Found this unique channel that discusses all things foot and tickling related. Here are a couple of intersting vids (remove the space):
The sociological impact of tickling across different cultures (video essay)
you tube.com/watch?v=XcSIvUtFzeU
Understanding how long it takes to get used to tickling
you tube.com/watch?v=pex_7rsiSvY
Video Essay: The Surprising Benefits of Tickle Therapy
you tube.com/watch?v=6hWwQuD7zws
The sociological impact of tickling across different cultures (video essay)
you tube.com/watch?v=XcSIvUtFzeU
Understanding how long it takes to get used to tickling
you tube.com/watch?v=pex_7rsiSvY
Video Essay: The Surprising Benefits of Tickle Therapy
you tube.com/watch?v=6hWwQuD7zws