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Why We Dream: Biological Theory Roundup

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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Live Smarter
How to Choose the Best Watermelon
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Buying a watermelon is an experience one can grow to resent. The 92 percent moisture content of Citrullus lanatus means you're basically buying a giant ball of water. On the plus side, they're delicious and packed with enough vitamin C and D to keep you from getting scurvy.

But how to select the best of the batch? Food blogger Emma Christensen over at kitchn recently offered some advice, and it involves a little weight-training. When you examine watermelons in the produce section of your local grocery, you want to look for the heaviest one for its size. The denser the fruit, the more juice it has. That's when it's at its most ripe.

Next, check the underside of the watermelon for the "splotch." That's the yellow patch the watermelon develops by resting on the ground. If it's a creamy yellow, it's also a good indicator of being ripe.

Finally, give the underside a little smack—not aggressive enough to draw attention from grocery workers, but enough so that you can determine whether the watermelon sounds hollow. If it does, that's good. If it sounds dull, like you're hitting a solid brick of material, it's overripe; put the watermelon down and slowly back away from it.

If you're not confident in your watermelon evaluation abilities, there's another option: Local farmers markets typically have only choice product available, so any watermelon you pick up is likely to be a winner. You can also ask the merchant to pick one out for you. Pay attention to what he's doing and then try to emulate it the next time you're forced to choose your own produce.

[h/t: kitchn]

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Health
The CDC Makes It Official: Public Pools Are Disgusting
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Every summer, warm weather sends people across the country looking for a cool refuge in public pools, hotel pools, spas, and other water-based destinations. Before you take the plunge, you may want to heed the advice of the Centers for Disease Control and Prevention (CDC). Jumping into a publicly-populated pool could be like bathing in someone else’s diarrhea, as Men’s Health reports.

The health agency revealed its findings in their Mortality and Morbidity Report, which explains why pools are ground zero for bacteria. Between 2000 and 2014, the CDC traced 493 outbreaks and over 27,000 cases of illness that could be connected to exposure to a public pool. The primary culprit was Cryptosporidium, a parasite found in feces that causes intestinal distress. The determined little bugs can survive for up to seven days after encountering the CDC’s recommended levels of one to three parts per million (PPM) of free chlorine. Even if the pool is being cleaned and maintained properly, Cryptosporidium can idle long enough to infect someone else. The report also indicated that Legionella (which causes Legionnaire’s disease) and Pseudomonas (responsible for ear infections and folliculitis) were found in some of the pools.

The problem is likely the result of swimmers entering the pool while suffering from an upset stomach and leaving trace fecal matter behind. The CDC recommends that you not enter a public pool if you feel unwell, that you ask for a pool inspection report if you’re concerned about the hygiene of the facility, and that you absolutely not swallow any water. The agency also recommends that any pool owner who has experienced a “diarrheal incident” in their water opt for hyperchlorination to kill bacteria.

[h/t Men’s Health]

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