Graphesthesia

Graphesthesia is the ability to recognize writing on the skin purely by the sensation of touch. Its names derives from Greek grapha ("writing") and aisthesis ("perception").

During medical or neurological examination this is sometimes tested in order to test for certain neurological conditions. An examiner writes single numbers or simple letters on the skin (usually the palm) with something dull like the back of pen, pen light, tongue depressor, etc. Testing positive is considered normal, testing negative (not understanding the letters) is considered non-normal and the patient may be referred to a specialist.