Fear

phobic SG

Fear is an unpleasant feeling of perceived risk or danger, real or not. Fear also can be described as a feeling of extreme dislike to some conditions/objects, such as: fear of darkness, fear of ghosts, etc. It is one of the basic emotions.

Fear may underlie some phenomena of behavior modification, although these phenomena can be explained without adducing fear as a factor in them. Furthermore, application of aversive stimuli is also often ineffective in producing change in the behaviour intended to be changed. Fearing objects or contexts can be learned; in animals this is being studied as fear conditioning, which depends on the emotional circuitry of the brain.

Fear inside a person has different degrees and varies from one person to another (see also phobia). If not properly handled, fear can lead to social problems. People who experience intense fear have been known to commit irrational and/or dangerous acts.

Some philosophers have considered fear to be a useless emotion with uniformly bad consequences; other thinkers note the usefulness of fear as a warning of bad situations.

http://en.wikipedia.org/wiki/Fear

phobic SG

Fear conditioning is a form of learning in which fear is associated with a particular neutral context (e.g., a room) or neutral stimulus (e.g., a tone). This can be done by pairing the neutral stimulus with a shock. Eventually, the neutral stimulus alone brings the animal to the state of fear.

After fear conditioning, fear can be measured in several different ways. Humans can verbally express or rank their level of fear, but this is not a reliable measure and cannot be used with animal subjects. Freezing, a period of watchful immobility, is one of the most common measures of fear in animals. Fear potentiated startle is another measure of fear and refers to the augmetation of the startle reflex by fearful stimulus. Changes in heart rate and breathing can also be used to measure the fear of an animal or person subjected to fear conditioning. In most studies, all of these measures would be taken before and after fear condtioning.

Fear conditioning is thought to depend upon the amygdala. Deactivating the amygdala with drugs that block neurotransmitters prevents both the learning and expression of fear. Other forms of classical conditioning depend on the cerebellum and the hippocampus.