Perception and hallucinations

What are perceptions and hallucinations?

Learn more about vision and perception and dementia,

Some people with dementia may encounter problems with their sight – in some cases, this includes having hallucinations. This page looks at some of the difficulties and mistakes this can cause, and suggests ways of providing support for the person. Understanding the problems they may face and giving appropriate help, support and reassurance can help people living with dementia to feel safe. This is especially important at a time when the way they perceive the world around them may be changing.

Vision and perception

The complicated process of seeing involves many different stages. Information comes through our eyes to the brain, where it is interpreted in relation to our expectations (of what will be seen), other senses, thoughts and memories. We then become aware of what has been seen (what is ‘perceived’). Problems that involve both vision and perception can be referred to as ‘visuoperceptual difficulties’. As there are many different stages involved in the seeing process, various different types and combinations of mistakes can occur. Common mistakes include:

  • misperceptions – the person sees one thing as something else. For example, mistaking a coat hanging up for a person, or a blue coloured floor as water
  • misidentifications – damage to specific parts of the brain can lead to problems identifying specific objects and people. For example, mistaking a son for a husband or brother.

It is easy to see how these mistakes may lead to the person with dementia saying or doing things that do not make sense to others. However, what they are experiencing is not a problem with thinking (it is not based on incorrect reasoning or ‘delusional thinking’). Instead, it is the result of damage to the visual system.