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Fear is an emotion induced by a threat perceived by living entities, which causes a change in brain and organ function and ultimately a change in behavior, such as running away, hiding or freezing from traumatic events. Fear may occur in response to a specific stimulus happening in the present, or to a future situation, which is perceived as risk to health or life, status, power, security, or in the case of humans wealth or anything held valuable. The fear response arises from the perception of danger leading to confrontation with or escape from/avoiding the threat (also known as the fight-or-flight response), which in extreme cases of fear (horror and terror) can be a freeze response or paralysis.

In humans and animals, fear is modulated by the process of cognition and learning. Thus fear is judged as rational or appropriate and irrational or inappropriate. An irrational fear is called a phobia.

Psychologists such as John B. Watson, Robert Plutchik, and Paul Ekman have suggested that there is only a small set of basic or innate emotions and that fear is one of them. This hypothesized set includes such emotions as joy, sadness, fright, dread, horror, panic, anxiety, acute stress reaction and anger.

Fear should be distinguished from, but is closely related to, the emotion anxiety, which occurs as the result of threats which are perceived to be uncontrollable or unavoidable.<ref>Öhman, A. (2000). "Fear and anxiety: Evolutionary, cognitive, and clinical perspectives". In M. Lewis & J. M. Haviland-Jones (Eds.). Handbook of emotions. pp. 573–593. New York: The Guilford Press.</ref>

The fear response serves survival by generating appropriate behavioral responses, as it has been preserved throughout evolution.<ref name=Olsson>Template:Cite doi</ref>

Etymology

The noun fear stems from the Middle English feer, fere, fer, the Old English fǣr for 'calamity, danger' (and its verb fǣran 'frighten', but also 'revere') is related to the Proto-Germanic fērą 'danger', the Proto-Indo-European *per- 'to attempt, try, research, risk'. Fear is translated into German with Gefahr, into Dutch with gevaar, into Swedish with fara, into Albanian with frikë, and into Latin with perīculum, which is the root for the term in the Romanic languages.<ref name=wiktionary>Template:Cite web</ref>

The noun fear can be used in three ways with different meanings: In the uncountable form fear is a strong, uncontrollable, unpleasant emotion caused by actual or perceived danger, e.g. 'He was struck by fear on seeing the snake'. In the countable form, and when used with the indefinite article "a fear" means a phobia, a sense of fear induced by something or someone, e.g. 'Not everybody has the same fears; I have a fear of ants.' In an uncountable form it can also mean extreme veneration or awe, as toward a supreme being or deity.<ref name=wiktionary/>

Types

Top 10 types of fear in the U.S.

In a 2005 Gallup poll (U.S.A.), a national sample of adolescents between the ages of 13 and 17 were asked what they feared the most. The question was open-ended and participants were able to say whatever they wanted. The top ten fears were, in order: terrorist attacks, spiders, death, being a failure, war, criminal or gang violence, being alone, the future, and nuclear war.<ref>[http://www.gallup.com/poll/15439/What-Frightens-Americas-Youth.aspx Gallup Poll: What Frightens America's Youth], gallup.com (29 March 2005).</ref>

In an estimate of what people fear the most, book author Bill Tancer analyzed the most frequent online queries that involved the phrase, "fear of..." following the assumption that people tend to seek information on the issues that concern them the most. His top ten list of fears published 2008 consisted of flying, heights, clowns, intimacy, death, rejection, people, snakes, failure, and driving.<ref>{{#invoke:citation/CS1|citation |CitationClass=book }}</ref>

Common phobias

Template:See also According to surveys Template:Citation needed, some of the most common fears are of demons and ghosts, the existence of evil powers, cockroaches, spiders, snakes, heights, water, enclosed spaces, tunnels, bridges, needles, social rejection, failure, examinations and public speaking.

One of the most common fears in humans is the fear of public speaking. People may be comfortable speaking inside a room but when it becomes public speaking, fear enters in the form of suspicion over whether the words uttered are correct or incorrect because there are many to judge them. Another common fear can be of pain, or of someone damaging a person. Fear of pain in a plausible situation brings flinching, or cringing.

