The more hours that young children spend in child care, the more likely they are to turn out aggressive and disobedient by the time they are in kindergarten, according to the largest study of child care and development ever conducted. Researchers said this correlation (相关性) held true regardless of whether the children came from rich or poor homes, were looked after by a relative or at a center, and whether they were girls or boys.

    What is uncertain, however, is whether the child care actually causes the problem or whether children likely to turn out aggressive happen to be those who spend more hours in child care. It also remains unclear whether reducing the amount of time in child care will reduce the risk that a child will turn into a mean person. What's more, quality child care is associated with increased skills in intellectual ability such as language and memory, leading some academics to suggest that child care turns out children who are “smart and naughty”.

    The government-sponsored research, which has tracked more than 1,300 children at 10 sites across the country since 1991, is bound to cause the debate over child care again: How should people balance work and family? And how should parents, especially mothers. Resolve the demands that are placed on them to be both breadwinners and supermoms?

    That debate was already on display at a news briefing yesterday, where researchers themselves had different opinions about the data and its implications (含义). “There is a constant relationship between time in care and problem behavior, especially those involving aggression and behavior,” said Jay Belsky of Birkbeck College in London, one of the lead investigators of the study who has previously annoyed women's groups because of his criticisms of child care. “On behalf of fathers or mothers?” interrupted Sarah Friedman, a developmental psychologist at the National Institute of Child Health and Human Development (NICHD) and one of the other lead scientists on the study. “On behalf of parents and families,” responded Belsky.

    “NICHD is not willing to get into policy recommendations.” said Friedman, contradicting her colleague. “There are other possibilities that can be entertained. Yes it is a quick solution—more hours in child care is associated with more problems. The easy solution is to cut the number of hours but that may have implications for the family that may not be beneficial for the development of the children in terms of economics.” In an interview after the briefing, Friedman said that asking parents to work fewer hours and spend more time with their children usually meant a loss of family income, which adversely(不利地) affects children.

    Scientists said that the study was highly reliable. But the researchers said they had no idea whether the behavioral difficulties persisted as the children moved to higher grades.

    Getting less sleep has become a bad habit for most American kids. According to a new survey(调查) by the National Sleep Foundation, 51% of kids aged 10 to 18 go to bed at 10 pm or later on school nights, even though they have to get up early. Last year the Foundation reported that nearly 60% of 7- to 12-year-olds said they felt tired during the day, and 15% said they had fallen asleep at school.

    How much sleep you need depends a lot on your age. Babies need a lot of rest: most of them sleep about 18 hours a day! Adults need about eight hours. For most school-age children, ten hours is ideal(理想的). But the new National Sleep Foundation survey found that 35% of 10- to 12-year-olds get only seven or eight hours. And guess what almost half of the surveyed kids said they do before bedtime? Watch TV.

    “More children are going to bed with TVs on, and there are more opportunities(机会) to stay awake, with more homework, the Internet and the phone,” says Dr. Mary Carskadon, a sleep researcher at Brown University Medical School. She says these activities at bedtime can get kids all excited and make it hard for them to calm down and sleep. Other experts say part of the problem is chemical. Changing levels of body chemicals called hormones not only make teenagers' bodies develop adult characteristics, but also make it hard for teenagers to fall asleep before 11 pm.

    Because sleepiness is such a problem for teenagers, some school districts have decided to start high school classes later than they used to. Three years ago, schools in Edina, Minnesota, changed the start time from 7:25 am to 8:30 am. Students, parents and teachers are pleased with the results.

    Give yourself a test. Which way is the wind blowing? How many kinds of wildflowers can be seen from your front door? If your awareness is as sharp as it could be, you'll have no trouble answering these questions.

    Most of us observed much more as children than we do as adults. A child's day is filled with fascination, newness and wonder. Curiosity gave us all a natural awareness. But distinctions that were sharp to us as children become unclear; we are numb(麻木的）to new stimulation(刺激), new ideas. Relearning the art of seeing the world around us is quite simple, although it takes practice and requires breaking some bad habits.

    The first step in awakening senses is to stop predicting what we are going to see and feel before it occurs. This blocks awareness. One chilly night when I was hiking in the Rocky Mountains with some students, I mentioned that we were going to cross a mountain stream. The students began complaining about how cold it would be. We reached the stream, and they unwillingly walked ahead. They were almost knee-deep when they realized it was a hot spring. Later they all admitted they'd felt cold water at first.

    Another block to awareness is the obsession(痴迷) many of us have with naming things. I saw bird watchers who spotted a bird, immediately looked it up in field guides, and said, a "ruby-crowned kinglet" and checked it off. They no longer paid attention to the bird and never learned what it was doing.

