Fear is a vital survival response to threats and is also an important component of mammalian behavioral defense systems. Ivan Pavlov (1920s) introduced the concept of classical conditioning. Classical conditioning can be used to learn various emotions, including fear; this is called a conditioned emotional response (Carlson, 2010, p. 369). In this essay, Pavlovian fear conditioning (indicated) and contextual fear conditioning will be discussed, and then the neural mechanisms underlying fear conditioning will be evaluated using various studies in animals and humans. In Pavlovian fear conditioning, an emotionally neutral conditioned stimulus (CS) is presented in competition with an aversive unconditioned stimulus (US). After one or more pairings, the CS is able to elicit responses that would naturally occur when danger is detected. Responses are innate and occur automatically upon the appearance of appropriate stimuli. Some of the responses that usually occur are behavioral (freezing), autonomic (change in blood pressure or heart rate), and endocrine (secretion of stress hormones) mechanisms {Aggleton, 2000, p. 292}. One of the classic examples of fear conditioning is the experiment carried out on little Albert by Watson and Rayner (1920). Little Albert was an infant (11 months old) conditioned to fear white rats. At first, when he was exposed to the white rat, little Albert would approach it and play with it. After a while, when little Albert tried to touch the rat, a loud noise (US) was created which surprised little Albert and made him cry (unconditioned response –UR). This pairing was repeated several times. Later, when the rat (CS) was introduced to little Alber again...... middle of paper ...... uh. Some of these responses include: freezing, changes in blood pressure or heart rate, or the release of stress-related hormones. The neural mechanisms underlying fear conditioning have been extensively analyzed in recent years. The amygdala and the hippocampus are two major elements of fear conditioning. The amygdala deals with the formation of associations, while the hippocampus deals with the contextual conditioning of fear. These findings typically come from lesion, neuroimaging, and behavioral studies. However, other crucial questions are also being researched, such as whether the amygdala is the storage location for fear memory or what is the precise amygdala circuit that mediates fear conditioning. Advances in exploring underlying neural mechanisms may help improve learning and memory, and also help understand the basis of fear and anxiety disorders..