Sleep deprivation(缺失)is an important hidden factor in lowering the achievement of school pupils, according to researchers carrying out international education tests.

    It is a particular problem in richer countries with sleep experts linking it to the use of mobile phones and computers in bedroom late at night. Sleep deprivation is such a serious problem that lessons have to be dragged down to a lower level to suit sleep-deprived learners, the study found. The international comparison, carried out by Boston College, found the United States to have the highest number of sleep-deprived students, with 73% of 9- and 10-year-olds and 80% of 13- and 14-year-olds identified by their teachers as being negatively affected.

    In literacy(读写能力) tests there were 76% of 9- and 10-year-olds lacking sleep. This was much higher than the international average of 47% of primary pupils needing more sleep and 57% among the secondary age group.

    Other countries with the most sleep-deprived youngsters were New Zealand, Saudi Arabia, Australia, England, Ireland and France. High-performing Finland is also among the most lacking in sleep. Countries with the best records for getting enough sleep include Azerbaijan, Kazakhstan, Portugal, the Czech Republic, Japan and Malta.

    The analysis was part of the huge date-gathering process for global education rankings, the Trends in International Mathematics and Science Study(TIMSS)and Progress in International Reading Literacy Study(PIRLS)

    “I think we underestimate the impact of sleep. Our data show that across countries internationally, on average, children who have more sleep achieve higher in maths, science and reading. That is exactly what our data show,” says Chad Minnich of the TIMSS and PIRLS International Study Center.

    “It's the same link for children who are lacking basic nutrition,” says Mr Minnich, based at the Lynch School of Education, Boston College. “If you are unable to concentrate, to attend mentally, you are unable to achieve at your best level, because your mind and body are in need of something more basic. Sleep is a fundamental need for all children. If teachers report such large proportions of children suffering from lack of sleep, it's having a significant impact. But worse than that, teachers are having to adjust their instruction based on those children who are suffering from a lack of sleep. The children who are suffering from a lack of sleep are driving down instruction.”

    That means that even the children who are getting enough sleep are still suffering from this sleep-related lowering.

    situation in which they had to observe two circles on a screen.

    At first glance,price-comparison websites are an example of capitalism at its best.But it has caused fierce competition on price and eviscerated profits.Towers Watson,a consultancy,said that "unnecessary" price competition following the rise of comparison sites in Britain had cost insurers ￡1 billion a year.

    Consumers should celebrate that;the firms' losses are their gains.But there is a catch.Comparison sites introduce a new layer of costs,including their own advertising campaigns.In theory,competition in the market for comparison sites ought to keep those costs down.But David Ronayne of Warwick University argues that consumers often lose out from comparison sites.They earn a commission for each shopper who uses them for consumption such as buying insurance.That referral（委托）cost is included in the price the consumer ends up paying.If the increased costs outweigh the saving the comparison enables,consumers end up worse off.

    These worries are not just theoretical.In 2014,Britain's competition regulator found that many comparison sites were using their contracts with retailers（零售商）to ban them from offering lower prices elsewhere.That weakened rivals' incentive（对手的动机）to cut fees,because prices on their site could not fall.By keeping prices similar,the contracts also reduced the incentive for consumers to search on multiple sites,thus helping sites retain their users.

    Weaker incentives to lower commissions mean weaker incentives to lower costs,too.That might explain why comparison websites advertise so heavily,and sometimes offer free gifts to those who use them.In a recent paper,Ben Edelman of Harvard Business School and Julian Wright of the National University of Singapore argue that when a site knows that the prices merchants provide through it will always be the lowest available,it increases investment in attracting customers,safe in the knowledge that the merchants and at last consumers will bear the cost.

    Is there any way to ensure the market for price comparison is competitive?Asking consumers to check multiple websites defeats the point of using them.One solution is to have only one site,but regulate it as a public utility（功用）. Alternatively,the governments could run the site itself.But creating good search and comparison sites may be too hard for them.It is much better to acknowledge that consumers will always have to do some comparison themselves to "keep the system honest".

    Websites that compare the comparison sites can help,although it is easy to see how they could fall prey to the same problems.Any firm with captive users（被动用户）,be it a comparison site a search engine,or a social-media platform,can charge a high price for access to the eyes of its customers.For all their innovation,Internet middlemen are not unlike supermarkets.Shoppers would never imagine that a single store had the lowest price for all the items they need.

    A few years ago, I took a sightseeing trip to Washington, D.C. Standing outside the Ronald Reagan Center, I heard a voice say, "Can you help me?" When I turned around, I saw an elderly blind woman with her hand extended. In a natural reflex, I reached into my pocket, pulled out all of my loose change and placed it on her hand without even looking at her. I was annoyed at being bothered by a beggar. But the blind woman smiled and said, "I don't want your money. I just need help finding the post office."

    In a moment, I realized what I had done. I judged another person simply for what I assumed she had to be. I hated what I saw in myself. This incident re- awakened my belief in humility (谦恭), even though I'd lost it for a moment.

    The thing I had forgotten about myself is that I am an immigrant. I left Honduras and arrived in the U.S. at the age of 15. I started my new life with two suitcases, my brother and sister, and a strong, serious-minded mother. Through the years, I have been a dishwasher, mechanic and pizza delivery driver among many other humble jobs, and eventually I became a network engineer.