Fear of survival

According to Irfan Jamil, coadjutor bishop of Lahore, as the world constantly changes, the greatest fear is the fear of survival. The social, economical, spiritual, political and educational circumstances in life make survival difficult in regard to such pressures that can come out of it.<ref name="Fear not">Jamil, Irfan (25 December 2012). [http://www.nation.com.pk/pakistan-news-newspaper-daily-english-online/national/25-Dec-2012/fear-not Fear not], "The Nation".</ref> Template:Better source

Fear of death

Death anxiety is multidimensional; it covers "fears related to one's own death, the death of others, fear of the unknown after death, fear of obliteration, and fear of the dying process, which includes fear of a slow death and a painful death".<ref name="Fry">Template:Cite journal</ref>

The Yale philosopher Shelly Kagan examined fear of death in a 2007 Yale open course <ref>[http://oyc.yale.edu/philosophy/phil-176/lecture-22 Lecture 22: Fear of Death] in [http://oyc.yale.edu/philosophy/phil-176 PHIL 176: Death] Yale Open Course 2007</ref> by examining the following questions: Is fear of death a reasonable appropriate response? What conditions are required and what are appropriate conditions for feeling fear of death? What is meant by fear, and how much fear is appropriate? According to Kagan for fear in general to make sense, three conditions should be met: the object of fear needs to be "something bad", there needs to be a non-negligible chance of the bad state of affairs to happen, and there needs to be some uncertainty about the bad state of affairs. The amount of fear should be appropriate to the size of "the bad". If the 3 conditions aren't met, fear is an inappropriate emotion. He argues, that death does not meet the first two criteria, even if death is a "deprivation of good things" and even if one believes in a painful afterlife. Because death is certain, it also does not meet the third criteria, but he grants that the unpredictability of when one dies may be cause to a sense of fear.

In a 2003 study of 167 women and 121 men, aged 65–87, low self-efficacy predicted fear of the unknown after death and fear of dying for women and men better than demographics, social support, and physical health. Fear of death was measured by a "Multidimensional Fear of Death Scale" which included the 8 subscales Fear of Dying, Fear of the Dead, Fear of Being Destroyed, Fear of Significant Others, Fear of the Unknown, Fear of Conscious Death, Fear for the Body After Death, and Fear of Premature Death. In hierarchical multiple regression analysis the most potent predictors of death fears were low "spiritual health efficacy", defined as beliefs relating to one's perceived ability to generate spiritually based faith and inner strength, and low "instrumental efficacy", defined as beliefs relating to one's perceived ability to manage activities of daily living.<ref name="Fry"/>

Psychologists have tested the hypothesis that fear of death motivates religious commitment, and assurances about an afterlife alleviate the fear and empirical research on this topic has been equivocal.Template:Citation needed Religiosity can be related to fear of death when the afterlife is portrayed as time of punishment. "Intrinsic religiosity", as opposed to mere "formal religious involvement" has been found to be negatively correlated with death anxiety (reviewed in.<ref name="Fry"/>

In a 1976 study people of various Christian denominations those most firm in their faith, attending religious services weekly were the least afraid of dying. The survey found a negative correlation between fear of death and "religious concern".<ref>Template:Cite journal</ref>Template:Better source

In a 2006 study of white, Christian men and women the hypothesis was tested that traditional, church-centered religiousness and de-institutionalized spiritual seeking are 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.<ref>Template:Cite journal</ref>Template:Better source

Fear of the unknown

Many people are scared of the "unknown."Template:Citation needed The unknown can branch out to many areas such as the hereafter, the next ten years, or even tomorrow. Many people are too scared to take the path they want to, because of what may lie ahead. Fear of the unknown is one of the reasons that people do not make an effort to enhance their scholarly education. However, if they do, most people would rather teach things they've been taught than go and do research on something new. They perceive this as a risk that may cause them fear and stress.<ref name=Burton>Template:Cite journal</ref> This can lead to habits such as procrastination.Template:Better source

Fear of uncertainty and unpredictability

The stress of living in a constantly unpredictable environment can cause anxiety, other psychological problems and physical problems. People can develop fear to uncertainty. Parents tell their children not to talk to strangers in order to protect them. However, some research suggests we should not fear strangers, but be mindful of the risks that they could pose on children.<ref>Fear of the unknown.E R Fox Western Journal of Medicine 07/1987. doi|10.1108/17578043200800026.</ref>Template:Better source

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, which was inspired after observing a child with an irrational fear of dogs. 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, such as a rabbit, dog, and even a ball of cotton.

Fear can be learned by experiencing or watching 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 (such as the 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.<ref>Template:Cite pmid</ref> This suggests that fear can develop in both conditions, not just simply from personal history.

Fear is affected by cultural and historical context. 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.Template:Citation needed There are consistent cross-cultural differences in how people respond to fear.Template:Citation needed Display rules affect how likely people are to show the facial expression of fear and other emotions.

