. The way science arrived at these answers is much more interesting than the answers themselves.

Some scientists look to simple genetics to see if they can find the answer to phobias. It makes sense, to an extent. Most of the things people are afraid of things like creepy-crawlies, heights, or tight enclosures. All could have caused our too-bold ancestors to die off early. It makes sense that some extreme aversion would be hard-wired into certain people.

Pure nature is tough to establish independently of that pesky thing known as nurture, however. Families are raised together, and one person's phobia can affect another's likelihood of developing the same phobia. Researchers figured the most likely way to ferret out the genetic reason behind phobias was a twin study. In the nineties and early 2000s, a group of studies found twins raised apart tended to have similar phobias.

There was a catch, though. The twins had social phobias, all related to meeting and associating with people. These social phobias sprang from other genetic disorders, like anxiety disorder and extreme introversion. Although the conditions that contributed to the phobia might have been hard-wired into the twins, the actual phobia might have been a likely effect of the already present conditions. Hardly a genetic smoking gun.

A more interesting, and sinister, experiment makes the case for both genetics and traumatic conditioning. Martin Seligman, a psychologist who made a name for himself giving dogs electric shocks to show that helplessness can be learned, turned his eyes to bigger game. He applied shocks while exposing subjects to images of certain stimuli.

He found that spiders, snakes, rats, and other unpleasant images took only about four rounds of shock treatment to produce a phobic response, even without the shocks. That seemed very much like a conditioned response, until he did the same thing with pictures of flowers and other neutral things. Although subjects did eventually become phobic of flowers, it took a much longer series of shocks to knock the scare into them. It seems that we're primed to respond to certain phobias, and unpleasant events can set us off.

Another series of experiments were performed on rhesus monkeys. The monkeys were shown to be deeply afraid of snakes in the wild, but did not fear them when raised in a lab or a domestic environment. Domesticated monkeys were rounded up and shown films of their fellow monkeys in the wild reacting fearfully. The films sometimes made it look like the wild monkeys were reacting to a snake, and sometimes to a bunch of flowers. The domesticated rhesus monkeys developed a phobia of snakes, but didn't react similarly to flowers. There's clearly something that crawls around the brain clearing a path for certain things to trigger the amygdala, but other things are harder to develop into a fear. Something primed the monkeys, but it was social conditioning that set them off.

These kinds of common phobias, prepared by whatever murky genetics and brought to the forefront of the brain by sadistic psychologists, make sense. But then what about the many strange phobias that people develop? What about the woman in the UK who suddenly was so afraid of peas that she couldn't walk down the frozen food aisle and would run out of restaurants if someone near her ordered them? What about pogonophobia, the fear of people with beards? What about the infamous fear of getting peanut butter stuck to the roof of the mouth?

The last one, actually, seems to trigger a fear of suffocation. Regular food can be swallowed or spit out, but peanut butter clings on, obstructing the mouth and making people feel like they're choking. The rest seem to be responses to a loss of control, and the stress that comes with that. When a person is put under a great deal of stress, especially if that stress comes with hormones — as with the case of the pea-fearer, who was pregnant — the mind casts around for something that has caused emotional distress. Whatever it seizes on — whether it's thunder during a storm or frozen peas or any other harmless object — triggers the amygdala and in turn provokes a panic response in the sufferer.

The list of fringe phobias is fun to scan. Aurophobia is the fear of gold. Auroraphobia is the fear of the Northern Lights. One of the more recently-named phobias is genuphobia, the fear of knees.

But are these fears as silly as they seem? A knee is more likely to do real damage to me than a spider. Peanut butter will put more people in the hospital this year than plane crashes. And at least you can slip on frozen peas, which is more than anyone can say about wide-open spaces. Some phobias, like escalators, are common, while some phobias, like pluviophobia (the fear of getting rained on) are uncommon, but they are about equally likely to hurt you. They are equally irrational causes for fear. And strangely, nobody has coined the term for a phobia of sadistic experimental psychologists and their pictures of spiders.

Top Image: National Cancer Institute. Via The BBC, AllPsych, Bryn Mawr, OSU, and the American Journal of Psychology.