Have you ever seen something that wasn't really there? Heard someone call your name in an empty house? Sensed someone following you and turned around to find nothing? Hallucinations don't belong wholly to the insane. Much more commonly, they are linked to sensory deprivation, intoxication, illness, or injury. People with migraines may see shimmering arcs of light or tiny, Lilliputian figures of animals and people. People with failing eyesight, paradoxically, may become immersed in a hallucinator