Roanoke Times
Copyright (c) 1995, Landmark Communications, Inc.
DATE: THURSDAY, June 22, 1995 TAG: 9506230004
SECTION: EXTRA PAGE: 3 EDITION: METRO
SOURCE: JOEL ACHENBACH
DATELINE: LENGTH: Medium
A: All day long you probably try to behave like a normal, decent, rational human being. By night, you go to sleep and become Insensible Person. Your brain is awash in images that are illogical, weird, and/or morally bankrupt.
But even though all things seem possible in dreams, some things never happen. You don't smell or taste anything. You don't feel the things you are doing, either. Even in the most vivid dream you never detect the touch of another person. You don't feel hot and cold. And you don't feel pain.
That's why the ancient test for finding out if you are awake or dreaming is to pinch yourself.
Some people may protest that they have smelled things and felt things in dreams. Such sensations may be possible once in a while. But they're noticeably rare, and chances are that when you ``smell'' flowers in a dream you are merely seeing pretty flowers and, later, when reconstructing the narrative, inserting the odor.
Why are so many sensations missing from dreams? Simple: Because the body has to be vigilant for danger.
For example, dreams are odorless because your brain has to be prepared to smell real-life fires, or gas leaks, or nasty wolves wandering up to eat you.
Sleeping is an activity that renders us vulnerable. But your sleeping brain is not completely ignorant of the world around you. Even when you are conked out, your brain is carefully monitoring sounds, smells, temperature, touch and the position of your limbs.
The ``vigilance hypothesis'' was advanced in 1993 by anthropologist Donald Symons in the journal Cognition. Evolution, he writes, ``has disfavored the occurrence during sleep of hallucinations that compromise external vigilance.''
Sound is a bit tricky, though. You do seem to hear things in dreams, right? So doesn't that contradict the presumption of the vigilance hypothesis? Shouldn't dreams be silent movies so that you can easily detect the sound of someone breaking into your home?
Symons' answer: ``The vast majority of the `auditory' sensations that occur in dreams very likely consist of speech and other human vocalizations, and dreamed speech is generated by the mechanisms of speech production, not by those of auditory perception.''
So you see, the part of your brain that hears things is not conjuring up sounds in your dream. That part of your brain is still ready to pick up the sound of a crying baby. The dream ``sound'' comes from a different part of the brain, the discursive, yappy area that just can't shut up.
As Freud put it, a dream conversation is ``quasi heard or said.'' The sound isn't vivid at all; it's almost a telepathic conversation.
One last thing: You may have noticed that if you fall off a cliff in a dream, you wake up before you hit the bottom. This is because your heart starts pounding and the adrenaline stirs you from sleep. But it's also because your brain doesn't allow you to experience the pain or even the sensation of hitting the ground. You just can't dream it, period.
(And if you do: You die.)
Q: Why is dirt dirty? And why does beach sand seem so clean?
A: It's the clay. Dirt is dirty because it contains clay, which sticks to everything, getting into the pores of your skin and the fabric of your clothes. It is so sticky because of what the experts call the ``double-gooey layer.''
Clay is by definition a substance with no grit whatsoever. You can rub it in your hand and feel nothing but goo. At the microscopic level, clay is a compound of thousands of particles, adhering to one another not just with water but with electrically charged particles. The charged particles form a layer above and below every little wad of clay: thus clay is ``double-gooey.''
``Clay is what makes things really dirty. If you just had silt it wouldn't be as much mess,'' says Stephen Leatherman, director of the Laboratory for Coastal Research at the University of Maryland.
To wash a pair of dirty blue jeans, you need something that can break into those charged particles, wedge them apart, and dissipate the little wads of clay. (We recommend detergent.)
As for beach sand: It's already washed. (We are itching to make a Tide joke but never mind.) All the silt and clay and tiny wads of gunk and bacteria and flecks of skin and whatnot that you might find in regular soil can be easily suspended in water and washed out to sea. All that remains are the large grains of sand, by definition between 64 microns and 2 millimeters in diameter.
Those grains are crystals, mostly of quartz. They don't adhere to anything, not even to each other. Now you may argue that they clearly stick together, as when making a sand castle. That, however, is just the surface tension of the water at work.
Wander onto a sand dune, and you'll see that the sand is so dry it will easily brush right off your clothes. Of course days later you will still find some of it wedged here and there.
by CNB