What do the blind dream?

Sleep 2 sliderOur image of the world is a very personal one – it both relies on our senses and is shaped by them. It is impossible to know whether everyone else experiences the world the same way we do; and it makes it very hard to imagine what it’s like when one of these senses is missing.

Dreams are different. They are bizarre nocturnal adventures that barely resemble the real world. When we dream, our sensory organs stop relaying information to our brain – yet, we are seeing, hearing and smelling things from our mind. So can someone who’s never actually seen suddenly see in their dream – or do they not dream?

A group of researchers at the University of Copenhagen answered that very question just last year. Their study compared dream reports of individuals who were either normal-sighted, blind from birth, or blind after the age of one year. Every day for four weeks, all volunteers answered a battery of questions about the dreams they remembered.

They found that the longer someone had been blind, the less they saw; those born blind saw nothing at all. However, the “blind” dreams weren’t just blank. They were just as rich with experiences and feelings as a seeing person’s; there were the same number of social encounters, the same kinds of emotions, the same Dali-esque bizarreness – except that their experiences were made through physical touch, smell and hearing instead of vision. And most dream experiences were auditory – much like how the blind experience day-to-day life.

Besides the lack of vision, there was another remarkable difference: the blind reported nightmares a staggering 25% of the time compared to just 6% in the sighted. Nightmares are thought to be simulations of potential threatening situations (unlikely as some of them may seem), and the blind volunteers’ dreams were very much in line with this: they dreamt of falling down sewers, losing their guide dogs and being hit by cars – all of which are very real threats to the blind, who – in our very visually-biased society – are constantly at risk.

Generally, humans are very visual creatures, so we do tend to “lose sight” of the other senses. The truth is that vision just happens to have won the evolutionary lottery amongst human senses: in bats, hearing is the dominant sense (hence the expression “being blind as a bat”). Bats use echolocation to sense the position and shape of the object they’re chasing or about crash into. The image they generate from sound in their brain may even be in colour. Similarly, many other animals use smell to get a grasp of their surroundings. For we sighted people, it’s hard to imagine not depending on vision, but it is possible – as are non-visual dreams.

 

Isabel Hutchison

 

Amani, M. et al., (2014). The sensory construction of dreams and nightmare frequency in congenitally blind and late blind individuals. Sleep Medicine, 15 (5): 586-595.

Richard Dawkins. (July 2013). “Seeing” with the Ears. Can bats hear in colour? richarddawkins.net. https://richarddawkins.net/2013/07/seeing-with-the-ears-can-bats-hear-in-colour-with-polish-translation/. (Accessed 18 February 2015).

 

Photo Credit: donnierayjones via Compfight cc

Article by Isabel Hutchison

February 18, 2015

Isabel is currently working on a Ph.D. in the Cognitive Neuroscience of Sleep (which, ironically, involves not getting very much sleep at all). Besides doing science and writing about it (check out her sleep science blog here), Isabel loves music, dancing , travelling and art.


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