Although many fears are learned, the capacity to fear is part of human nature. Many studies Template:Citation needed 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 Template:Citation needed.

From an evolutionary psychology perspective, different fears may be different adaptations that have been useful in our evolutionary past. They may have developed during different time periods. Some fears, such as fear of heights, may be common to all mammals and developed during the mesozoic period. Other fears, such as fear of snakes, may be common to all simians and developed during the cenozoic time period. Still others, such as fear of mice and insects, may be unique to humans and developed during the paleolithic and neolithic time periods (when mice and insects become important carriers of infectious diseases and harmful for crops and stored foods).<ref>Template:Cite doi</ref>

Fear is high only if the observed risk and seriousness both are high, and is low, if risk or seriousness is low.<ref>Fear of Victimization: A Look at the Proximate Causes. Social Forces (1983) 61 (4): 1033-1043 doi|10.1093/sf/61.4.1033</ref>

Symptoms and signs of fear

Many physiological changes in the body are associated with fear, summarized as the fight-or-flight response. An inborn response for coping with danger, it works by accelerating the breathing rate (hyperventilation), heart rate, constriction of the peripheral blood vessels leading to blushing and vasodilation of the central vessels (pooling), increasing muscle tension including the muscles attached to each hair follicle to contract and causing "goose bumps", or more clinically, piloerection (making a cold person warmer or a frightened animal look more impressive), sweating, increased blood glucose (hyperglycemia), increased serum calcium, increase in white blood cells called neutrophilic leukocytes, alertness leading to sleep disturbance and "butterflies in the stomach" (dyspepsia). This primitive mechanism may help an organism survive by either running away or fighting the danger.<ref>Template:Cite web</ref> With the series of physiological changes, the consciousness realizes an emotion of fear.

Fear in animals

Often laboratory studies with rats are conducted to examine the acquisition and extinction of conditioned fear responses.<ref>Template:Cite journal</ref> In 2004, researchers conditioned rats (rattus norvegicus) to fear a certain stimulus, through electric shock.<ref>Template:Cite journal</ref> The researchers were able to then cause an extinction of this conditioned fear, to a point that no medications or drugs were able to further aid in the extinction process. However the rats did show signs of avoidance learning, not fear, but simply avoiding the area that brought pain to the tests rats. The avoidance learning of rats is seen as a conditioned response, and therefore the behavior can be unconditioned, as supported by the earlier research. Species-specific defense reactions (SSDRs) or avoidance learning in nature is the specific tendency to avoid certain threats or stimuli, it is how animals survive in the wild. Humans and animals both share these species-specific defense reactions, such as the flight, fight, which also include pseudo-aggression, fake or intimidating aggression, freeze response to threats, which is controlled by the sympathetic nervous system. These SSDRs are learned very quickly through social interactions between others of the same species, other species, and interaction with the environment.<ref>{{#invoke:citation/CS1|citation |CitationClass=book }}</ref> These acquired sets of reactions or responses are not easily forgotten. The animal that survives is the animal that already knows what to fear and how to avoid this threat. An example in humans is the reaction to the sight of a snake, many jump backwards before cognitively realizing what they are jumping away from, and in some cases it is a stick rather than a snake.

As with many functions of the brain, there are various regions of the brain involved in deciphering fear in humans and other nonhuman species.<ref>Template:Cite web</ref> The amygdala communicates both directions between the prefrontal cortex, hypothalamus, the sensory cortex, the hippocampus, thalamus, septum, and the brainstem. The amygdala plays an important role in SSDR, such as the ventral amygdalofugal, which is essential for associative learning, and SSDRs are learned through interaction with the environment and others of the same species. An emotional response is created only after the signals have been relayed between the different regions of the brain, and activating the sympathetic nervous systems; which controls the [http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2489204/ flight, fight, freeze, fright, and faint] response.<ref>Template:Cite journal</ref> Often a damaged amygdala can cause impairment in the recognition of fear.<ref>Template:Cite journal</ref> This impairment can cause different species to lack the sensation of fear, and often can become overly confident, confronting larger peers, or walking up to predatory creatures.

