Things that happen to you, sometimes frighteningly, that are benign or very common.
Showing 30 oddities.
Involuntary entries are things that happen to you, not things you do. Nobody decides to have a hypnic jerk while falling asleep, or a bout of déjà vu, and nobody can stop one once it starts.
This kind differs from reflex by its trigger. A reflex has one clear, repeatable cause, like a tap on a tendon. An involuntary event often has no obvious trigger, or a trigger too vague to pin down, like the sudden thought behind call of the void.
The boundary case is something like migraine aura, which follows a rough pattern but not a fixed trigger the way a knee-jerk reflex does. What keeps it in this kind, rather than reflex, is that timing and cause stay unpredictable, even though the pattern of the event itself is well known.
Results narrow the list below as you type.
A pleasant tingling that starts on the scalp and moves down the neck and spine, set off by whispering, tapping, soft sounds, or gentle personal attention. Not everyone gets it. A large online community is built around it.
Small visible twitches in the eyelid, calf, thumb, or arm that come and go with no weakness. One survey found them in about 70% of healthy clinicians. They are very rarely a sign of nerve disease.
A short, intense spinning feeling set off by turning over in bed or tipping your head back. Tiny crystals in the inner ear have drifted into the wrong place. It is the most common cause of vertigo and it is very treatable.
A short, sharp headache in the forehead a few seconds after cold food or drink touches the roof of the mouth. It usually passes in under a minute.
A brief feeling like a small electric shock inside the head, often set off by moving the eyes. It is most common when stopping or lowering an antidepressant. It is unpleasant, but usually not a problem.
A sudden, brief thought of jumping when you stand somewhere high, with no wish to do it. About half of people get it. It is probably the brain's safety system being misread, not a hidden wish.
A strong feeling that you have lived the present moment before, even though you know you have not. About two in three people get it. It peaks between the ages of 15 and 25.
The world suddenly seems flat, distant, or like a film (derealization), or you feel like you are watching yourself from outside (depersonalization). Many people have a brief episode at some point, usually under stress.
A loud bang, crash, or explosion heard inside the head while falling asleep or waking up. Nothing actually happens, there is no pain, and it is harmless.
Small grey threads, dots, or cobwebs that drift across your vision and dart away when you look at them. They are shadows of tiny clumps inside the eye. They are common and usually harmless.
Tiny pale yellow or white bumps, 1 to 3 mm across, on the edge of the lips or inside the cheeks. They are ordinary oil glands in a place without hair. Most adults have them.
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.
Vivid images, sounds, or touches that appear while you are falling asleep or waking up. A face, a voice saying your name, a hand on your shoulder. They may be dream fragments arriving early or late, and they are usually normal.
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.
A familiar word, face or place suddenly feels strange, as if you are meeting it for the first time. It is the opposite of déjà vu, and researchers think it is rarer. In lab studies, more than half of people felt a common word turn strange after copying it about 30 times.
A shimmering zigzag or C-shaped patch of light that grows across your vision over 5 to 60 minutes and then fades. It can come before a migraine headache or, in some people, with no headache at all.
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.
You feel your phone buzz in your pocket, check it, and nothing happened. Most phone users get this. The cause is not known. The brain may misread ordinary sensations as a buzz.
The flashes, rings, and patterns of light you see when you rub or press your closed eyes, or after a knock on the head. Pressure on the eye makes the retina fire without any light.
The prickling, buzzing feeling in a limb after you sit on it or lean on it. It happens when blood returns to a squeezed nerve and its sensory fibres briefly fire on their own.
A sudden, sharp, stabbing pain near the heart that lasts seconds to a few minutes and gets worse when you breathe in. Doctors count it among the most common causes of chest pain in children and teenagers, and it is harmless.
A sudden, cramping pain deep in the rectum that lasts seconds to minutes and then goes away completely. It has no known cause, and it is harmless.
Fingertips and toes wrinkle after several minutes in water. This is not just the skin soaking up water. It is the nervous system shrinking the fingertip on purpose, and the wrinkles may improve grip when wet.
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.
Stroke a rubber hand and a person's hidden real hand at the same time, and within a minute or two the brain adopts the rubber hand as its own. It shows that your sense of your body is built moment by moment from sight and touch.
You stand up fast, your vision goes grey or sparkly, and your head feels light for a few seconds. Blood has briefly pooled in your legs. It passes on its own.
You wake up, or start to fall asleep, and cannot move or speak for a few seconds to minutes. Sometimes a threatening presence seems to be in the room. It is the normal paralysis of dreaming sleep running a little late.
A ringing, hissing, buzzing, or roaring sound with no source outside your head. Between 10% and 15% of people have it. It is mostly the hearing system filling in for damaged or tired inner-ear cells.
Small white or yellow lumps that form in the folds of the tonsils and sometimes come out when you cough. They smell bad and feel like something is stuck in the throat. They are usually harmless.
Tiny flickering dots across the whole field of vision, like static on an old TV, present with eyes open or closed. About 2% of people have it. The eyes are fine. The visual part of the brain is over-active.