Eyes Perception
Afterimages
An image that stays in your vision after the thing you looked at is gone. Bright things leave a same-colour copy for a moment. Long stares leave a copy in opposite colours.
Everyone
Brain
Things the brain does on its own: memory glitches, sleep events, perception errors, unusual wiring.
49 oddities. 35 have this as their primary region.
Brain Perception
Alice in Wonderland syndrome
Objects, body parts, or the whole room suddenly look far too big, far too small, or far away. It mostly happens to children, often during a fever or infection, and it passes on its own. In adults it is usually linked to migraine.
6–7% of teenagers (size distortion)
Brain Trick
Ambidexterity
Using both hands equally well for every task. Fewer than 1% of people are truly ambidextrous. Most people who say they are ambidextrous are mixed-handed: right hand for some jobs, left for others.
Under 1%
Brain Involuntary
ASMR
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.
Unclear; estimates 20–70%
Ears Involuntary
BPPV
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.
About 2.4% of people, lifetime
Brain Involuntary
Brain zaps
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 not dangerous.
Common when stopping antidepressants
Brain Involuntary
Call of the void
A sudden, brief thought of jumping when you stand somewhere high, or of swerving while driving, with no wish to do it. About half of people get it. It is the brain's safety system being misread, not a hidden wish.
43–60% of people
Brain Perception
Charles Bonnet syndrome
People who lose a lot of their sight often start to see things that are not there: patterns, faces, small people in costume, whole landscapes. They know the images are not real. It is caused by the eyes, not the mind.
10–40% of people with serious sight loss
Brain Perception
Chronostasis
Glance at a clock and the second hand seems to freeze for a moment before it moves. The brain hides your eye movement and stretches the first thing you see to cover the gap.
Everyone
Eyes Perception
Closed-eye hallucinations
Close your eyes and you do not see nothing. You see speckle, drifting colour, and, as you fall asleep, moving patterns and even scenes. Everyone has them. Almost nobody talks about them.
Everyone
Brain Reflex
Contagious yawning
Seeing, hearing, or even reading about a yawn makes about half of adults yawn. The effect appears in early childhood, is linked to empathy, and crosses over to dogs.
About 50–60% of adults
Nerves Reflex
Cutaneous rabbit illusion
A few quick taps at the wrist followed by taps at the elbow feel like a small animal hopping up the arm. The brain fills in taps between the two spots that never happened.
Works on most people tested
Brain Involuntary
Déjà vu
A strong feeling that you have lived the present moment before, even though you know you have not. Almost everyone gets it. It peaks between the ages of 15 and 25.
60–97% of people
Brain Involuntary
Derealization and depersonalization
The world suddenly seems flat, distant, or like a film (derealization), or you feel like you are watching yourself from outside (depersonalization). Most people have a brief episode at some point, usually under stress.
50–75% of people, at least once
Brain Rare ability
Eidetic memory
Some children can keep a detailed picture of an image in view for a short time after it is taken away. The ability fades by the teenage years. A true photographic memory in adults has never been confirmed.
2–10% of children aged 6–12
Brain Involuntary
Exploding head syndrome
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.
10–37% of people, lifetime
Brain Involuntary
Frisson
Goosebumps and a wave of chills down the back at a powerful moment in music, a film, or a speech. About half of people get it regularly. It comes from the brain's reward system reacting to an expectation being met or broken.
About 50% of people, regularly
Brain Perception
Ganzfeld effect
Fill your whole field of view with a featureless colour and, within minutes, your brain starts inventing shapes, lights, and scenes. Two halved ping-pong balls and a lamp are enough to do it at home.
Most people who try it
Brain Perception
Geometric nightmares
A kind of dream, usually during fever in childhood, filled with huge or tiny shapes, infinite space, crushing pressure, and dread. The name comes from an online forum, not a medical text, but each piece of it is well known to neuroscience.
Unknown. Common in children with fever
Heart Trick
Heart rate control
Slowing or speeding up your own heartbeat on purpose, using breath, attention, or training. Most people can shift it a little within minutes. A few trained people shift it a lot.
Most people, a little
Brain Rare ability
Highly superior autobiographical memory
A few dozen people worldwide can recall what happened on almost any date of their adult lives, in detail and without effort. Their memory for other things, such as lists or numbers, is ordinary.
About 62 documented cases
Brain Rare ability
Human echolocation
Some blind people find their way by making sharp tongue clicks and listening to the echoes. Brain scans show the echoes are processed in the visual cortex. Sighted people can learn a basic version in a few weeks.
Rare, mostly among blind people
Brain Rare ability
Human magnetoreception
Birds, turtles, and many other animals sense Earth's magnetic field. Whether humans do is unsettled. A 2019 experiment found brain-wave changes in response to a rotating field, but nobody has shown a conscious magnetic sense.
Unknown
Brain Involuntary
Hypnagogic hallucinations
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 are dream fragments arriving early or late, and they are normal.
