E6


Rattus norvegicus


KLMNO URBAN JUNGLE


The changing natural world at our doorsteps. D.C.’s second-most-successful mammal


Summer provides an abundance of food and vegetation that supports a seasonally swelling population of brown rats.


“Spring and summer are the peak breeding seasons,” says D.C. Department of Health spokeswoman Dena Iverson. “Winter acts as a natural exterminator: When it's cold, rats become stressed and breeding is reduced.”


Unless they’re held in captivity, rats live only about a year, so they reproduce early and oſten.


A rat born in May could already be raising a litter of her own by July. It’s possible that she was impregnated again only 10 hours aſter giving birth and could be expecting another 10 pups before August.


Te omnivorous brown rat In addition to dining on human refuse, rats will eat birds, mice, amphibians, small reptiles, fish, eggs, carrion, pet feces, insects, mollusks, worms, leaves, roots, tubers, wood, bark, stems, seeds, nuts, grains, fruits, nectar, flowers, sap and fungi. If poisoned, they will swallow clay, which absorbs toxins.


SOURCES: D.C. Department of Health; ratbehavior.org; University of Michigan Museum of Zoology


District residents can help curb the rat population by securing garbage, taking uneaten pet food back indoors, clearing the yard of weeds and junk, and restricting rat access to buildings by plugging up any hole larger than the circumference of a quarter. Rats love seeds, so your bird feeder may be attracting more than just doves, sparrows and cardinals.


For help with rodent control, dial the Citywide Call Center at 311. 66


Seeking rat abatement


114 calls made to D.C. rodent control, July 12-19


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The size of the barrel “Getting to the bottom of the


bbl” [July 13] cites Charles A. Whiteshot’s “The Oil-Well Drill- er” saying that Pennsylvania oil producers agreed in 1866 that 40-gallon whiskey


barrels


would be used but “an allow- ance of two gallons will be made on the gauge of each and every 40 gallons in favor of the buyer.” In fact, by around 1700, Penn-


sylvania statute, practical ex- perience and custom made a 42-gallon watertight “tierce” the standard container for ship- ping everything from eel, salmon, herring, molasses, soap, butter, wine and whale oil. These 42-gallon barrels were familiar containers when the petroleum industry was born in 1859 in Titusville. The tierce weighed more than 300 pounds. Twenty would fit on a railroad flatcar. Bigger casks were unmanageable and small- er were less profitable. The 42-gallon standard was adopted by the Pe- troleum Pro- ducers Associa- tion in 1872 and by the U.S. Geo- logical Survey and the U.S. Bu- reau of Mines in 1882.


BRUCEWELLS


Executive Director, American Oil & Gas Historical Society Washington


Attack of the ants Regarding “That antsy feel-


ing” [July 20]: I had the prob- lem for several years of ants appearing in my kitchen every May. Nothing I did got rid of them. Then I read an article recommending the planting of mint along the home’s foun- dation. I did this last fall, and voila! No ants


WASHINGTON POST PHOTO ILLUSTRATION


whatsoever in my kitchen this spring, continuing to the pre- sent.


PATRICIAMINAMI Rockville


I’ve been attacked by ants and I have prevailed. It’s pretty easy if you’re not trying to kill them, just to get rid of them. In- terrupt their pheromone trails. Heloise (of “Hints from” fame) recommends a spray of one part vinegar to three to four parts water, and it works. So do any of the common kitchen spray cleaners, which all have strong scents of one sort or another. I thoroughly spray the counter- top, where they seem to congre- gate, and the windowsills and various construction joints that might be their points of entry to the countertop. I leave the spray on for several minutes and then wipe off. Occasionally I’ll have to repeat these steps on one or two successive days. JOANHARTMANMOORE Alexandria


STEPHEN VAUGHAN/WARNER BROS PICTURES In “Inception,” a team of industrial spies hook themselves up to a machine, go to sleep and enter the dream of the person they’re targeting.


