What if you have thick (old or mechanical worker) skin or thin (young or office worker) skin, dry or moist, and the ambient temperature? The difference could be over 20 degrees. Will your pinky burn faster than your index? On the side of the head or jammed down next to the plug? Hardly scientific Jim, A thermometer works better, with less pain and repeatable results. Tuners don't use body parts for testing, they use calibrated instruments. Do you use your hand for a hammer? Or your eye as a vernier? Select the tool for the job and the results will be accurate. A burnt finger is anyones guess to good tuneup..