    In my own life, I have experienced many open acts of prejudice (偏见). I remember a time, at age 17 — I worked as a waiter, and I heard a father tell his little boy that if he did not do well in school, he would end up like me. I have also witnessed the same treatment of my family and friends, so I know what it's like, and I should have known better.

    But now, living in my American middle-class lifestyle, it is too easy to forget my past, to forget who I am and where I have been, and to lose sight of where I want to be going. That blind woman on the streets of Washington, D.C., cured me of my blindness. She reminded me of my belief in humility and to always keep my eyes and heart open. By the way, I helped that lady to the post office. And in writing this essay, I hope to thank her for the priceless lesson.

    Long before iPhone, the cigarette was the companion of choice for restlessness. And long before Facebook and WeChat, it was tobacco that promised to better your social life. Now, quitting smartphones has become the new quitting smoking.

    Of course, technology does not yellow your teeth, cause disease or lead to cancer. But some individuals are so concerned that device addiction is damaging their mental health. In order to reduce their dependence, even in Silicon Valley, people are turning off the messages that constantly buzz for their attention, banning smartphones from the bedroom and, curiously, changing the colors on their screens to a less tempting scale of gray.

    The big tech companies will have to work out how to respond to this new generation of quitters. Facebook is the first to go public with its attempt, hoping its recent move can make the social network more homely.

Last year the tech industry got a bad name —Big Tech—with unfortunate echoes of other industries that have faced fierce opposition, including Big Tobacco. Like them, the tech industry has to reduce concern from a new generation of activist shareholders （股东） that are questioning its role in the world. These campaigns are never as fierce as those faced by Big Tobacco. In the 1990s, socially responsible investors refused to put money in tobacco stocks.

    It is far difficult for investors to challenge Big Tech and hard to separate the good these companies do in the world-connecting old friends and giving space for people to share their ideas-from the bad. In the meantime, stopping using technology remains problematic. In The World Without Mind: The Existential Threat of Big Tech, Franklin Foer argues that tech should be seen in a similar way to junk food: a convenience that some reject for more continuing nutrition.

    So we need to do more to turn the tide. In the same way that public service announcements made smoking around your children taboo （禁忌）, we can warn parents against losing themselves in their smartphones while taking care of kids. We can also create no-smartphone zones at dinner. Eventually smartphones could be banned from all public places and help us give our attention to the people around us instead.

    Compulsive（强迫的）shoppers may have a new psychological excuse to blame for their wild shopping. Psychologists at the University of Canterbury in New Zealand are studying the "shop-till-you-drop" habit as a behavioral disorder similar to compulsive eating. Compulsive shoppers frequently buy more than they can afford or more than they need, and it causes them distress.

    "It becomes a problem when you are out of control," psychology lecturer Neville Blampied said. "When you are feeling bad and blue, what do you do? Some people eat chocolate cake and ice cream. Some people take the credit card and go out to the shop." Bank managers understand the problem because they have to deal with people who have to be persuaded to stop using their cards drawing money.

    Compulsive shopping was first discovered in 1915, although it was then known as oniomania. Few studies have been done on the problem.

    An advertisement in a Christchurch paper, calling for people to take part in an experimental treatment program designed by Mr Wilson, attracted 10 replies. But the problem, said Mr Wilson, is"clearly not rare". He thinks that compulsive shopping should be treated with drugs." As psychologists we are interested in non-drug treatments for behavioral difficulties," Mr Wilson said.

    Compulsive eaters or shoppers get a kick from their habit. "Both activities provide an immediate kind of kick and you feel a bit better," he said. "You have long-term problems, but human beings are extremely good at not seeing long-term problems and are very sensitive to short-term benefits," he said.

    The aim of the treatment was to help people find better ways of managing their emotions. The program, consisting of 10 one-hour weekly lessons and two follow-up treatments, is loosely based on teaching stress management.

    "You often have to start to get people to correctly recognize their emotions. Not being able to know what you really feel weakens your ability to solve the problems connected with what's making you feel that way," Mr Wilson said.

The Art Institute of Chicago

    Visiting time

    The museum is open daily 10:30 am-5:00 pm. The museum and its shops are closed on Thanksgiving Day, Christmas Day, and New Year's Day.

    Highlights of the Art Institute

    American Art

    Discover how artists have expressed the many aspects of the American experience through the rich variety of this collection. This tour might include the works of artists like Paul Revere, Winslow Homer, and Georgia O'Keeffe.

    Impressionism: Monet, Degas, Renoir and More

    Learn about the color and excitement of late 19th-century life as you view one of the most admired collections of French Impressionism in the world.

    Hidden Histories

    Hear stories about artists and their artworks that may be overlooked or under-appreciated for one reason or another  These could be very small or out-of-the-way works.

    For families with children

    With free admission for kids under 14 and Chicago teens under 18, the Art Institute is the perfect place for a creative outing with the whole family.

    Visit the Family Room in the Ryan Education Center, and introduce your children to the museum's collections with a variety of activities. Assemble (组装)puzzles based on masterpieces in the museum, build architectural wonders with colorful blocks, and learn about art through stories and games. Food is available at an on-site cafe. (Outside food is not allowed to be brought in.)