Many people theorize that the arch tends to be a very ticklish spot because it doesn't touch the ground (or insole of a shoe) by virtue of it's raised up shape. Unless of course the person has fallen arches in which case this would be an exception. But the rationale behind the theory is that areas of skin which do not recieve regular or frequent stimulation would tend to be more sensitive to the touch because they are not used to being touched all the time. A lot of foot ticklers like really high arches for this reason. You'll notice that because the the heel,ball of the foot, and the pads of the toes all touch the ground when we walk, the skin there tends to be tougher and in many cases less ticklish. However, tickle a soft wrinkly arch or the stems of the toes and watch the foot squirm wonderfully.
Just my 2 cents. 🙂
- DFT
