Parapsychologists have historically claimed that the shape and color of the corona around a human fingertip can diagnose illnesses. For example, a jagged or "broken" corona is said to indicate stress or organ dysfunction. While the corona does change based on the subject's physiology, it is not a mystical force. For instance, a person with sweaty hands (hyperhidrosis) due to nervousness will produce a large, fuzzy corona because the moisture conducts electricity more easily. A person with dehydrated skin will produce a thin, spiky corona. While these physiological states correlate with health, the mechanism is electrical, not metaphysical.