Illusions —- Tactile – Optical – Auditory – Olfactory – Taste

The term illusion refers to a specific form of sensory distortion. Unlike a hallucination, which is a distortion in the absence of a stimulus, an illusion describes a misinterpretation of a true sensation. While illusions distort reality, they are common in most people. The most common illusions are:

  1. Visual (optical illusion)
  2. Auditory
  3. Tactile (touch)
  4. Olfactory (smell)
  5. Taste

Visual illusions (optical illusions), are the most well known and understood. The emphasis on visual illusions occurs because vision often overpowers the other senses. One example is watching a ventriloquist. We perceive the voice is coming from the dummy since we are able to see the dummy mouth the words.

Mimes create illusions that are created by physical means. The mime creates an illusion of acting upon or being acted upon by an unseen object. Well known examples include “walls”, “climbing stairs”, “leaning”, “descending ladders”, “pulling and pushing” etc.     An optical illusion is always characterized by seeing a real image but the perceived images are deceptive or misleading.


Move your head forward and backward. As your head moves closer to your monitor and then back away from your monitor, the circles will appear to be spinning. But are they really spinning? Absolutely NOT!


The horizontal grey bar is the same shade throughout


Is it a face or a vase?

An auditory illusion is an illusion of hearing, the sound equivalent of an optical illusion: the listener hears either sounds which are not present in the stimulus, or “impossible” sounds. For example, hearing voices regardless of the environment would be a hallucination, whereas hearing voices in the sound of running water (or other auditory source) would be an illusion.

An example of tactile illusions is a phantom limb. A phantom limb is 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. Approximately 50 to 80% of individuals with an amputation experience phantom sensations in their amputated limb, and the majority of the sensations are painful. Phantom sensations may also occur after the removal of body parts other than the limbs, e.g. after amputation of the breast, extraction of a tooth (phantom tooth pain) or removal of an eye (phantom eye syndrome). The missing limb often feels shorter and may feel as if it is in a distorted and painful position. Occasionally, the pain can be made worse by stress, anxiety and weather changes. Phantom limb pain is usually intermittent. The frequency and intensity of attacks usually decline with time

Illusions can occur with the other senses including that of taste and smell.

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11 Responses

  1. I hope that at some point you will talk about the difference between illusions and delusions, and how it applies in LBD. This was very enlightening!

    • Hi Sherry………….yes, I’ll be doing that. I plan to do a post on delusions and one on halluciantions as well.


  2. This was very interesting. My grandmother sometimes sees things that aren’t there. Mostly people. Thanks for letting me know the difference. I also am interested in the difference between an illusion and a delusion.

    I look forward to that post!

  3. If the circles don’t move is that an illusion too? I’m puzzled.

    • Hi Cindy………..illusions are based upon an external stimulus. In this case it is the circle with the dots. In reality, nothing about the circle is moving and neither are the dots. If one perceives anything about the circle or its parts moving, then it is an illusion. The circle itself doesn’t have to move. I hope this helps…….


  4. I have heard from a number of people that hallucinations frequently involve little boys. In the case of my husband, Gordon that was true. He say lot os lttle boys in the bedroom or the living room. Sometimes they filled the house. I would love to know your thoughts on the content of hallucinations.

    Thanks David, Hope

  5. […] with the terms, illusions, delusions and hallucinations. I’ve discussed the topic of illusions here. Today, I will begin to discuss the topic of delusions. Since it is fairly long, I will divide it […]

  6. […] with the terms, illusions, delusions and hallucinations. I’ve discussed the topic of illusions here. Part 1 is an overview of delusions. Today, I will discuss the types of delusions. Part 3 will give […]

  7. […] with the terms, illusions, delusions and hallucinations. I’ve discussed the topic of illusions here. Part 1 is an overview of delusions. Part 2 covers the types of delusions. Today, I will discuss […]

  8. My husband has Alzheimers with Lewy bodies. He believes there are a lot of people living in our house, doing the housework and gardening, (I wish) and they are all very nice, but sometimes they hide things and sometimes they try to get him to give them access to our share Bank account.

  9. please explain the Olfactory and taste illusion also…

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