What you need:
- A pencil
- A plastic comb with flexible bristles
- A friend
What to do:
1. Hold the comb horizontal, like it would rest on a flat surface.
2. With the comb held in one hand, place the index finger of your other hand over a section of bristles.
3. Ask your partner to hold the pencil vertically, so that it is perpendicular to the comb’s bristles.
4. Then ask him or her to run the pencil’s point horizontally over the bristles. Continue this action for a few seconds.
5. Swap positions with your friend so you can compare results.
What happens:
Instead of feeling the bristles move, your finger feels like there is a raised dot moving up and down the length of the comb.
Why?
This is a tactile illusion’. Tactile means related to the sensation of touch.
Our fingertips are among the most sensitive areas of our bodies. It means that we can fool them into feeling things quite easily!
When your fingertip rests on moving comb bristles, the skin on the finger gets alternately stretched and compressed. This sensation is so similar to the motion of running our finger back and forth over a raised surface (like a dot), that our brain interprets it that way.
Picture Credit : Google
