Try this: For an entire day, forget about the clock. Eat when you're hungry and sleep when you're tired. What do you think will happen?

    You may be surprised to find that your day is much like most other days. You'll probably get hungry when you normally eat and tired when you normally sleep. Even though you don't know what time it is, your body does.

    These patterns of daily life are called circadian rhythms, and they are more than just habits. Inside our bodies are several clocklike systems that follow a roughly 24-hour cycle. Throughout the day and night, our internal clocks direct changes in temperature, body chemicals, hunger, sleepiness and more.

    Everyone's rhythms are unique, which is why you might like to stay up late while your sister always wants to go to bed early. But overall, everyone is programmed to feel tired at night and energetic during the day.

    Scientists have known for a long time that the light of day and the dark of night play important roles in setting our internal（内部的） clocks. Now, new discoveries are giving scientists insights into how these clocks work.

    Learning about our body clocks may help scientists understand why problems arise when we act out of step with our circadian rhythms. For example, traveling across time zones can make people wake up in the middle of the night. Regularly staying up late can make kids do worse on tests and quizzes. And working shifts at night leads to higher rates of heart disease, diabetes and obesity.

    “There is a growing sense that when we eat and when we sleep are important parts of how healthy we are,” says Steven Shea, Director of the Sleep Disorders Research Program at Brigham and Women's Hospital in Boston.

    Scientists still aren't sure why the timing of sleep matters so much, Shea says. But research findings suggest that our circadian rhythms are more important than we give them credit for.

    “During the night, we are prepared to sleep,” Shea says. “During the day, we are prepared to eat and move around. If you reverse (颠倒)what you are doing, everything is out of phase. That can have unfavorable consequences.”

    A report says older adults who test their minds with increasingly difficult projects have better mental ability than those who do less demanding activities.

    To keep our brains sharp as we age, we are often told to keep our minds active. As the old saying goes, “Use it or lose it.” But, there is very little scientific evidence to support than.

Denise Park is head of the university's Center for ? Vital Longevity. She designed a study in which she and her tern placed 221 healthy aging and older adults into one of three groups.

    “We asked people to learn new things, like quilting or photography. We asked other people to just do fun things like being in a social group function but were not likely to have a very large effect.”

    The subjects took part in their assigned activities for 15 hours a week over three months. At the end of that time, the researchers found that the adults who learned new skills, such as digital photography, showed the greatest improvements on memory tests.

    No improvements were seen in the results of those in the social group that did activities together like going on field trips. There were also no improvements among the third group that listened to classical music or did crossword puzzles.

    Denise Park believes one reason for improved memory in the active learning group is that its members were being pushed to learn new skills. The other groups took part in what she call receptive activities. Learning new skills may not cure age-related mental decline. But, Ms. Park thinks being mentally active slows down the process.

Denise Park says the latest information shows that the improvements lasted for at least a year. She and her team plan to do longer follow-up studies with all three groups. She also is interested in learning whether taking part in demanding mental activities delays the development of conditions like Alzheimer's disease.

    You dash through a crowded railway station, tripping over bags, spilling (泼出) your coffee, only to have the doors slide shut in your face, leaving you breathless on the platform as the train pulls away,

    But at least, if you're in France, someone may be playing the piano for you. But it won't be performed by a paid musician, or even a street entertainer playing for coins. It will just be a random passer - by, jamming for the fun of it on one of the pianos that the national railroad company, S. N. C. F., has fixed in nearly 100 stations across France. They are free for anyone to play, and travelers from all walks of life have taken to doing just that.

    Gares & Connexions, the S. N. C. F. division that manages its stations, rents the instruments from the producer, Yamaha: which maintains them and tunes them every month or two. The first one was set up in the Gare Montparnasse in Paris in 2012.

    The music, mixed with the sounds of shouting passengers, screaming trains and rolling suitcases, gives French stations a special soundscape. The amateur musicians have included Irish soccer fans and even babies. In 2014, Gares & Connexions and Yamaha organized a nationwide contest called Your Turn to Play, asking participants to submit videos of themselves using one of the pianos. It drew nearly 900 entries.

    Isn't the railroad company taking a big chance? Apparently not: “None of the instruments has been vandalized to this day, or even merely damaged,” said Claire Foumon, a spokeswoman for Gares & Connexions. “They are shared and respected by all.”