Robert C. Bolles (1970), a researcher at University of Washington, wanted to understand species-specific defense reactions and avoidance learning among animals, but found that the theories of avoidance learning and the tools that were used to measure this tendency were out of touch with the natural world.<ref>Template:Cite journal</ref> He theorized the species-specific defense reaction (SSDR).<ref>Template:Cite journal</ref> There are three forms of SSDRs: flight, fight (pseudo-aggression), or freeze. Even domesticated animals have SSDRs, and in those moments its seen that animals revert to atavistic standards and become "wild" again. Dr. Bolles states that responses are often dependent on the reinforcement of a safety signal, and not the aversive conditioned stimuli. This safety signal can be a source of feedback or even stimulus change. Intrinsic feedback or information coming from within, muscle twitches, increased heart rate, is seen to be more important in SSRDs than extrinsic feedback, stimuli that comes from the external environment. Dr. Bolles found that most creatures have some intrinsic set of fears, to help assure survival of the species. Rats will run away from any shocking event, and pigeons will flap their wings harder when threatened, the wing flapping in pigeons and the scattered running of rats are considered a species-specific defense reaction or behavior. Bolles believed that SSDR are conditioned through pavlovian conditioning, and not operant conditioning; SSDR arise from the association between the environmental stimuli and adverse events.<ref>{{#invoke:citation/CS1|citation |CitationClass=book }}</ref> Michael S. Fanselow conducted an experiment, to test some specific defense reactions, he observed that rats in two different shock situations responded differently, on based on instinct or defensive topography, rather than contextual information.<ref>Template:Cite journal</ref>

Species specific defense responses are created out of fear, and are essential for survival.<ref>Template:Cite journal</ref> Rats that lack the gene stathmin show no avoidance learning, or a lack of fear, and will often walk directly up to cats and be eaten.<ref>Template:Cite journal</ref> Animals use these SSDR to continue living, to help increase their chance of fitness, by surviving long enough to procreate. Humans and animals alike have created fear to know what should avoided, and this fear can be learned through association with others in the community, or learned through personal experience with a creature, species, or situations that should be avoided. SSDRs are an evolutionary adaptation that has been seen in many species throughout the world including rats, chimpanzees, prairie dogs, and even humans, an adaptation created to help individual creatures survive in a hostile world.

Neurocircuit of fear in mammals

Process of fear:

• The thalamus collects sensory data from the senses
• Sensory cortex receives data from thalamus and interprets it
• Sensory cortex organizes information for dissemination to hypothalamus (fight or flight), amygdala (fear), hippocampus (memory)

The brain structure that is the center of most neurobiological events associated with fear is the amygdala, located behind the pituitary gland. The amygdala is part of a circuitry of fear learning.<ref name=Olsson/> It is essential for proper adaptation to stress and specific modulation of emotional learning memory. In the presence of a threatening stimulus, the amygdala generates the secretion of hormones that influence fear and aggression.<ref>Best, Ben (2004). [http://www.benbest.com/science/anatmind/anatmd9.html The Amygdala and the Emotions]. benbest.com</ref> Once response to the stimulus in the form of fear or aggression commences, the amygdala may elicit the release of hormones into the body to put the person into a state of alertness, in which they are ready to move, run, fight, etc. This defensive response is generally referred to in physiology as the fight-or-flight response regulated by the hypothalamus, part of the limbic system.<ref>Gleitman, Henry; Fridlund, Alan J. and Reisberg, Daniel (2004). Psychology (6 ed.). W. W. Norton & Company. ISBN 0-393-97767-6.</ref> Once the person is in safe mode, meaning that there are no longer any potential threats surrounding them, the amygdala will send this information to the medial prefrontal cortex (mPFC) where it is stored for similar future situations, which is known as memory consolidation.<ref name=Travis/>

Some of the hormones involved during the state of fight-or-flight include epinephrine, norepinephrine and cortisol. Epinephrine regulates heart rate and metabolism as well as dilating blood vessels and air passages. Norepinephrine increases heart rate, blood flow to skeletal muscles and the release of glucose from energy stores.<ref>von Bohlen und Halbach, O; Dermietzel, R (2006). Neurotransmitters and neuromodulators: handbook of receptors and biological effects. Wiley-VCH. p. 125. ISBN 978-3-527-31307-5.</ref> Cortisol increases blood sugar, demarginalizes neutrophilic leukocytes, increases calcium and much more.<ref>Hoehn K, Marieb EN (2010). Human Anatomy & Physiology. San Francisco: Benjamin Cummings. ISBN 0-321-60261-7.</ref>

