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Do Blind People See Things in Their Dreams?

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A question from reader Josiah: "Do blind people see when they dream? 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.]

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Scientists Think They Know What Causes Trypophobia
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Picture a boat hull covered with barnacles, a dried lotus seed pod, milk bubbles on a latte, or a honeycomb. Images of these objects are harmless—unless you're one of the millions of people suffering from trypophobia. Then they're likely to induce intense disgust, nausea, and fear, and make your skin crawl.

Coined fairly recently, the term trypophobia describes the fear of clusters of holes. The phobia isn’t recognized by the Diagnostic and Statistical Manual of Mental Disorders, but its visibility on the internet suggests that for many, it’s very real. Now, scientists in the UK think they've pinpointed the evolutionary mechanism behind the reaction.

Tom Kupfer of the University of Kent and An T. D. Le of the University of Essex shared their findings in the journal Cognition and Emotion. According to their research, trypophobia evolved as a way to avoid infectious disease. Thousands of years ago, if you saw a person covered in boils or a body covered in flies, a natural aversion to the sight would have helped you avoid catching whatever they had.

But being disgusted by skin riddled with pathogens or parasites alone doesn't mean you're trypophobic; after all, keeping your distance from potential infection is smart. But trypophobia seems to misplace that reaction, as the authors write: "Trypophobia may be an exaggerated and overgeneralized version of this normally adaptive response."

Lotus pod.
Lotus seed pods are a common trigger of trypophobia.

This explanation is not entirely new, but until now little research has been done into whether it's accurate. To test their hypothesis, the scientists recruited 376 self-described trypophobes from online forums, and another 304 college students who didn't claim to have the affliction. Both groups were shown two sets of images: The first depicted clusters of circle-shaped marks on animals and human body parts (the "disease-relevant cluster images"); the second showed clusters of holes on inanimate objects like bricks and flower pods ("disease-irrelevant cluster images"). While both groups reported feeling repulsed by the first collection of photographs, only the trypophobes felt the same about the pictures that had nothing to do with infection.

Another takeaway from the study is that trypophobia is more related to sensations of disgust than fear. This sets it apart from more common phobias like arachnophobia (fear of spiders) or acrophobia (fear of heights). And you don't have to be trypophobic to be disgusted by a video of Suriname toadlets being born through holes in their mother's back. We can all be grossed out by that.

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Researchers Say You’re Exercising More Than You Think
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They say a journey of a thousand miles starts with a single step. If the thought of a thousand-mile journey makes you tired, we've got some great news for you: You've probably already completed one.* A new study published in the journal Health Psychology [PDF] finds that people underestimate the amount of exercise they're getting—and that this underestimation could be harmful.

Psychologists at Stanford University pulled data on 61,141 American adults from two huge studies conducted in the 1990s and the early 2000s: the National Health Interview Survey and the National Health and Nutrition Examination Survey. Participants answered questionnaires about their lifestyles, health, and exercise habits, and some wore accelerometers to track their movement. Everybody was asked one key question: "Would you say that you are physically more active, less active, or about as active as other persons your age?"

The researchers then tapped into the National Death Index through 2011 to find out which of the participants were still alive 10 to 20 years later.

Combining these three studies yielded two interesting facts. First, that many participants believed themselves to be less active than they actually were. Second, and more surprisingly, they found that people who rated themselves as "less active" were more likely to die—even when their actual activity rates told a different story. The reverse was also true: People who overestimated their exercise had lower mortality rates.

There are many reasons this could be the case. Depression and other mental illnesses can certainly influence both our self-perception and our overall health. The researchers attempted to control for this variable by checking participants' stress levels and asking if they'd seen a mental health professional in the last year. But not everybody who needs help can get it, and many people could have slipped through the cracks.

Paper authors Octavia Zahrt and Alia Crum have a different hypothesis. They say our beliefs about exercise could actually affect our risk of death. "Placebo effects are very robust in medicine," Crum said in a statement. "It is only logical to expect that they would play a role in shaping the benefits of behavioral health as well."

The data suggest that our ideas about exercise and exercise itself are two very different things. If all your friends are marathoners and mountain climbers, you might feel like a sloth—even if you regularly spend your lunch hour in yoga class.

Crum and Zahrt say we could all benefit from relaxing our definition of "exercise."

"Many people think that the only healthy physical activity is vigorous exercise in a gym or on a track," Zahrt told Mental Floss in an email. "They underestimate the importance of just walking to the store, taking the stairs, cleaning the house, or carrying the kids."
 
*The average American takes about 5000 steps per day, or roughly 2.5 miles. At that pace, it would take just a little over a year to walk 1000 miles.

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