Diego Kaski poses an interesting question

"The eye of man hath not heard, the ear of man hath not seen, man's hand is not able to taste, his tongue to conceive, nor his heart to report, what my dream was."
Shakespeare, A Midsummer Night's Dream

Despite recent advances in the understanding of sleep, dreams continue to bewitch us with their unfathomed mysteries. Dreaming occurs during paradoxical sleep, a stage in which people's eyes move rapidly under the eyelids, and is therefore also known as rapid eye movement sleep. As we know from our own dreams, what we dream reflects our waking life experiences, which are mostly visual in nature. Are the content of visually impaired people's dreams related to their lack of vision? Do they have visual images while dreaming? Indeed, how do visually impaired people dream?

The content of dreams

Dreaming can be considered to be a passive event, a phenomenon that we experience but do not consciously control. When dreaming it can be said that we are mere onlookers of an unfolding drama. Nevertheless, some people claim to have "lucid" dreams - where they are aware of dreaming and are able to control the events of the dream. The content of a dream resembles what we experience in everyday life when we are awake. Usually, dreams are visual and mostly in colour (61%, but this proportion increases with longer dreams). Auditory and visual imageries are the most common sensations present in dreams (found in 76% and 100% of dreams respectively).¹ External sounds can be incorporated, but on the odd occasion that dreamers speak of entirely auditory experiences, they tend to claim that they were not asleep at all. Other sensations, such as taste and smell, are not as common.

Most dream settings are familiar, and most of the people that appear in dreams are known to the dreamer (apparently, celebrities crop up only rarely). So, if the content of dreams are a reflection of waking life, it follows that the dream content of people with physical conditions, such as visual handicap, must be related to their physical condition, in this case the absence of vision. Therefore, do visually impaired people who are afflicted from birth lack visual imagery and rapid eye movements in their dreams?

Dream content in the visually impaired

People who are visually impaired from birth (congenitally visually impaired) seem to lack visual imagery and rapid eye movements in their dreams. 2 3 The majority of the people who became visually impaired before they were aged 5 or 7 will have no visual dreams, but if sight is lost after the age of 7 visual imagery is retained in dreams into adulthood, with rapid eye movements present during sleep.^2,4,5 With few exceptions, when visual handicap occurs between the critical ages of 5 and 7, visual imagery remains for varying periods of time, even in adulthood, and tends to get worse over time. Although it is thought that rapid eye movements are essential for visual dreams,^2,6 it seems that many congenitally visually impaired people show eye movements during rapid eye movement sleep periods despite having no visual imagery.

With the exception of the absence of vision, the dreams of those who became visually impaired before the age of 5 are no different in most aspects to those of the sighted, containing perceptions of sounds, touch, taste, smell, and temperature sensations (in decreasing order).^2,7 As depicted in the example of a dream of a congenitally visually impaired person, heard speeches and conversations are prominent in visually impaired people's dreams: "I was going up to heaven and St Peter barred me at the gates, telling me to go down below. I argued with him, feeling I was being treated unjustly, until he said: 'All your friends are down there'; whereupon I said, 'If that's the case it's fine,' and I went down below."³ It may seem surprising that taste and smell form such a minor part of dreams, given their importance to visually impaired people.

Visual imagery and dreams

For most sighted people dream images are predominantly visual in nature. Visual imagery, however, is not the only means by which we can represent our surroundings. Just as when they are awake, visually impaired people can be conscious of their surrounding space while dreaming, through sensations other than touch. For example, a congenitally visually impaired person, dreaming that he or she is in a room, may be aware of the size and shape of the room, without describing, touching, or walking around in it. It is interesting that although visually impaired people may have different sensory experiences than sighted people they may express what they perceive using the same visual terminology as the sighted. The dream reports of visually impaired subjects can therefore be difficult to interpret.

For the sighted, the visual component of imagery is its most noticeable feature, so it is difficult for those of us with sight to consider images and imagery without using visual metaphor or analogy. Yet much of the work that has been carried out on dreams of the visually impaired underlines the need for a broader definition of imagery - one that is not so strongly bound to the visual processing system.

1. Snyder F. The phenomenology of dreaming, 1970. Cited in: Ellman SJ, Antrobus JS, eds. The mind in sleep: psy- chology and psychophysiology. New York:Wiley, 1991.
2. Berger RJ, Olley P, Oswald I. The EEG, eye-movements and dreams of the blind. Q J Exp Psychol 1962;14:183-6.
3. Blank HR. Dreams of the blind. Psychoanal Q 1958;27:158-74.
4. Jastrow J. The dreams of the blind. New Princeton Review 1880;5:19-34.
5. Heermann G. Beobachtungen und Betrachtungen uber die Traume der Blinden. Ein Beitrag zur Physiologie und Psychologie der Sinne Monatschrift fur Medzin. Augen-heikkunde und Chirurgie 1838;I:116-80. Cited in Blank HR. Dreams of the blind. Psychoanal Q 1958;27:158-74.
6. Offencrantz W, Wolpert E. Clinical studies of sequential dreams. Arch Gen Psychiatry 1963;8:497-508.
7. Amadeo M, Gomez E. Eye movements, attention, and dreaming in subjects with lifelong blindness. Canadian Psychiatric Association Journal 1966;11:501-7.