About 25–37% of people
Brain Involuntary
Hypnic jerks
A sudden jolt of the arms, legs, or whole body just as you fall asleep, often with a feeling of falling. Most people get them, and they are harmless.
60–70% of people
Eyes Trick
Independent eye movement
Moving one eye while the other stays still, or moving the two eyes in different directions. Very rare in humans. Chameleons do it all day.
Very rare; no formal count
Brain Perception
Meditation body dissolution
During long, still meditation the brain loses track of the arms and the edges of the body. Hands can feel close to the shoulders and far away at the same time. Flotation tanks produce the same effect. It is common, harmless, and well studied.
Common in long-term meditators
Brain Involuntary
Migraine aura
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.
About 3% of people
Brain Rare ability
Mirror-touch synesthesia
About 1 in 60 people feel a touch on their own body when they watch someone else being touched. The brain system that mirrors other people's actions appears to be turned up too high.
About 1.6% of people
Brain Perception
Motion aftereffect
Watch something move in one direction for half a minute, then look at something still. The still thing appears to drift the opposite way for a few seconds.
Everyone
Brain Sound
Musical ear syndrome
Some people with hearing loss hear clear, complete music that no one is playing. The brain replays stored songs to fill the silence. The person knows the music is not real.
About 2–3% of people with profound hearing loss
Eyes Perception
Palinopsia
An image that keeps appearing after the thing you saw is gone. Brief trails behind moving objects are common and harmless. Copies that persist or return minutes later need a doctor.
Brief trailing is common. Persistent forms are rare.
Brain Rare ability
Perfect pitch
About 1 in 10,000 people can name or sing any musical note without hearing a reference note first. It runs in families and is far more common in people who started music lessons very young.
About 1 in 10,000 people
Brain Involuntary
Phantom phone vibrations
You feel your phone buzz in your pocket, check it, and nothing happened. Most phone users get this. It is a normal learning effect in the brain, not a fault.
68–89% of phone users
Eyes Involuntary
Phosphenes
The flashes, rings, and patterns of light you see when you rub or press your closed eyes, or after a knock on the head. The retina fires from pressure instead of light.
Everyone
Nerves Perception
Pinocchio illusion
Vibrate the biceps tendon while a person touches their own nose with their eyes closed, and their nose feels as if it is growing. It shows how the brain works out where the body parts are.
Most people, in lab conditions
Brain Perception
Prisoner's cinema
After hours or days in darkness, people start to see light shows: colours, geometric patterns, and sometimes figures or scenes. Prisoners, miners, polar explorers, and meditators all report it.
Up to 77% of people after 4 days blindfolded
Brain Involuntary
Rubber hand illusion
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.
70–80% of participants
Brain Rare ability
Savant syndrome
A very small number of people with a developmental disability or brain injury have one extraordinary skill, such as instant calendar calculation, drawing a city from memory, or playing a piece of music after one hearing.
About 1 in 1,000,000 people
Brain Rare ability
Short sleeper syndrome
A small number of people need only 4 to 6 hours of sleep a night, wake without an alarm, and feel fine. Several gene variants that cause it have been found. Most people who sleep that little are simply sleep-deprived.
Well under 1% of people
Brain Involuntary
Sleep paralysis
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.
8–30% of people, lifetime
Brain Perception
Strange-face illusion
Stare at your own face in a mirror in dim light for a few minutes and it starts to distort. Most people see their features warp. Some see a stranger, an animal, or a monster.
66% see their face distort
Brain Perception
Synesthesia
In some people, one sense triggers another. Letters have colours, sounds have shapes, or days of the week sit in fixed places in space. The pairings are automatic and stay the same for life.
About 4% of people
Eyes Perception
The blind spot
Each eye has a hole in its field of view where the optic nerve leaves the retina. You never notice it, because the brain paints over the gap with whatever surrounds it.
Everyone
Ears Sound
The sound of silence
In a room that absorbs almost all sound, you hear your heartbeat, your blood, your breath, and a high ringing from your own inner ear. True silence is not possible for a living person.
Everyone, given a quiet enough room
Ears Involuntary
Tinnitus
A ringing, hissing, buzzing, or roaring sound with no source outside your head. Between 15% and 20% of people have it. It is mostly the hearing system filling in for damaged or tired inner-ear cells.
About 15–20% of people
Eyes Perception
Troxler effect
When you hold your gaze on one point, things in the edge of your vision fade out and disappear. The brain stops reporting anything that does not change.
Everyone
Brain Involuntary
Visual snow
Tiny flickering dots across the whole field of vision, like static on an old TV, present with eyes open or closed. About 2–3% of people have it. The eyes are fine. The visual part of the brain is over-active.
About 2–3% of people
Eyes Trick
Voluntary pupil control
Changing the size of your pupils by will alone, without imagining a light or doing sums. Only a handful of cases are documented. Indirect control by thinking hard is possible for almost everyone.
A handful of documented cases