The baby monkey is much more developed at birth than the human baby. Almost from the moment it is born, the baby monkey can move around and hold tightly to its mother. During the first few days of its life the baby will approach and hold onto almost any large, warm, and soft object in its environment, particularly if that object also gives it milk. After a week or so, however, the baby monkey begins to avoid newcomers and focuses its attentions on “mother” — the real mother or the mother-substitute(母亲替代物）.

During the first two weeks of its warmth is perhaps the most important psychological（心理的） thing that a monkey mother has to give to its baby. The Harlows, a couple who are both psychologists, discovered this fact by offering baby monkeys a choice of two types of mother-substitutes — one covered with cloth and one made of bare wire. If the two artificial mothers were both the same temperature, the little monkeys always preferred the cloth mother. However, if the wire model was heated, while the cloth model was cool, for the first two weeks after birth the baby monkeys picked the warm wire mother-substitutes as their favorites. Thereafter they switched and spent most of their time on the more comfortable cloth mother

    Why is cloth preferable to bare wire? Something that the Harlows called contact（接触的） comfort seems to be the answer, and a most powerful influence it is. Baby monkeys spend much of their time rubbing against their mothers' skins, putting themselves in as close contact with the parent as they can. Whenever the young animal is frightened, disturbed, or annoyed, it typically rushes to its mother and rubs itself against her body. Wire doesn't“rub”as well as does soft wire cloth. Prolonged（长时间的）“contact comfort” with a cloth mother appears to give the babies confidence and is much more rewarding to them than is either warmth or milk.

    According to the Harlows, the basic quality of a baby's love for its mother is trust. If the baby is put into an unfamiliar playroom without its mother, the baby ignores the toys no matter how interesting they might be. It screams in terror and curls up into a fury little ball. If its cloth mother is now introduced into the playroom, the bay rushes to it and holds onto it for dear life. After a few minutes of contact comfort, it obviously begins to feel more secure. It then climbs down from the mother-substitute and begins to explore the toys, but often rushes back for a deep embrace（拥抱）as if to make sure that its mother is still there and that all is well. Bit by bit its fears of the new environment are gone and it spends more and more time playing with the toys and less and less time holding on to its “mother.”

    Now many young people are traveling around the world on their own，not because they have no one to travel with，but because they prefer to go alone.

Kristina Wegscheider from California first traveled alone when she was at college and believes that it is something everyone should do at least once in their life. “It opens up your mind to new things and pushes you out of your comfort zone.” Wegscheider has visited 46 countries covering all seven continents.

    In foreign countries，with no one to help you read a map，look after you if you get ill，or lend you money if your wallet is stolen，it is challenging. This is what drives young people to travel alone. It is seen as character building and a chance to prove that they can make it on their own.

    Chris Richardson decided to leave his sales job in Australia to go traveling last year. He set up a website，The Aussie Nomad，to document his adventures. He says he wished he had traveled alone earlier. “The people you meet，the places you visit，or the things you do，everything is up to you and it forces you to grow as a person，” said the 30-year-old man.

    Richardson describes traveling alone like "a shot in the arm"，which "makes you a more confident person that is ready to deal with anything". He said，"The feeling of having overcome something on my own is a major part of what drives me each day when I'm dealing with a difficult task. I walk around with my head up because I know deep down inside that nothing is impossible if you try.”

    The great 19th century explorer John Muir once said，"Only by going alone in silence can one truly get into the heart of the wilderness."

    He looked like a pirate.

    With his handkerchief tied in a knot behind his little nine-year-old head, he looked like a pirate, a sad pirate. The first time little David came to our camp, he was hairless and worn out from medical treatments. He was also very angry.

    Paul Newman's camp counselors (指导老师) were hoping to fill David's days with fun and laughter. But David stayed inside himself, wanting to be alone, or in a corner of the cabin. At this camp for children with life-threatening illnesses, we had seen some pretty tough children worn out by cancer recover full of energy despite their illness. But we saw little progress in David no matter what we tried with him. Five days into the eight-day session saw a quiet, sad little pirate.

    Then something happened on that fifth night. Something at camp that we would call "huge". It was cabin night. That's the time when campers and counselors spend time together in each individual cabin instead of an all-camp activity. Campers love cabin nights because there's always a bedtime snack. On the cabin table that night were bags of potato chips.

    David slowly walked over to the table, leaving his comer to join the rest of us. He took one of the bags of the potato chips and started smashing(弄碎) it with his little fists, as all the other campers looked on in disbelief, I wondered what the cabin counselor would do.

    The college-age volunteer counselor positioned a bag of chips on die table in front of himself, and he, too, started smashing it with his fist. The campers went crazy as everyone ran to the table to get in on the fun of smashing potato chips with their fists.

    Somehow everyone knew, everyone sensed, that anger within him was now being released.

