Even if trees cannot walk, they are still on the move.

    In parts of the Arctic, entire forests are moving northward. Across the Arctic, temperatures are rising faster than anywhere else in the world. As that happens, the tree line that marks where forests stop and the treeless tundra (冻原) starts has been shifting northward. Trees growing along the tree line must protect themselves from the cold wind. To dothis, plants tend to grow horizontal (水平的) branches low to the ground. The energy it takes for trees to grow this way means they don't have enough energy to make seeds.

    But as Earth's climate has been warming, trees no longer have to just grow horizontally. Many can instead grow up toward the sky. This takes less energy. And with all that leftover energy, these trees have started producing more seeds. This happens especially in places where white spruce (白云杉) grows.

    White spruce, which is a North American tree, is quite able to produce a lot of seeds, which can move long distances in the wind. When wind­blown seeds end up on the tundra beyond the tree line, they eventually can sprout(发芽) new trees. This explains how a forest can move. Of course, the process would work only if the tundra were warm enough. But in recent years, the whole planet has been warming.

    New trees will provide shelters for some snow. Keeping the sun's rays from making the white surface disappear. Instead, the trees absorb the sun's heat. This warms the surrounding air. The extra warmth encourages even more trees to produce seeds. That further boosts a forest's ability to expand. In addition, more trees will trap more snow, preventing much of it from being blown away. Snow can trap heat in the soil below, which encourages trees to grow. The recent rise of temperatures has helped more trees grow past the tree line. People worry about impacts on the animals that depend on frozen conditions for food and shelter.

    Sports can help us a lot. Taking exercises can make us strong. In collective（集体的）sports like basketball, volleyball or football, we will learn the importance of cooperation(合作). And sports can also help us relax after work or study.

    However, as the saying goes, "there are two sides of everything." Sometimes we may hurt other players or ourselves if we are not careful enough when participating(参加) in sports activities. What's more, too much or hard practice can be bad for our health.

    Sports can make us healthy both physically and psychologically(心理地). It is also a good way for people to know each other and can improve friendship between people. So long as we are careful enough, sports can do us nothing but good.

    In recent years, a growing body of research has shown that our appetite and food intake are influenced by a large number of factors besides our biological need for energy, including our eating environment and our perception（感知）of the food in front of us.

    Studies have shown, for instance, that eating in front of the TV (or a similar distraction) can increase both hunger and the amount of food consumed. Even simple visual clues, like plate size and lighting, have been shown to affect portion size and consumption.

    A new study suggested that our short-term memory also may play a role in appetite. Several hours after a meal, people's hunger levels were predicted not by how much they'd eaten but rather by how much food they'd seen in front of them—in other words, how much they remembered eating.

    This disparity (新旧研究的差异）suggests the memory of our previous meal may have a bigger influence on our appetite than the actual size of the meal, says Jeffrey M. Brunstrom, a professor of experimental psychology at the University of Bristol.

    "Hunger isn't controlled individually by the physical characteristics of a recent meal. We have identified an independent role for memory for that meal," Brunstrom says. "This shows that the relationship between hunger and food intake is more complex than we thought."

    These findings echo earlier research that suggests our perception of food can sometimes trick our body's response to the food itself. In a 2011 study, for instance, people who drank the same 380-calorie milkshake on two separate occasions produced different levels of hunger-related hormones （荷尔蒙），depending on whether the shake's label said it contained 620 or 140 calories. Moreover, the participants reported feeling more full when they thought they'd consumed a higher-calorie shake.

    What does this mean for our eating habits? Although it hardly seems practical to trick ourselves into eating less, the new findings do highlight the benefits of focusing on our food and avoiding TV and multitasking while eating.

    The so-called mindful-eating strategies can fight distractions and help us control our appetite, Brunstrom says.

    You can relax if remembering everything isn't your strong suit. Recent research makes the case that being forgetful can be a strength—in fact, selective memory can even be a sign of stronger intelligence.

    Traditional research on memory has focused on the advantages of remembering everything. But looking through years of recent memory data, researchers found that the neurobiology of forgetting can be just as important to our decision-making as what our minds choose to remember.

    Making intelligent decisions doesn't mean you need to have all the information at hand. It just means you need to hold onto the most valuable information. And that means clearing up space in your memory palace for the most up-to-date information on clients and situations. Our brains do this by creating new neurons(神经元）in our  hippocampus, which have the power to overwrite(重写)existing memories that are influencing our decision-making.

    If you want to increase the number of new neurons in our brain's learning region, try exercising. Some aerobic exercise like jogging, power walking and swimming has been found to increase the number of neurons making important connections in our brains.

    When we forget the names of certain clients or details about old jobs，the brain is making a choice that these details don't matter. Although too much forgetfulness can be a cause for concern, the occasional lost detail can be a sign of a perfectly healthy memory system. The researchers found that our brains facilitate decision-making by stopping us from focusing too much on unimportant past details. Instead，the brain helps us remember the most important part of a conversation.

    We can get blamed for being absent-minded when we forget past events in perfect detail. These findings show us that total recall(记忆)can be overvalued. Our brains are working smarter when they aim to remember the right stories, not every story.

    On a comfortable sunny Sunday, I was going to meet an old university friend I hadn't seen for years, and was really excited to hear all his news. My train was running a little late, but that was no big problem — I could text him to say I would be delayed. He would understand. But.. . where was my mobile phone? I had that familiar sinking feeling. Yes, I'd left it at home.

    No mobile phone . I'm sure I'm not alone in feeling anxious, on edge and worried when I don't have my phone with me. In fact, I know I'm not alone: two-thirds of us experience this " nomophobia".

    That's according to a study which surveyed 1,000 people in the UK about their relationship with mobile phones, which says we check our mobile phones 34 times a day, that women are more "nomophobic" than men, and that 18-24-year-olds are the most likely to suffer fear of being without their mobiles: 77% of them say they are unable to be apart from their phones for more than a few minutes.

    Do you have "Homophobia"?

    •You never turn your phone off.

    •You obsessively (着迷似地)check for texts, missed calls and emails.

    •You always take your phone to the bathroom with you.

    •You never let the battery run out.

    It's funny to think that around 20 years ago the only people with mobile phones would be business persons carrying their large, plastic "bricks". Of course, these days, mobile phones are everywhere. Its subscriptions has outnumbered people across the world.

    And when there are more phones than people in the world, maybe it's time to ask who really is in charge? Are you in control of your phone, or does your phone control you? So, what happened with my university friend? When I arrived a few minutes late he just laughed and said: "You haven't changed at all — still always late!" And we had a great afternoon catching up, full of jokes and stories, with no interruptions and no nagging (唠叨的)desire to check my phone.

    Not having it with me felt strangely liberating. Maybe I'll leave it at home on purpose next time.