Why you should care
For those who can’t see, dreams reflect their waking lives — meaning they hear, taste, touch and smell much more than sighted individuals.
Years ago, Tom Lane dreamed that someone was calling out to him from a van parked outside his Los Angeles home. He recognized the driver right away: his idol, Jimi Hendrix. The musician wanted to give him one of his guitars. So Lane climbed inside and started jamming on one. But it “had a strange vibe.” Although unplugged, it still wailed and buzzed with electricity.
Sometimes people think we can see like sighted people in our dreams.
For most people, dreams are intensely visual. Lane’s dream, though, was anything but; the 60-year-old computer instructor has been blind almost since birth. He can perceive some light — but has never seen color or shapes. He recognized Hendrix from the sound of his voice and knew the guitar was a Fender Stratocaster from its sleek, contoured shape.
Most people’s dreams are primarily visual; out of the five senses, we tend to use sight and sound most. But according to a study published by researchers from the University of Copenhagen and Glostrup Hospital in Denmark in Sleep Medicine in May 2014, blind people’s dreams contain a broader array of sensory inputs, including sounds and tastes — all the senses other than sight that they use to navigate their world.
Among congenitally blind volunteers, 93% heard, 26% tasted and 40% smelled in at least one dream.
The study’s 50 adult volunteers included 11 who were blind from birth (or congenitally blind), 14 who became blind after age 1, and 25 sighted controls. During the next four weeks, they completed a questionnaire about their dreams, if they had one, with a computer installed with software that read the questions aloud to them, and conversely, transcribed their verbal responses. The questions asked about the senses involved — in other words, whether they saw, tasted, smelled or heard anything. They also asked about emotional content, such as whether the dreamer felt happy or scared; the thematic content, like how realistic or bizarre the dream was; and whether or not it was a nightmare.
As expected, all the sighted participants reported seeing in at least one dream, while none of the congenitally blind participants reported any. And among those who lost their sight after age 1, those who lived with blindness the longest reported the fewest visual impressions.
“Sometimes people think we can see like sighted people in our dreams,” said Kellie Walders, an assisted technology instructor in L.A. who has been blind since shortly after birth, but has some light perception. “But I can only see the amount that I see in real life because that’s all I know.”
Blind participants experienced other senses more intensely than sighted controls. About 86 percent of blind participants reported hearing in at least one dream, but only 64 percent of controls did. About 18 percent of the blind participants tasted versus 7 percent of controls. Twenty-eight percent of the blind participants smelled in at least one dream, compared with 15 percent of controls. And a whopping 70 percent of the blind participants said that they experienced touch, versus 45 percent of controls. Separating out congenitally blind volunteers, 93 percent heard, 26 percent tasted and 40 percent smelled in at least one dream. Sixty-seven percent experienced touch. Lane once dreamed about walking into a woodshop, which he recognized from its sharp turpentine odor. Walders often dreams about making coffee, which she can both smell and taste.
But blind volunteers’ dreams were just as bizarre as those of their sighted counterparts. Both groups’ dreams also featured similar amounts of successes, failures and social interactions, and the same frequency and intensity of each emotion.
Nightmares more often plagued the blind, though. About 25 percent of congenitally blind participants reported that at least one of their dreams was a nightmare, versus 7 percent of the later-onset blind group and 6 percent of sighted participants. At this point, it’s not clear why. But an explanation might lie in one theory that nightmares allow us to safely practice detecting and avoiding threats. Sure enough, the congenitally blind participants’ nightmares reflected the real-world threats they often face, like being run over by a car. Walders once dreamed about losing her guide dog. “I felt panicked and kept calling and calling her,” she recalled. “She’s like my baby.” For both blind and sighted individuals, their dreams tend to relate to their experiences while awake, including desires, fears and daily routines, the researchers wrote.
They noticed similar trends in a study published in Neural Plasticity earlier this year. Fourteen congenitally blind and 14 sighted individuals sniffed sweat samples from volunteers who had watched film clips that evoked amusement, fear, disgust or sexual arousal. Congenitally blind subjects did better than controls at identifying fear and disgust. “If you don’t have any visual input, you have to get information from other sources,” says Ron Kupers, a faculty member at the University of Copenhagen’s Department of Neuroscience and Pharmacology, who led both the Sleep Medicine and Neural Plasticity studies.
Now, Kupers is investigating which aspects of visual memory – the ability to visualize color or faces, for example – fade first in late-onset blind individuals. Another ongoing study will compare the sleep patterns of sighted and congenitally blind individuals, some with their eyes removed. Kupers expects blind individuals who lack so-called non-image forming retinal ganglion cells, crucial to controlling sleep-wake patterns, to experience sleep disturbances, in turn linked to a slew of health problems, from obesity to Alzheimer’s disease. As the population steadily grows older, the findings could also apply to people suffering from age-related eye diseases, like macular degeneration. Even in our sleep, we’re not so different after all.