Fear

Fear is a distressing emotion aroused by a perceived threat. It is a basic survival mechanism occurring in response to a specific stimulus, such as pain or the threat of danger. Some psychologists such as John B. Watson, Robert Plutchik, and Paul Ekman have suggested that fear belongs to a small set of basic or innate emotions. This set also includes such emotions as joy, sadness, and anger. Fear should be distinguished from the related emotional state of anxiety, which typically occurs without any external threat. Additionally, fear is related to the specific behaviors of escape and avoidance, whereas anxiety is the result of threats which are perceived to be uncontrollable or unavoidable. Worth noting is that fear almost always relates to future events, such as worsening of a situation, or continuation of a situation that is unacceptable. Fear could also be an instant reaction to something presently happening.

Description
A vivid description of fear was provided by Charles Darwin in his book, The Expression of the Emotions in Man and Animals:

Fear is often preceded by astonishment, and is so far akin to it, that both lead to the senses of sight and hearing being instantly aroused. In both cases the eyes and mouth are widely opened, and the eyebrows raised. The frightened man at first stands like a statue motionless and breathless, or crouches down as if instinctively to escape observation. The heart beats quickly and violently, so that it palpitates or knocks against the ribs... That the skin is much affected under the sense of great fear, we see in the marvelous manner in which perspiration immediately exudes from it... The hairs also on the skin stand erect; and the superficial muscles shiver. In connection with the disturbed action of the heart, the breathing is hurried. The salivary glands act imperfectly; the mouth becomes dry, and is often opened and shut.

The most common physical reactions of fear include:
 * Rapid heart rate
 * Increased blood pressure
 * Tightening of muscles
 * Sharpened or redirected senses
 * Dilation of the pupils (to let in more light)
 * Increased sweating

The facial expression of fear includes the widening of the eyes (out of anticipation for what will happen next); the pupils dilate (to take in more light); the upper lip rises, the brows draw together, and the lips stretch horizontally. The physiological effects of fear can be better understood from the perspective of the sympathetic nervous responses (fight-or-flight), as compared to the parasympathetic response, which is a more relaxed state. Muscles used for physical movement are tightened and primed with oxygen, in preparation for a physical fight-or-flight response. Perspiration occurs due to blood being shunted from body's viscera to the peripheral parts of the body. Blood that is shunted from the viscera to the rest of the body will transfer, along with oxygen and nutrients, heat, prompting perspiration to cool the body. When the stimulus is shocking or abrupt, a common reaction is to cover (or otherwise protect) vulnerable parts of the anatomy, particularly the face and head. When a fear stimulus occurs unexpectedly, the victim of the fear response could possibly jump or give a small start. The person's heart-rate and heartbeat may quicken.

Varieties
Fear can be widely classified into two types: external fear and internal fear.
 * External fear is caused by something outside of you which you are strongly motivated to avoid, for example: fear of spiders.
 * Internal fear is something outside of you that you link a negative emotion, for example: fear developed out of low self esteem.

Fear can be described with different terms in relation to the degree of fear that is experienced. It varies from mild caution to extreme phobia and paranoia. Fear is related to a number of additional cognitive and emotional states including worry, anxiety, terror, horror, panic, and dread. Experiences of fear can remain long after exposure in the unconscious mind, where they may then manifest as nightmares, or, in an even stronger form, night terrors. Fear may also be experienced within a larger group or social network, and may be compounded by social influence and become mass hysteria. Some pathologies related to fear (defined by persistent and irrational fears) can include different types of anxiety disorder which are very common, and also other more severe illnesses like the extreme phase of bipolar disorder and some kinds of schizophrenia.

The experience of distrust can be explained as a feeling of mild fear or caution, usually in response to an unfamiliar or potentially dangerous person. Distrust may occur as a feeling of warning towards someone or something that is questionable or unknown. For example, one may distrust a stranger who acts in a way that is perceived as odd or unusual. Likewise, one may distrust the safety of a rusty old bridge across a 1000-foot drop. Distrust may serve as an adaptive, early warning signal for situations that could lead to greater fear and danger. Reassurance can usually dissolve a fear like this e.g. repeatedly doing something to gain trust in it.

Terror is an acute and pronounced form of fear. It is an overwhelming sense of immediate personal danger. It can also be caused by perceiving the object of a phobia. Terror may overwhelm a person to the point of making irrational choices and atypical behavior. Paranoia is a term used to describe a psychosis of fear. It is experienced as long-standing feelings and perceptions of being persecuted. Paranoia is an extreme emotional state combined with cognitions or, more specifically, delusions that one is in danger. This degree of fear may indicate that a person has changed his or her normal behavior in extreme or maladaptive ways.

Common fears
According to surveys, some of the most common fears are of: ghosts, the existence of evil powers, cockroaches, spiders, snakes, heights, water, enclosed spaces, tunnels and bridges, needles, social rejection, failure, examinations and public speaking. In an innovative test of what people fear the most, Bill Tancer analyzed the most frequent online search queries that involved the phrase, "fear of...". This follows the assumption that people tend to seek information on the issues that concern them the most. His top ten list of fears consisted of flying, heights, clowns, intimacy, death, rejection, people, snakes, success, and driving.

