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Illusion - Tactile illusions

What is illusion?

(Oxford Dictationary)

It is the instance of a wrong or misinterpreted perception of a sensory experience.

* Sensation & Perception

- Optical (visual) illusions

- Auditory (hearing) illusions

- Tactile (touching) illusions

Tactile illusions

Tactile illusions are illusions that distort the sense of touch.

- Active touch

- Induced passively

Why study illusion?

(Hayward, 2008)

Today's experiments

- Active touch

e.g. Aristotle illusion

- Induced passively

e.g. Distance misjudgment

-Practical Use

-Understand the

sensory mechanism

-Valid and challenge a theory

Aristotle illusion

  • One of the oldest tactile illusion
  • First described by Aristotle in the essay On Dreams
  • Tactile diplopia (diplesthesia) on the human fingers (Benedetti, 1985)

Experiment

  • Cross the middle and index fingers
  • Close your eyes
  • Partner puts 1/2 stick(s) in between your crossed fingers
  • Guess how many sticks are there

Explanation

When the fingers are beyond the limit of the voluntary movement, sensation of the stimulus is referred back to the limiting position, where achieves with voluntary muscular effort

Explanation

Summary

(Benedetti, 1985)

  • Neuromuscular apparatus activities
  • Spatial location of the stimulus is perceived in the natural limit position

(Pasquinelli, 2005)

Distance Misjudgment

  • Proposed by Weber (1978)
  • Related to the different acuity level of different skin region

Experiment

- Illusion is the distortion of reality

due to the misinterpretation

- Aristotle illusion:

Neuromuscular apparatus limitations

- Distance misjudgment: receptor

  • Relax, and give your hand to your partner
  • Close your eyes
  • Your partner will put the paperclip on different regions of your hand
  • Guess if the distance of the paperclip is changed

Explanation

Taylor-Clarke, Jacobsen & Haggard (2004)

Reference

  • (2008-01-01). Aristotle's illusion. In . : . Retrieved 8 Oct. 2013, from http://www.oxfordreference.com/view/10.1093/oi/authority.20110803095423799.
  • Benedetti, F. (1985). Tactile Diplopia (diplesthesia) on the human fingers. Journals of Experimental Psychology: Human Perception and Performance, 11(4), 517-525.
  • Pasquinelli, E. (2005). Aristotle's illusion [PPT document]. Retrieved from : elenapasquinelli.free.fr/links/Pasquinelli_2005_Lyon.ppt‎
  • Taylor-Clarke, M., Jacobsen, P., Haggard, P. (2004). Keeping the world a constant size: object constancy in human touch. Nat Neurosci, 7(3), 219–220.
  • Weber, E.H. (1978). The Sense of Touch. London: Academic.
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