Here is a more recent Scientific American 60 Second Science on the misperception of unseen hand size. Subjects thought their unseen hands were "about two thirds wider and one third shorter than they really were". The "neuroscientific explanation" invokes the mental representation of the hand.
But, C&S claim, "Note that neither Gibson nor Skinnerians claim that the brain is not importantly involved in cognition; rather they claim that psychologists can do all their explanatory work without referring to the brain." (Chemero & Silberstein, 2008, p.4).
So, what is the Gibsonian or Skinnerian explanation? I guess there must be one. I know that Shaun Gallagher has done a lot of work on this kind of body image/body schema issue.