ic nervous system and adrenal glands, including increased heart rate (tachycardia), increased breathing rate (tachypnea), tenseness or trembling of muscles, profuse sweating, and dryness of the mouth. Circulation from the rest of the body is directed to the areas where energy is needed most, either to protect oneself or to escape danger, also known as the "fight or flight" response. The sudden diversion of excess blood from the brain may also cause fainting, which may actually serve as an adaptive function in animals to protect them from predators.
Children experience fears with greater intensity than older people. Middle aged children as a group experience less fears than their older or younger siblings. There is a disagreement between researchers upon the degree to which fear is innate or a learned response. Pavlov’s research with conditioning led to various experiments through which animals were conditioned to fear certain stimuli which were previously neutral. However certain fears such as fear of pain, injury or loud noises are innate and appear to be universal.
Fear generally starts appearing in infants at 7 months of age. In newborns, fear is primarily reflexive. By instinct, they become afraid if there is sudden loss of support, extreme or unexpected sensory stimulus particularly with loud sounds. At about 6 to 9 months of age infants develop fear of masks, heights and strangers. Anxiety of separation typically appears at about 6 to 10 months of age and peaks between 18 and 24 months. Fear of being separated from the primary guardian is a universal reaction. The ability to understand constancy is not present in the young infant and it might believe that its mother might be gone forever if she is not currently present there. The peak that is observed at 18 to 24 months is probably because this is the age when most children enter day care or preschool.
At two years of age a child becomes more organized and develops a better sense of security. A two year