    The pressures of "time" and "destination" are further blocks to awareness. I encountered many hikers who were headed to a distant camp-ground with just enough time to get there before dark. It seldom occurred to them to wander a bit, to take a moment to see what's around them. I asked them what they'd seen. "Oh, a few birds," they said. They seemed bent on their destinations.

    Nature seems to unfold to people who watch and wait. Next time you take a walk, no matter where it is, take in all the sights, sounds and sensations. Wander in this frame of mind and you will open a new dimension to your life.

    You can tell a lot about a country by what's on its television sets. Britain's TV screens are completely steeped in class, and have long been so.

    From laughing at poor people in reality shows to laughing at posh people in Downton Abbey, this is how Britain likes to unwind in the evening: by laughing at other classes, and laughing at people for laughing about class.

    Like it or loathe it, many see the class system as a quite essential element of British life, together with our obsession for tea and cake and talking about the weather.

    Whether you are a lord, a lady, or just the king of your own middle class kingdom, everyone in the UK fits into the class system. How the class system works is a hard question even for a British person to answer.

    There are four main groups in the British class system: lower, working, middle and upper class. Although recently the BBC has tried to confuse everyone even more by adding three more categories.

    The British are very aware of class; it is often said that we have an in-built 'class radar'; we pick up on subtle social clues which indicate which class a person comes from. Class is not just about your job, where you live and how much you earn. It's about who you are.

    If you're looking to fully experience Africa's breathtaking scenery, and have an eye for adventure, then there's only one place to be. Here, inside Africa picks four of the best hikes from across the continent.

    ⒈Kilimanjaro

    Make it to the top of Tanzania's 5,895-meter Kilimanjaro, and you'll be standing at Africa's highest point. The mountain is Africa's most-visited hiking destination, attracting tens of thousands of tourists and adventures every year.

    You don't have to a technical climber to climb Mount Kilimanjaro; you just need not be pretty physically fit. There are six routes to choose from difficulty, scenery and success. No special equipment

    ⒉Atlas mountains

    The High Atlas is an impressive mountainous range in central Morocco that hosts North Africa's highest peak. Mount Toubkal, at 4,165 meters. There's a variety of routes to follow during your climb but inexperienced climbers should note that the hike through the mountain's challenging zones is quite demanding.

    ⒊Mount Kenya

    A long-extinct volcano. Mount Kenya is Africa's second-highest peak, at 5,199 meters.

    Lying just south of the equator, the mountain's deep valleys and diverse wildlife will guarantee you wonderful scenery and a fantastic hiking experience.

    The climb, however, to the mountain's steep ice-capped peaks is quite challenging, making it the most technical, probably, in that East African area.

    ⒋Mount Meru

    Mount Meru may forever exist in the shadow of its neighbor, Kilimanjaro, but Tanzania's second-highest mountain (4,565 meters) has its own devotees.

    It's less known, but Mount Meru is for the true enthusiast who wants to experience what very few people actually do.

    Mount Meru is often used by mountaineers to accustom themselves before trying to conquer Kilimanjaro, or by those wanting a hike with the local Massai.

    We tend to think of our dreams as being uniquely personal­nighttime stories built from our own experiences that help us process our day-to-day lives. While dreams can give us a look into our personal selves, scientists have collected data that suggests dreams make their way into our cultural fabric(结构), showing themselves in ways that shape beliefs and expose collective anxieties.

    Roger Ivar Lohmann of Trent University conducted research with the Asabano people of the rainforest of Papua New Guinea, a unique group who didn't have outside contact until 1963. His studies looked at how dreams shape their beliefs and actions.

    According to Lohmann's research, dreams act as a sort of motivator or determinant of Asabano behavior. For instance, a dream may affect the way a person hunts or goes about treating medical conditions. The way dreams determine behavior is due to what Lohmann calls the "night residue" effect. This means that specific memories of dreams can affect the way a person acts when awake and inform their belief system.

    Dreams also seem to have an effect on the way many define themselves within their own cultures, and how sometimes reaching a distinct definition can cause anxiety.

    Matt Newsom of Washington State University spoke with college students in Berlin, and found many students had dreams surrounding conflicting views about their own identities(身份) in relation to what they saw as a return of German nationalism, which is a sensitive subject especially when we think of German identity as it's defined even many years after World War Ⅱ.

    Many students had dreams that centered around anxieties like "Where do I belong?" Many students never talked with one another about identity struggles in their dreams, yet many reported having such dreams. Newsom noted that dreams can be helpful "for identifying (识别) unspoken social and historical anxieties present in a given society."

    All of this research suggests that dreams can do more than help explain the thought of a person; we can learn about entire cultures and collective attitudes as well.