Skin & Hair · Involuntary response · Common
Goosebumps
Raised hair follicles in response to cold or emotion.
A lot is going on. Inside you.
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Something else to wonder about
Anatomical variation35Body sound12Body trick2Reflex22Rare ability1Involuntary response41Perception38
Bones & Joints · Common
Why joints crack
A single cracking sound during rapid joint movement.
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Eyes · Varies by individual
The stopped clock
After a rapid eye movement, the first new image seems visible for slightly longer.
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Nerves · Common
Hiccups
An involuntary spasm of the breathing muscles followed by closure of the glottis produces the characteristic hic.
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Try it now
A little moment of wonder. No equipment and no pressure to perform.
Faces in clouds
- Look at photos of clouds, tree bark, or everyday objects.
- Find a face-like arrangement and describe which two or three shapes create the impression.
Stop if uncomfortable. This is not a diagnostic test.
Why does this happen?3D from two images
- Hold one finger comfortably in front of you and look at a fixed object farther away.
- Close one eye and then the other without moving your head. The finger’s apparent shift shows the different viewing angles.
Stop if uncomfortable. This is not a diagnostic test.
Why does this happen?Aphantasia
- Think of a red apple without looking at a picture.
- Describe to yourself whether an inner image forms or whether you mainly know its properties. This is an observation, not a diagnostic test.
Stop if uncomfortable. This is not a diagnostic test.
Why does this happen?DiscoverExplore by body regionExpand or collapse all body regions.
Stranger still …
151 phenomena
Perception · CommonFloaters in vision
Threads or dots seem to move through the visual field, especially against a bright background.
Involuntary response · CommonAn earworm
A short passage of melody continues internally without a conscious decision.
Involuntary response · CommonWrinkled fingers in water
Finger skin wrinkles after prolonged contact with water.
Reflex · Varies by individualLight-induced sneezing
Bright light can trigger sneezing in some people.
Reflex · CommonSleep start
A brief muscle jerk can occur while falling asleep, sometimes with a feeling of falling.
Involuntary response · Varies by individualDermatographism
Light scratching pressure produces temporary raised lines.