The web address given below doesn't work. This one seems to:

http://web.mit.edu/~tkonkle/www/BiasedVert.html

The article on the Haptic illusion follows:

Scientists create touch-based illusion

Anyone who has seen an optical illusion can recall the quirky moment
when you
realize that the image being perceived is different from objective
reality. Now,
a team of scientists from MIT, Harvard and McGill has designed a new
illusion
involving the sense of touch, which is helping to glean new insights
into
perception and how different senses-such as touch and sight-work
together.