A question from reader Josiah: "Do blind people see when they dream?Â I think there are two sides to the question, dealing with people who were born blind, and those who used to be able to see."
Whether visual imagery is present in the dreams of the blind has been pondered by scientists since the early 19th century. Josiah is right about that last part. People who are sighted, people who were born sighted but were blinded later in life, and people who were born blind all dream differently. As the Royal National Institute of the Blind in London puts it, "Dreams are experienced in the same way as life is lived." (Some people over 55 occasionally dream in black and white, while younger people who grew up with color television tend to dream only in color.1) How much visual imagery someone has experienced in their waking life—if they've experienced it at all—affects how much visual imagery is in their dreams.
A series of questionnaire and interview studies conducted in the 1970s2 led to four generalizations about the dreams of the blind:
1. People born blind, and who never experienced visual imagery in waking life, have no visual images in their dreams.
2. People who became blind before the age of five rarely experience visual imagery in their dreams.
3. People who became blind between the ages of five and seven sometimes retain some visual imagery and experience it in their dreams.
4. Most people who became blind after the age of seven continue to experience at least some visual imagery in their dreams, but the clarity and frequency of the imagery is often reduced with time.
Several studies in sleep laboratories, in which blind participants were woken up during REM sleep for the collection of dream reports, reported similar results.
A more recent study3 analyzed a sample of 372 dreams from 15 blind adults—some born blind, and others who went blind later in life. Again, the study found that people blind since birth or very early childhood experienced no visual imagery, and people blinded later in life did retain some visual imagery from their sighted waking lives and experienced it while dreaming.
One participant in the study, though, reported visual imagery inconsistent with the trends described in previous findings. Participant 13, a 24-year-old man blinded at age four, reported that he was able to see objects "clearly" or "plainly" during the dream, so it is possible that some people who became blind before the age of five can experience visual imagery in dreams.
The study also expanded upon the previous research and revealed two interesting things:
1. While less than one percent of sighted participants surveyed in two previous studies reported experiencing gustatory, olfactory, or tactual sensations in dreams, all but three of the blind participants in this study reported experiencing them. One participant, who has been blind since birth, reported that 48 percent of the sensations in his dreams were auditory and the other 52 percent were a mix of taste, smell and touch sensations.
2. Sixty percent of the blind men's dreams that involved locomotion or transportation, and 61% of the blind women's, had at least one incident of "dreamer-involved misfortune" (the norms for sighted men and women are 31 percent and 28 percent, respectively), which the researchers hypothesize is a continuation of the waking-life concerns that the blind have about getting from place to place.
1 Murzyn E. (2008). Do we only dream in colour? A comparison of reported dream colour in younger and older adults with different experiences of black and white media. Consciousness and cognition. Dec;17(4):1228-37.
2 Kirtley, D. (1975). The psychology of blindness. Chicago: Nelson-Hall.
3 Hurovitz, C., Dunn, S., Domhoff, G. W., & Fiss, H. (1999). The dreams of blind men and women: A replication and extension of previous findings. Dreaming. 9:183-193.
[Image courtesy of Christophe Moustier.]