Another common fear can be the fear of public speaking. People may be expertised speakers inside a room but when it becomes public speaking, fear enters in the form of suspicion that whether the words uttered are correct or wrong because there are many to judge it.

Another common fear can be of pain, or of someone damaging a person. Fear of pain in a plausible situation brings flinching, or cringing.

In a 2005 Gallup poll (U.S.A.), a national sample of adolescents between the ages of 13 and 15 were asked what they feared the most. The question was open ended and participants were able to say whatever they wanted. The most frequently cited fear (mentioned by 8% of the teens) was terrorism. The top ten fears were, in order: terrorist attacks, spiders, death, being a failure, war, heights, criminal or gang violence, being alone, the future, and nuclear war.

Causes
People develop specific fears as a result of learning. This has been studied in psychology as fear conditioning, beginning with John B. Watson's Little Albert experiment in 1920. In this study, an 11-month-old boy was conditioned to fear a white rat in the laboratory. The fear became generalized to include other white, furry objects. In the real world, fear can be acquired by a frightening traumatic accident. For example, if a child falls into a well and struggles to get out, he or she may develop a fear of wells, heights (acrophobia), enclosed spaces (claustrophobia), or water (aquaphobia). There are studies looking at areas of the brain that are affected in relation to fear. When looking at these areas (amygdala), it was proposed that a person learns to fear regardless of whether they themselves have experienced trauma, or if they have observed the fear in others. In a study completed by Andreas Olsson, Katherine I. Nearing and Elizabeth A. Phelps the amygdala were affected both when subjects observed someone else being submitted to an aversive event, knowing that the same treatment awaited themselves, and when subjects were subsequently placed in a fear-provoking situation. This suggests that fear can develop in both conditions, not just simply from personal history.

Although fear is learned, the capacity to fear is part of human nature. Many studies have found that certain fears (e.g. animals, heights) are much more common than others (e.g. flowers, clouds). These fears are also easier to induce in the laboratory. This phenomenon is known as preparedness. Because early humans that were quick to fear dangerous situations were more likely to survive and reproduce, preparedness is theorized to be a genetic effect that is the result of natural selection.

The experience of fear is affected by historical and cultural influences. For example, in the early 20th Century, many Americans feared polio, a disease that cripples the body part it affects, leaving that body part immobilized for the rest of one's life. There are also consistent cross-cultural differences in how people respond to fear. Display rules affect how likely people are to show the facial expression of fear and other emotions.

Neurobiology
The amygdala is a key brain structure in the neurobiology of fear. It is involved in the processing of negative emotions (such as fear and anger). Researchers have observed hyperactivity in the amygdala when patients were shown threatening faces or confronted with frightening situations. Patients with a more severe social phobia showed a correlation with increased response in the amygdala. Studies have also shown that subjects exposed to images of frightened faces, or faces of people from another race, exhibit increased activity in the amygdala.

The fear response generated by the amygdala can be mitigated by another brain region known as the rostral anterior cingulate cortex, located in the frontal lobe. In a 2006 study at Columbia University, researchers observed that test subjects experienced less activity in the amygdala when they consciously perceived fearful stimuli than when they unconsciously perceived fearful stimuli. In the former case, they discovered the rostral anterior cingulate cortex activates to dampen activity in amygdala, granting the subjects a degree of emotional control.

The role of the amygdala in the processing of fear-related stimuli has been questioned by research upon those in which it is bilateral damaged. Even in the absence of their amygdala, they still react rapidly to fearful faces.

Suppression of amygdala activity can also be achieved by pathogens. Rats infected with the toxoplasmosis parasite become less fearful of cats, sometimes even seeking out their urine-marked areas. This behavior often leads to them being eaten by cats. The parasite then reproduces within the body of the cat. There is evidence that the parasite concentrates itself in the amygdala of infected rats.

It must be noted that several brain structures other than the amygdala have also been observed to be activated when individuals are presented with fearful vs. neutral faces, namely the occipitocerebellar regions including the fusiform gyrus and the inferior parietal / superior temporal gyri. Interestingly, fearful eyes, brows and mouth seem to separately reproduce these brain responses.

Fear and death
Psychologists have addressed the hypothesis that fear of death motivates religious commitment, and that it may be alleviated by assurances about an afterlife. Empirical research on this topic has been equivocal. According to Kahoe and Dunn, people who are most firm in their faith and attend religious services weekly are the least afraid of dying. People who hold a loose religious faith are the most anxious, and people who are not religious are intermediate in their fear of death. A survey of people in various Christian denominations showed a positive correlation between fear of death and dogmatic adherence to religious doctrine. In other words, Christian fundamentalism and other strict interpretations of the Bible are associated with greater fear of death. Furthermore, some religious orientations were more effective than others in allaying that fear.

In another study, data from a sample of white, Christian men and women were used to test the hypothesis that traditional, church-centered religiousness and de-institutionalized spiritual seeking are distinct ways of approaching fear of death in old age. Both religiousness and spirituality were related to positive psychosocial functioning, but only church-centered religiousness protected subjects against the fear of death.

Fear of death is also known as death anxiety. This may be a more accurate label because, like other anxieties, the emotional state in question is long lasting and not typically linked to a specific stimulus. The analysis of fear of death, death anxiety, and concerns over mortality is an important feature of existentialism and terror management theory.