// HACKER NEWS — CYBERSECURITY
Bodily Oddities
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. About 70% of healthy people get them. They are not 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 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 not dangerous.
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.
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.
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.
Some earlobes hang free and others join the head directly. Textbooks taught this as one gene, but a 2017 study found at least 49 genetic regions involved, and the two shapes blend into each other.
The uvula, the dangling flap at the back of the throat, is split into two lobes, in about 1 to 2% of people. On its own it is harmless, but in a baby it can be a clue to a hidden cleft of the palate.