After a situation which incites fear occurs, the amygdala and hippocampus record the event through synaptic plasticity.<ref>Template:Cite pmid</ref> The stimulation to the hippocampus will cause the individual to remember many details surrounding the situation.<ref>Schacter, Daniel L.; Gilbert, Daniel T. and Wegner, Daniel M. (2011) Psychology Study Guide, Worth Publishers, ISBN 1429206152.</ref> Plasticity and memory formation in the amygdala are generated by activation of the neurons in the region. Experimental data supports the notion that synaptic plasticity of the neurons leading to the lateral amygdala occurs with fear conditioning.<ref>Template:Cite pmid</ref> In some cases, this forms permanent fear responses such as post-traumatic stress disorder (PTSD) or a phobia.<ref>American Psychiatric Association (1994). Diagnostic and statistical manual of mental disorders: DSM-IV. Washington, DC. ISBN 0-89042-061-0.</ref> MRI and fMRI scans have shown that the amygdala in individuals diagnosed with such disorders including bipolar or panic disorder is larger and wired for a higher level of fear.<ref>Template:Cite pmid</ref>

Pathogens can suppress amygdala activity. 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.<ref>Template:Cite pmid</ref> In a separate experiment, rats with lesions in the amygdala did not express fear or anxiety towards unwanted stimuli. These rats pulled on levers supplying food that sometimes sent out electrical shocks. While they learned to avoid pressing on them, they did not distance themselves from these shock-inducing levers.<ref>Template:Cite doi</ref>

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.<ref name=radua2010>Template:Cite pmid</ref> Interestingly, fearful eyes, brows and mouth seem to separately reproduce these brain responses.<ref name=radua2010 /> Scientist from Zurich studies show that the hormone oxytocin related to stress and sex reduces activity in your brain fear center.<ref>Fear not." Ski Mar.-Apr. 2009: 15. Gale Canada In Context. Web. 29 Sep. 2011</ref>

Fear pheromones and why fear can be contagious

In threatening situations insects, aquatic organisms, birds, reptiles, and mammals emit odorant substances, initially called alarm substances, which are chemical signals now called alarm pheromones ("Schreckstoff" in German). This is to defend themselves and at the same time to inform members of the same species of danger and leads to observable behavior change like freezing, defensive behavior, or dispersion depending on circumstances and species. For example, stressed rats release odorant cues that cause other rats to move away from the source of the signal. Pheromones are synthesized, emitted and perceived by all living organisms studied to date, with the exception of viruses and prions: i.e. in bacteria, prokaryotes, plants, plankton, parasites, insects, invertebrates and vertebrates (aquatic organisms, birds, reptiles, and mammals).

After the discovery of pheromones in 1959, alarm pheromones were first described in 1968 in ants <ref>Moser JC, Brownlee RC, Silverstein R. Alarm pheromones of the ant atta texana. J Insect Physiol. 1968 Apr;14(4):529-35.</ref> and earthworms,<ref>Ressler RH, Cialdini RB, Ghoca ML, Kleist SM. Alarm pheromone in the earthworm Lumbricus terrestris. Science. 1968 Aug 9;161(3841):597-9.</ref> and 4 years later also found in mammals, both mice and rats.<ref>Rottman SJ, Snowdon CT. Demonstration and analysis of an alarm pheromone in mice. J Comp Physiol Psychol. 1972 Dec;81(3):483-90.</ref> Over the next two decades identification and characterization of these pheromones proceeded in all manner of insects and sea animals, including fish, but it was not until 1990, that more insight into mammalian alarm pheromones was gleaned.

Early on, in 1985 a link between odors released by stressed rats and pain perception was discovered in that unstressed rats developed opioid mediated analgesia<ref>Fanselow MS. Odors released by stressed rats produce opioid analgesia in unstressed rats. Behav. Neurosci., 1985,99, 589–592</ref> In 1997 the "odor" was proven to be an alarm pheromone in honeybees who behaved similarly: Bees became less responsive to pain after they had been stimulated with isoamyl acetate, a chemical smelling of banana, and a component of bee alarm pheromone.<ref>Núñez J, Almeida L, Balderrama N, Giurfa M. Alarm pheromone induces stress analgesia via an opioid system in the honeybee. Physiol Behav. 1997 Dec 31;63(1):75-80.</ref> The experiment also showed that the bee’s fear-induced pain tolerance was mediated by an endorphine.

