In psychiatry, subjective premonitory symptoms preceding an epileptic convulsionand in some cases an acute migraine attack or other approaching disorder. Sensations of all types (psychic, sensory, visceral, motor) may be experienced: peculiar odors, strange tastes, colored lights, feelings of numbness, crawling sensations, stomach discomfort, weird sounds, muffled voices, deja vu, feelings of unreality, a compulsive desire to run. Each patient experiences his own typical aura and may learn to use it as a warning of an impending seizure. In some cases there is time to prepare for the attack; in others, the convulsion follows immediately. The term aura is also used in parapsychology and psychical research to denote alleged emanations from the body. These emanations are believed to be visible to others who are sensitive to such phenomena. Some people claim to see halos surrounding the head or entire body of certain individuals, and even rank them in a spiritual hierarchy. A violet aura is thought to indicate a high degree of spirituality, a yellow aura a low degree.