New World monkeys like the cotton-top tamarin, in stressed mice and rats, and in frightened cats. In humans In humans, goose bumps can even extend to piloerection as a reaction to hearing nails scratch on a chalkboard, listening to awe-inspiring music, or feeling or remembering strong and positive emotions (e.g., after winning a sports event), or while watching a horror film. Some can deliberately evoke goose bumps in themselves without any external trigger. Such people tend to have the ability to increase their heart-rate and describe the event as a chill from the base of their skull down the body, that causes the increase in heart-rate and concurrent goose bumps on the skin especially the forearms which varies in duration. Further research is needed to discover more on such people. Goose bumps are accompanied by a specific physiological response pattern that is thought to indicate the emotional state of being moved. In humans, goose bumps are strongest on the forearms, but also occur on the legs, neck, and other areas of the skin that have hair. In some people, they even occur in the face or on the head. Piloerection is also a classic symptom of some diseases, such as temporal lobe epilepsy, some brain tumors, and autonomic hyperreflexia. Goose bumps can also be caused by withdrawal from opiates such as heroin. A skin condition that mimics goose bumps in appearance is keratosis pilaris. Causes Extreme temperatures Goose bumps can be experienced in the presence of flash-cold temperatures, for example being in a cold environment, and the skin being able to re-balance its surface temperature quickly. The stimulus of cold surroundings causes the tiny muscles (arrector pili muscle) attached to each hair follicle to contract. This contraction causes the hair strands to stand straight, the purpose of which is to aid in quicker drying via evaporation of water clinging to the hair which is moved upward and away from the skin. Intense emotion People often say they feel their "hair standing on end" when they are frightened or in awe. In an extremely stressful situation, the body can employ the "fight or flight" response. As the body prepares itself for either fighting or running, the sympathetic nervous system floods the blood with adrenaline (epinephrine), a hormone that speeds up heart-rate, metabolism, and body temperature in the presence of extreme stress. Then the sympathetic nervous system also causes the piloerection reflex,