By using the forced swimming test in rats as a model of fear-induction, the first mammalian "alarm substance" was found.<ref>Abel EL, Bilitzke PJ. A possible alarm substance in the forced swimming test. Physiol Behav. 1990 Aug;48(2):233-9.</ref>

In 1991, this "alarm substance" was shown to fulfill criteria for pheromones: well-defined behavioral effect, species specificity, minimal influence of experience and control for nonspecific arousal. Rat activity testing with alarm pheromone and their preference/avoidance for odors from cylinders containing the pheromone showed, that the pheromone had very low volatility.<ref>Abel EL. Alarm substance emitted by rats in the forced-swim test is a low volatile pheromone. Physiol Behav. 1991 Oct;50(4):723-7.</ref>

In 1993 a connection between alarm chemosignals in mice and their immune response was found.<ref>Cocke R, Moynihan JA, Cohen N, Grota LJ, Ader R. Exposure to conspecific alarm chemosignals alters immune responses in BALB/c mice. Brain Behav Immun. 1993 Mar;7(1):36-46.</ref>

Pheromone production in mice was found to be associated with or mediated by the pituitary gland in 1994.<ref>Abel EL. The pituitary mediates production or release of an alarm chemosignal in rats. Horm Behav. 1994 Jun;28(2):139-45.</ref>

It was not until 2011 that a link between severe pain, neuroinflammation and alarm pheromones release in rats was found: real time RT-PCR analysis of rat brain tissues indicated that shocking the footpad of a rat increased its production of proinflammatory cytokines in deep brain structures, namely of IL-1β, heteronuclear Corticotropin-releasing hormone and c-fos mRNA expressions in both the paraventricular nucleus and the bed nucleus of the stria terminalis, and it increased stress hormone levels in plasma (corticosterone).<ref>Arakawa H, Arakawa K, Blandino P Jr, Deak T. The role of neuroinflammation in the release of aversive odor cues from footshock-stressed rats: Implications for the neural mechanism of alarm pheromones. Psychoneuroendocrinology. 2011 May;36(4):557-68.</ref>

In 2004, it was demonstrated that rats’ alarm pheromones had different effects on the “recipient“ rat (the rat perceiving the pheromone) depending which body region they were released from: Pheromone production from the face modified behavior in the recipient rat, e.g. caused sniffing or movement, whereas pheromone secreted from the rat's anal area induced autonomic nervous system stress responses, like an increase in core body temperature.<ref>Kiyokawa Y, Kikusui T, Takeuchi Y, Mori Y. Alarm pheromones with different functions are released from different regions of the body surface of male rats. Chem Senses. 2004 Jan;29(1):35-40.</ref> Further experiments showed that when a rat perceived alarm pheromones, it increased its defensive and risk assessment behavior.<ref>Kiyokawa Y, Shimozuru M, Kikusui T, Takeuchi Y, Mori Y. Alarm pheromone increases defensive and risk assessment behaviors in male rats. Physiol Behav. 2006 Feb 28;87(2):383-7.</ref> and its acoustic startle reflex was enhanced.

The neurocircuit for how rats perceive alarm pheromones was shown to be related to hypothalamus, brainstem, and amygdala, all of which are evolutionary ancient structures deep inside or in the case of the brainstem underneath the brain away from the cortex, and involved in the Fight-or-flight response, as is the case in humans.<ref>Kiyokawa Y, Kikusui T, Takeuchi Y, Mori Y. Mapping the neural circuit activated by alarm pheromone perception by c-Fos immunohistochemistry. Brain Res. 2005 May 10;1043(1-2):145-54.</ref>

Alarm pheromone-induced anxiety in rats has been used to evaluate the degree to which anxiolytics can alleviate anxiety in humans. For this the change in the acoutic startle reflex of rats with alarm pheromone-induced anxiety (i.e. reduction of defensiveness) has been measured. Pretreatment of rats with one of five anxiolytics used in clinical medicine was able to reduce their anxiety: namely midazolam, phenelzine (a nonselective monoamine oxidase (MAO) inhibitor), propranolol, a nonselective beta blocker, clonidine, an alpha 2 adrenergic agonist or CP-154,526, a corticotropin-releasing hormone antagonist.<ref>Inagaki H, Kiyokawa Y, Takeuchi Y, Mori Y. The alarm pheromone in male rats as a unique anxiety model: psychopharmacological evidence using anxiolytics. Pharmacol Biochem Behav. 2010 Feb;94(4):575-9.</ref>

Faulty development of odor discrimination impairs the perception of pheromones and pheromone-related behavior, like aggressive behavior and mating in male rats: The enzyme Mitogen-activated protein kinase 7 (MAPK7) has been implicated in regulating the development of the olfactory bulb and odor discrimination and it is highly expressed in developing rat brains, but absent in most regions of adult rat brains. conditional deletion of the MAPK7gene in mouse neural stem cells impairs several pheromone-mediated behaviors, including aggression and mating in male mice. These behavior impairments were not caused by a reduction in the level of testosterone, by physical immobility, by heightened fear or anxiety or by depression. Using mouse urine as a natural pheromone-containing solution, it has been shown that the impairment was associated with defective detection of related pheromones, and with changes in their inborn preference for pheromones related to sexual and reproductive activities.<ref>Zou J, Storm DR, Xia Z. Conditional deletion of ERK5 MAP kinase in the nervous system impairs pheromone information processing and pheromone-evoked behaviors. PLoS One. 2013 Oct 9;8(10):e76901. Template:DOI</ref>

