Fear. Fear is a feeling induced by perceived danger or threat that occurs in certain types of organisms, which causes a change in metabolic and organ functions and ultimately a change in behavior, such as fleeing, hiding, or freezing from perceived traumatic events. Fear in human beings may occur in response to a certain stimulus occurring in the present, or in anticipation or expectation of a future threat perceived as a risk to body or life. The fear response arises from the perception of danger leading to confrontation with or escape from/avoiding the threat, which in extreme cases of fear 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 acute stress reaction, anger, angst, anxiety, fright, horror, joy, panic, and sadness. Fear is closely related to, but should be distinguished from, the emotion anxiety, which occurs as the result of threats that are perceived to be uncontrollable or unavoidable. The fear response serves survival by engendering appropriate behavioral responses, so it has been preserved throughout evolution. Sociological and organizational research also suggests that individuals' fears are not solely dependent on their nature but are also shaped by their social relations and culture, which guide their understanding of when and how much fear to feel. 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, heart rate, vasoconstriction of the peripheral blood vessels leading to blushing and sanskadania of the central vessels, increasing muscle tension including the muscles attached to each hair follicle to contract and causing goose bumps, or more clinically, piloerection, sweating, increased blood glucose, increased serum calcium, increase in white blood cells called neutrophilic leukocytes, alertness leading to sleep disturbance and butterflies in the stomach. This primitive mechanism may help an organism survive by either running away or fighting the danger. With the series of physiological changes, the consciousness realizes an emotion of fear. 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, enclosed spaces, or water. There are studies looking at areas of the brain that are affected in relation to fear. When looking at these areas, 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.