DiCaprio thriller blends science into its fiction


by Rowan Hooper New Scientist


In the new sci-fi thriller “In- ception,” Dom Cobb, played by Le- onardo DiCaprio, is a dream snatcher. He’s an industrial spy who steals secrets by means of “extraction” when his victims are at their most defenseless: when they are asleep and dreaming. But he has an even rarer ability, that of “inception”: He can plant an idea in someone’s sleeping mind, and watch the dreamer act on it when he awakens. “The most resilient parasite is an idea,” he says. “Inception” lies somewhere be-


tween a James Bond film and “The Matrix.” But it does con-


tain some science. Here’s a spoil- er-free guide to the movie’s take on dreams and the unconscious mind.


Is it possible to directly ac-


cess someone’s dreaming mind? In the movie, the dream snatch- ers use a drug called somnacin and a dream machine to upload a scenario into someone’s sleeping mind. One or more of the dream snatchers hook themselves up to the machine, go to sleep them- selves and enter the target’s dream. This fictional dream ma- chine is called a Portable Auto- mated Somnacin IntraVenous (PASIV) Device. A device already exists that can effectively read someone’s mind.


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A functional MRI scanner takes snapshots of brain activity, and then software re-creates images of what the subject was looking at. Researchers say it has the poten- tial one day to record someone’s dream — without the mess and danger (or the fun) of actually sharing that dream. Using a drug like somnacin to access a sleeping mind is not pos- sible, but there are drugs that can drastically modulate our sleep. These include modafinil, which can promote continuous wakeful- ness, and new classes of sleeping pills that can deliver “super sleep,” in which, for instance, four hours of sleep can equate to six. How can I control my dreams? The easiest way to experience a lucid dream — in which the sleep- er is aware he or she is dreaming and can actively participate in the dream — is to train yourself to ask, “Am I dreaming?” while you are asleep. Keen video gamers, prob- ably because they focus on a single task for hours per day, are partic- ularly good at lucid dreaming. The dream team of “Inception” is highly trained at this, which may be why they are able to per- form complex tasks while asleep, such as reading, which most nor- mal lucid dreamers find difficult. Some of the characters in the movie have also militarized their dreamscapes, adding protectors, to guard themselves against in- vasive dream snatchers. Do dreams have to obey the


laws of physics? This is a fondly debated topic,


and “Inception” has it both ways. Sometimes impossible things happen — in one dream Paris gets folded like a huge sheet of paper — and optical illusions become “real.” The endless staircases cre- ated by M.C. Escher, for example, exist in “Inception” dreams thanks to a manipulation some- thing like those that occur in 3-D virtual environments. However, the “Inception” dreams follow some real-life rules. As writer and producer Jeff Warren wrote about his own dream investigations: “Without sensory input, consciousness ap- pears to behave in predictable


ways. Informal laws can be de- duced, for example, the ‘law of self-fulfilling expectations’ (what you expect to happen will hap- pen), the ‘law of narrative mo- mentum’ (linger too long in one place and the dream world begins to fray).” In “Inception,” the dream world


“frays” when external influences from the real world intrude. What is the function of


dreams? Freud thought that dreams ex- pressed our repressed desires. And so they do, sometimes, but much modern research suggests that dreams help in information processing and memory storage. Dreams occur in both rapid-eye movement (REM) sleep and non- REM sleep. REM dreams are more storylike, with emotion and aggression; non-REM dreams of- ten involve friendly social inter- actions. People with depression often experience more REM sleep than non-depressed people. How does subjective time pass in a dream? In “Inception,” dream time runs much more slowly than real time, and there is a scaling effect, such that if you dream within a dream, time passes even more slowly. So five minutes of real time equals one hour of dream time, a five- minute dream inside a dream equals one week of real time, and so on. This is perhaps the cleverest


part of the movie, but though in- tuitively pleasing, there is little evidence for it. In fact, there is some evidence that in lucid dreams, at least, the perception of time is similar to what it is when the dreamer is awake. A more pressing question for researchers is what happens when our brain’s time perception goes faulty. In fact, the illusion of time passing may be created by the brain itself, which is at least as much of a head-scratcher as the plot of “Inception.” health-science@washpost.com


Hooper is news editor of New Scientist magazine, from which this article is adapted. To see the original article, go to www.newscientist.com.


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