Lastly, alleviation of an acute fear response because a friendly peer (or in biological language: an affiliative conspecific) tends and befriends is called "social buffering". The term is in analogy to the 1985 "buffering" hypothesis in psychology, where social support has been proven to mitigate the negative health effects of alarm pheromone mediated distress.<ref>Template:Cite journal</ref> The role of a "social pheromone" is suggested by the recent discovery that olfactory signals are responsible in mediating the "social buffering" in male rats.<ref>Takahashi Y, Kiyokawa Y, Kodama Y, Arata S, Takeuchi Y, Mori Y. Olfactory signals mediate social buffering of conditioned fear responses in male rats. Behav Brain Res. 2013 Mar 1;240:46-51.</ref> "Social buffering" was also observed to mitigate the conditioned fear responses of honeybees. A bee colony exposed to an environment of high threat of predation did not show increased aggression and aggressive-like gene expression patterns in individual bees, but decreased aggression. That the bees did not simply habituate to threats is suggested by the fact that the disturbed colonies also decreased their foraging.<ref>Rittschof CC, Robinson GE. Manipulation of colony environment modulates honey bee aggression and brain gene expression. Genes Brain Behav. 2013 Nov;12(8):802-11. Template:DOI</ref>

Biologists have proposed in 2012 that fear pheromones evolved as molecules of "keystone significance", a term coined in analogy to keystone species. Pheromones may determine species compositions, and affect rates of energy and material exchange in an ecological community. Thus pheromones generate structure in a trophic web and play critical roles in maintaining natural systems.<ref>Ferrer RP, Zimmer RK. Community ecology and the evolution of molecules of keystone significance. Biol Bull. 2012 Oct;223(2):167-77.</ref>

Fear pheromones in humans

Evidence of chemosensory alarm signals in humans has emerged slowly: Although alarm pheromones have not been physically isolated and their chemical structure has not been identified in man so far, there is evidence for their presence. Androstadienone, for example, a steroidal, endogenous odorant, is a pheromone candidate found in human sweat, axillary hair and plasma. The closely related compound androstenone is involved in communicating dominance, aggression or competition; sex hormone influences on androstenone perception in humans showed high testosterone level related to heightened androstenone sensitivity in men, a high testosterone level related to unhappiness in response to androstenone in men, and a high estradiol level related to disliking of androstenone in women.<ref>Lübke KT, Pause BM.Sex-hormone dependent perception of androstenone suggests its involvement in communicating competition and aggression. Physiol Behav. 2014 Jan 17;123:136-41. Template:DOI</ref>

A German study from 2006 showed when anxiety-induced versus exercise-induced human sweat from a dozen people was pooled and offered to seven study participants, of five able to olfactorily distinguish exercise-induced sweat from room air, three could also distinguish exercise-induced sweat from anxiety induced sweat. The acoustic startle reflex response to a sound when sensing anxiety sweat was larger than when sensing exercise-induced sweat, as measured by electromyograph analysis of the orbital muscle, which is responsible for the eyeblink component. This showed for the first time that fear chemosignals can modulate the startle reflex in humans without emotional mediation; fear chemosignals primed the recipient's "defensive behavior" prior to the subjects' conscious attention on the acoustic startle reflex level.<ref>Prehn A, Ohrt A, Sojka B, Ferstl R, Pause BM. Chemosensory anxiety signals augment the startle reflex in humans. Neurosci Lett. 2006 Feb 13;394(2):127-30.</ref>

In analogy to the social buffering of rats and honeybees in response to chemosignals, induction of empathy by smelling anxiety of another person has been found in humans.<ref>A. Prehn-Kristensen, C. Wiesner, T.O. Bergmann, S. Wolff, O. Jansen, H.M. Mehdorn et al. Induction of empathy by the smell of anxiety. PLoS One, 4 (2009), p. e5987</ref>

