Charles Bonnet Syndrome is an unusual neurological affliction that causes mentally healthy people to see things that aren’t actually there. It is usually associated with advancing age and is thought to affect between 10% – 40% of people. Hallucinations seen by those with Bonnet’s Syndrome range from colourful patterns and textures on walls, through out-of-place objects such as bottles and vases of flowers, to animals and faces and people. Perhaps one of the strangest things about the affliction is that the hallucinated items often appear to interact with the sufferer’s real environment. Charles Bonnet, who first described the disorder, observed it in his 89 year old grandfather who hallucinated birds, horse-drawn carriages, animals and perhaps most disturbingly of all, a man who would come into his bedroom and smoke a pipe in the evenings, and who was still there the next morning when the old man awoke…

The British Medical Journal reports the case of an 87 year old widower who had, for six weeks previous to his diagnosis with the condition, been seeing people and animals in his house, including bears and Highland cattle.

He knew that these visions were not real and they didn’t bother him much, but he thought he might be losing his mind. The visions lasted for minutes to hours, and the cattle used to stare at him while quietly munching away at the grass.

Bonnet’s Syndrome occurs mostly in people with some kind of macular degeneration, and the most likely explanation for what is going on is that the sufferer’s brain, lacking the visual information it is accustomed to receiving, feels obliged to conjure up something to fill the space. That it chooses to integrate that ‘something’ with the world of the patient is perhaps the weirdest part of the illness.

The lesson here, in case this post seems somewhat obtuse, is that you quite literally can’t always believe your eyes. The strangeness of Charles Bonnet Syndrome illustrates profoundly how deeply etched into our being is the ‘need’ to make sense of the world in some way when deprived of the proper data. In the case of the sufferer of Bonnet’s Syndrome, the brain makes an unmistakeable and totally misleading judgment call.

If you’d like to read more about Charles Bonnet Syndrome there’s a great piece on Damn Interesting.


Image (in part) by William Fox Talbot from Wikimedia Commons