Random shivers
Also called: Shudder · "Someone walked over my grave"
A single brief shudder that runs down the spine or through the whole body when you are not cold. Many people report them. Nobody has counted them.
How common
Does this happen to you?
How it works
A shiver is a quick wave of small muscle contractions. When you are cold, the brain uses repeated shivering to make heat1. The random shudder uses the same muscles with no cold trigger. It comes once, runs down the back or through the whole body, and passes quickly.
Researchers use the term psychogenic shivers for chills at music, a film or an idea4. The random shudder has no such clear trigger. One untested idea is a brief burst from the sympathetic nervous system, the side of the nervous system that raises the heart rate and readies the body for action3. The same system triggers goosebumps, the piloerection reflex, thought by some to be a leftover from furred ancestors who fluffed their coat to trap heat or look bigger2. A random shiver may be that reflex firing with no real reason.
People report several triggers: a sudden thought, a creepy feeling, a change in room temperature too small to notice, moving after sitting still, and urinating. Shivers that come with a wave of emotion at music or a film are a separate thing, frisson, which has been studied properly.
How common it is
Nobody has counted them. There is no agreed definition and no standard survey question, so no epidemiologist has tried. The research term psychogenic shivers means chills at music or a film, not random shudders, so that work does not count these4. Forum threads and ordinary conversation suggest most people do, and that is the whole of the evidence. One question added to a large health or sleep survey would give the first real number.
Is it a problem?
No. A single random shiver is not known to be a sign of illness. It is different from the repeated shivering of a fever or of real cold, which has the clear job of making heat1. Mention it to a doctor only if the shivers come often, come with sweating or a fever, or arrive alongside other new symptoms, since that pattern points to a separate cause.
History and culture
An old English saying explains the shudder as “someone walking over my grave”. Many languages have a similar phrase. None of them are right, but they show the feeling has been noticed for a long time.
Sources and further material
- Wikipedia Shivering
- aeon.co Psychogenic shivers: why we get the chills when we aren't cold A researcher's summary of the term. It describes the feeling and gives no prevalence figure.
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Related oddities
Goosebumps
Tiny muscles at the base of most hairs pull the hair upright when you are cold, scared, or moved. In a furry animal this traps warm air or makes it look bigger. In a human the raised hair does almost nothing.
Pee shivers
A brief involuntary shudder during or just after urinating. Many people seem to get it, men more often than women. It is widely known and almost completely unstudied.
Frisson
A wave of chills up the back, sometimes with goosebumps, at a powerful moment in music, a film, or a speech. It is thought to come from the brain's reward system reacting to an expectation being met or broken.
Hypnic jerks
A sudden jolt of the arms, legs, or whole body just as you fall asleep, sometimes with a feeling of falling. Most people get them, and they are harmless.