A study from 2013 provided brain imaging evidence that human responses to fear chemosignals may be gender-specific. Researchers collected alarm-induced sweat and exercise-induced sweat from donors extracted it, pooled it and presented it to 16 unrelated people undergoing functional brain MRI. While stress-induced sweat from males produced a comparably strong emotional response in both females and males, stress-induced sweat from females produced a markedly stronger arousal in women than in men. Statistical tests pinpointed this gender-specificity to the right amygdala and strongest in the superficial nuclei. Since no significant differences were found in the olfactory bulb, the response to female fear-induced signals is likely based on processing the meaning, i.e. on the emotional level, rather than the strength of chemosensory cues from each gender, i.e. the perceptual level.<ref>Radulescu AR, Mujica-Parodi LR. Human gender differences in the perception of conspecific alarm chemosensory cues. PLoS One. 2013 Jul 24;8(7):e68485.</ref>

An approach–avoidance task set up where volunteers seeing either an angry or a happy cartoon face on a computer screen pushed away or pulled toward them a joystick as fast as possible. Volunteers smelling anandrostadienone, masked with clove oil scent responded faster, especially to angry faces, than those smelling clove oil only, which was interpreted as anandrostadienone-related activation of the fear system.<ref>Frey MC, Weyers P, Pauli P, Mühlberger A. Androstadienone in motor reactions of men and women toward angry faces. Percept Mot Skills. 2012 Jun;114(3):807-25.</ref> A potential mechanism of action is, that androstadienone alters the "emotional face processing". Androstadienone is known to influence activity of the fusiform gyrus which is relevant for face recognition.

Fears in culture

Death

The fear of the end and its existence is in other words the fear of death. The fear of death ritualized the lives of our ancestors. These rituals were designed to reduce that fear; they helped collect the cultural ideas that we now have in the present. These rituals also helped preserve the cultural ideas. The results and methods of human existence had been changing at the same time that social formation was changing. One can say that the formation of communities happened because people lived in fear. The result of this fear forced people to unite to fight dangers together rather than fight alone.

Religion

Religions are filled with different fears that humans have had throughout many centuries. The fears aren't just metaphysical (including the problems of life and death) but are also moral. Death is seen as a boundary to another world. That world would always be different depending on how each individual lived their lives. The origins of this intangible fear are not found in the present world. In a sense we can assume that fear was a big influence on things such as morality.

There is another fear in the Bible that has a different meaning; the fear of God. Fear is used to express a Filial or a slavish passion. In believers the fear of god is "holy awe" or "reverence" of a particular god and the laws of its associated religion.

Manipulation

Fear may be politically and culturally manipulated to dissuade citizenry about the implementation of market-oriented policies, otherwise would be widely rejected. In contexts of disasters, nation-states manage the fear not only to provide their citizens with an explanation about the event or blaming some minorities, but also to adjust their previous beliefs. The manipulation of fear is done by means of symbolic instruments as terror movies and the administration ideologies that lead to nationalism. After a disaster, the fear is re-channeled in a climate of euphoria based on patriotism. The fear and evilness are inextricably intertwined.<ref>Template:Cite doi</ref>

Mirroring fears

Template:Unreferenced section Fear is found in mythology and folklore superstitions, and portrayed in books and movies. For example, many stories include characters who fear the antagonist of the plot. One of the important characteristics of historical and mythical heroes across cultures is to be fearless in the face of big and often lethal enemies.

Overcoming fear

Pharmaceutical

A drug treatment for fear conditioning and phobias via the amygdala is the use of glucocorticoids.<ref>Template:Cite doi</ref> In one study, glucocorticoid receptors in the central nucleus of the amygdala were disrupted in order to better understand the mechanisms of fear and fear conditioning. The glucocorticoid receptors were inhibited using lentiviral vectors containing Cre-recombinase injected into mice. Results showed that disruption of the glucocorticoid receptors prevented conditioned fear behavior. The mice were subjected to auditory cues which caused them to freeze normally. However, a reduction of freezing was observed in the mice that had inhibited glucocorticoid receptors.<ref>Template:Cite pmid</ref>

Psychology

Cognitive behavioral therapy has been successful in helping people overcome fear. Because fear is more complex than just forgetting or deleting memories, an active and successful approach involves people repeatedly confronting their fears. By confronting their fears—in a safe manner—a person can suppress the fear-triggering memory or stimulus. Known as ‘exposure therapy’, this practice can help cure up to 90% of people, with specific phobias.<ref name=Travis>Template:Cite doi</ref>

See also

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References

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Further reading

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External links

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• [http://www.nel.edu/23_2/NEL230202R01_Grammer.htm The Scent of Fear, a Research Study]
• [http://www.newadvent.org/cathen/06021a.htm Catholic Encyclopedia "Fear (from a Moral Standpoint)"]

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