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Why We Dream: Biological Theory Roundup

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We've all had strange dreams: as a kid I was not in the least frightened by the Count Chocula character while awake, but I suffered through many a nightmare about him, his fangs dripping chocolate blood as he stalked me, Bela Lugosi-style, through the eerily empty halls of my school. God knows why. Other dreams make even less sense: I'm packing for a trip when there's a knock at the door. It's Fedex. For some reason, supreme court nominee Sandra Sotomayor has overnighted me a kitten.

So why does the brain produce this narrative junk? We still don't know why for certain, but the last few decades have produced a number of interesting evolutionary theories that move beyond old-hat Jungian archetypes or Freudian "wish fulfillment," and Scientific American's Jesse Bering recently laid out the Darwinian contenders.

Brain conditioning

If your brain went completely dark all night, the theory goes, it would begin to lose function just as rarely-used muscles will atrophy.

Several researchers, including the psychophysiologist Fred Snyder, argued that the adaptive purpose of dreaming may therefore be primarily to stimulate the brain or to keep it "in shape" during prolonged periods of inactivity. Later research offered support for this general idea. For example, specific categories of neurotransmitters were shown to be highly active during this period, while others seemingly "rested."

In other words, as psychologist Steven Pinker puts it, "Dreaming might be a kind of screen saver in which it doesn't really matter what the content is as long as certain parts of the brain are active."

External vigilance

Most dreams are notably lacking in olfactory and auditory content, and one theory holds that that's because if they were, the dreamer would be particularly susceptible to real-world threats like fire or noisy predators.

Being a "light sleeper" in relation to these other sensory domains had adaptive benefits, and since we're in the dark anyway and our eyes are closed, there's less of a risk in hallucinating in our secret visual worlds while our brains are being recharged.

Threat Simulation

This theory holds that dreams function as practice run-throughs for dangerous situations that may occur in the real world; they're drills. (Of course, this theory doesn't explain my kitten-in-the-mail dream; what was that preparing me for?)

"By giving rise to a full-scale hallucinatory world of subjective experience during sleep, the dream production mechanism provides an ideal and safe environment for such sustained practice by selecting threatening waking events and simulating them repeatedly in various combinations." What we should see in contemporary dreams, argues Revonsuo, are "threat scripts" depicting primitive themes of danger that would likely have been relevant in the ancestral environment, such as being chased, falling and so on.

Dreaming as problem solving

According to Harvard University psychologist Deirdre Barrett, "sleeping on it" really works in terms of real-world problem solving, and may actually be the evolutionary purpose of dreaming (even if those dreams don't always make sense to us.) In other words --

-- dreamscapes provided our ancestors (and therefore us) with a sort of creative canvas for solving real-world problems. In support of this, Barrett describes the work of Stanford University psychologist William Dement, who in the early 1970s instructed hundreds of undergraduate students to work on a set of challenging brainteasers before bedtime, so that they'd fall asleep with the problems still on their mind.

What do you think?

Painting by Jamal Vrno.

You can follow my weird dreamlife via Twitter.

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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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