An illusion is a distortion of the senses, revealing how the brain normally organizes and interprets sensory stimulation. While illusions distort reality, they are generally shared by most people. Illusions may occur with more of the human senses than vision, but visual illusions, optical illusions, are the most well known and understood. For example, in the left figure, although square A is exactly the same shade of grey as Square B, we perceive A is darker than B.





In the same manner, we experience haptic illusions. There are examples of haptic illusion.
(1) Phantom limb: 
-  the sensation that an amputated or missing limb (even an organ, like the appendix) is still attached to the body and is moving appropriately with other body parts
(2) Thermal grill illusion 
- sensory illusion originally demonstrated in 1896 by T. Thunberg. The illusion is created by an interlaced grill of warm (e.g., 40°C) and cool (20°C) bars. When someone presses a hand against the grill, he or she experiences the illusion of burning heat.
(3) Cutaneous Rabbit illusion(cutaneous saltation)
 -  tactile illusion evoked by tapping two separate regions of the skin. Many experiments demonstrating the effect have been carried out on the forearm. A rapid sequence of taps delivered first near the wrist, and then near the elbow creates the sensation of sequential taps hopping up the arm from the wrist towards the elbow, although no physical stimulus was applied between the two actual stimulus locations.
(4) crossed index and middle fingers
- When the crossed index and middle fingers are run along the bridge of the nose with one finger on each side, resulting in the perception of two separate noses.
(5) Hole and bump confusion
- Hole and bump confusion in the perception through active touch found by Robles-De-La-Torre and Hayward. Using paradoxical stimuli, for example combining the force cues of a bump with the geometry of a hole, they found that subjects perceived a bump. Conversely, when combining the force cues of a hole with the geometry of a bump, subjects typically perceived a hole.


HOME ASSGNEMNT: Hunt up any ‘Haptic illusion phenomenon’ and discuss its Applicability!
- Each student has to prepare 10 minutes presentation.