    For the last couple days of the session, David was a different kid. He was a little nine-year-old boy again, trying to fill the hours of each remaining day at camp with as much fun as could be possible.

    Several days after the session, David came back again. This time, there wasn't anything he wouldn't try to fit in to his day. He sure was having a great time at camp. David asked me if I needed an altar(祭坛)boy when I celebrated Mass in the woods. Sure enough, he was my altar boy. I remembered how carefully he listened to me when I talked about death. I said it's only a doorway. You walk through the door and there's the Lord God and behind God a whole line of people waiting to hug you.

    After Mass, he said to me, "Hey Fatha, a door, huh?"

    A couple more days of fun passed and tonight was the talent show. The tradition is that campers and counselors dress up in costumes, and everyone gets a standing applause for singing and dancing or simply just acting like fools on stage.

    The show had begun: lights, camera, action.

    Unfortunately, the only action taking place in our row of seats was little David making his way from counselor to counselor to say an early good-bye to camp. He had become quite ill and had to go to the hospital because of this new crisis.

    When this little nine-year-old pirate stood in front of me, he gave me a hug and a big wet kiss on my cheek. I was crying. He was crying. A whole row of counselors was in tears. After the hug and kiss, he put his hands on my shoulders, and tears still in his eyes, said: "See you on the other side of the door, Fatha."

    In the fight to conserve tropical rainforests, here's a tool you don't often hear about orange peels. Specifically, 12,000 tons of them, dumped (倾倒) on the land. “You don't usually associate waste treatment with biodiversity benefits, something that's good for the environment.

    Tim Treuer is an ecologist at Princeton University, and he's talking about a unique conservation story. It started in the early 1990s, when an orange juice producer called Del Oro set up a company near the Guanacaste Conservation Area in Costa Rica, a region that contains several national parks and a wildlife protection zone.

    Del Oro needed somewhere to dump the orange peels, and the company also owned forested land next to the parkland that it had no intention of growing crops on. So a deal was struck: if Del Oro donated its forested land, it could dump orange peel waste on degraded(退化的) land within the conservation area. Then a thousand dump trucks' worth of orange peels were lying on the land in 1998. “And within about six months the orange peels had been turned from orange peels into this thick black rich soil.”

    “I couldn't even find the site the first time I saw it.” He couldn't find it because, over 16 years, the orange peel waste had sent the land on a journey to become a vine-choked jungle, with three times the diversity of tree species of the neighboring control plot, richer soil and a much thicker covering. In other words, the experiment was a success. The results appear in the journal Restoration Ecology.

    Treuer says perhaps this lesson could be applied elsewhere. “It's a shame that we live in a world with nutrient-limited degraded ecosystems and also nutrient-rich waste streams. We'd like to see those things come together a little bit. That's not license for any agricultural company to just start dumping their waste products on protected areas, but it does mean that land managers, people involved with industrial-scale agricultural operations should start thinking about ways to do thoughtful experimentation to see if in their particular system they can have similar win-win-win results.”

    The most famous war movies reflect the American public's continuous fascination with World War II and the Vietnam War. Many movies of this kind have been well-received when they were first shown, but few of them have enjoyed lasting fame and popularity. The films on the list of the five most famous war movies still remain fresh and are popular among many people.

You've probably heard it a dozen times by now. But here it goes again: Sleep is important. Your mental health and immune (免疫时)system are connected to your sleeping habits. So are your grades, a new study finds. Sleep accounts for nearly one-fourth of the difference among students' grades in a class. So even if you spend hours studying for a test but get too little sleep, you might still do poorly.

Typically, people's sleep schedules are messy and can not be known in advance. Professor Jeffrey Grossman of Massachusetts Institute of Technology in Cambridge wanted to see if sleep links to people's learning performance even when a study was done with people who kept such true-to-life schedules at home. So he turned to Fitbits, which can check how long people sleep and how frequently they wake up. And the researchers looked for 100 students. They focused on these students' sleep patterns in the days and weeks before exams and then compared them to these students' test scores.

"How much time a person sleeps the night. before an exam doesn't affect that person's grade," Grossman says. "A student who sleeps 7 hours every night will do better than a student who sleeps 7.5 hours one night and 6.5 hours another night."

"It's important for people to know that if their Fitbits tell them that they have terrible sleep, that may not actually be so," Michael Scullin, a sleep scientist at Baylor University says. Grossman also raises this point. Fitbit, Inc. makes this advanced tool. But it doesn't share how its tool works. This leaves a question about whether the tool is really correct when checking a student's sleep. Even so, Scullin emphasizes that there are enough data supporting ties between sleep and how well someone performs.

"Students need more sleep and less late evening use of phones and other screens. Even with after-school activities and schoolwork, they need to get enough sleep," Grossman says.