There are two types of responses that women demonstrate when their soles are stroked. One type clenches their feet in order to get relief from the tickling. The other type curls their toes back when their soles are stroked. I much prefer the type that curls ther toes back to expose the full glory of their soles. This affords an unobstructed tickling surface and they seem to be saying, 'Have at it!'.