New Scientist has got a nice feature online where they explain seven touch illusions you can try yourself, with the explanations for how they’re tricking your brain.
My favourite is probably the most simple, the ‘Aristotle illusion':
One of the oldest tactile illusions is the Aristotle illusion. It is easy to perform. Cross your fingers, then touch a small spherical object such as a dried pea, and it feels like you are touching two peas. This also works if you touch your nose.
This is an example of what is called “perceptual disjunction”. It arises because your brain has failed to take into account that you have crossed your fingers. Because the pea (or nose) touches the outside of both fingers at the same time – something that rarely happens – your brain interprets it as two separate objects.
It’s a fantastic little collection and it follows on from NewSci’s recent collection of five auditory you can check out online.
Link to NewSci seven tactile illusions.