Graphesthesia: In Greek, Grapha means writing and aisthesis means perception. In common parlance, Graphesthesia usually refers to a person’s ability to recognize writing (usually single letters) on the skin (usually tested on the palm).
During medical or neurological exams this is sometimes tested in order to test for certain neurological conditions. An examiner (nurse or doctor) writes single numbers or simple letters on the skin with something dull (back of pen, pen light, tongue depressor, etc). Testing positive is considered normal, testing negative (not understanding the letters) is considered non-normal and patient may be referred to a specialist.
Printed reference: Physical Examination and Health Assessment written by Carolyn Jarvis. (printed by Saunders/elsevier). ISBN-13: 978-0-7216-9773-4 or ISBN-10: 0-7216-9773-9.
Online references: Medical library University of Utah: http://library.med.utah.edu/neurologicexam/html/sensory_normal.html
Biology Online.org: http://www.biology-online.org/dictionary/Graphesthesia