    So if you miss a train in Paris; Bordeaux or Marseille one day, perhaps someone will be playing a favorite piece that will ease your pain. Or perhaps you'll sit down and play your annoyance away yourself.

    You probably know that frogs hop (双足跳). But did you know that there's a small frog in the Pacific Northwest that belly flops (肚子先着水)? It's called a tailed frog.

    Dr. Rick Eisner, who has been studying tailed frogs for the past few years, says, "I've looked at thousands of jumps and have never seen them land on their feet like other frogs." Most of the time, tailed frogs land on their stomachs and then bring their back legs in to prepare for another jump.

    Eisner first noticed these frogs because of the way they swim. Other frogs kick both of their back legs at the same time. But when a tailed frog swims, it pushes first with one leg and then the other.

    To try to find out why tailed frogs bellyflop, Eisner and other scientists collected and filmed different kinds of frogs. They found that all of the frogs start their jumps the same way: They hold out their legs. The change comes in the landing. Tailed frogs can't move their back legs as quickly as other frogs do. Maybe they don't need to. Tailed frogs live around water and quickly jump into the water to escape danger.

    Early frogs developed around watery areas and could jump quickly into the water to escape danger. Scientists think those frogs blended in with (与…融合在一起) the green plants on the side of the rocky rivers, just like today's tailed frogs. "I would guess that other animals would have problems detecting them," explains Eisner. When other animals find those early frogs, the frogs could jump into the river. They didn't need to continue hopping.

    Tailed frogs and other kinds of frogs went their own ways about 200 million years ago. Tailed frogs stayed by rivers. Other kinds of frogs moved to places where new hopping skills allowed them to survive.

    Does the amount of cash in a lost wallet influence how likely a person is to return it? Classical economic theories suggest that the greater the appeal, the less likely we are to be honest—but a new study turns the idea on its head, finding altruism(利他主义), and a powerful hate for viewing oneself as a "thief" outweigh the financial attraction.

    A team of researchers conducted a huge experiment concerning 355 cities in 40 countries. More than 17,000 identical wallets were dropped off at public places, each containing a grocery list, a key, and three business cards in the local language using made-up names and an email address. Some had no money while others contained the equivalent (等值) of $13.45.

    According to the research, people on average returned 40% of wallets with no money in them but 51%with money. It also shows extreme differences between countries. But although rates of people's honesty varied greatly from country to country, one thing remained remarkably constant: wallets with money, as opposed to no money, raised reporting rates.

    In the US, the UK and Poland, they repeated the experiment with even more money: $94.15, which increased reporting rates by an average of 11% compared to the smaller amount. They also found that having a key expanded reporting rates by 9.2%.

    The findings, which run counter to a fundamental principle of classical economics, suggest honesty, altruism and self-image can sometimes be more influential than economic self-interest.

    A purely economic approach to behavior suggests people would keep the wallets with the larger amounts of money due to the increased financial reward, but economics often doesn't account for a person's sense of honesty or self-image, according to behavioral scientists. Altruism also influenced the findings, the researchers say. Since the key is valuable to the owner but not the finder, this pointed toward an altruism concern in addition to the cost of negatively updating one's self image.

A mix of anxiety rising in my chest and a voice at the back of my mind shouting ‘what's wrong with me?'-it's how I've felt about rejection my whole life.

 The earliest rejection I can remember was on my first day of school. I started the term late due to illness and the teacher asked the class who would play with me at break. The silence was deafening. Now, a bit of online dating sees us rejected by half the town before we've even started our day. There's not a break at work. Is there a worse feeling than hitting the final slide on your presentation, boldly asking 'any questions?' and looking around the room to see everyone on their phones?

We need to build resilience. For me, this has come in two stages. First, I spent time listening to the voice of fear that saw each rejection as proof that there was something wrong with me. When I analysed it, I could see it was rarely about me. Perhaps the guy I was talking to was too busy to reply. It was likely that the magazine I'd sent a passage to already had an article on that topic. Now, I assume it's about me 20 per cent of the time-and I can live with that.

 The other thing I do is practice rejecting. Because I hate rejection, I shy away from being the rejector, which means I either please people or avoid tricky situations. Instead, I've come up with a few lines for when I want to say no: 'That sounds great but it's not for me; thank you for asking but I decline; it was lovely but I think we should leave it there.' It's never pleasant to reject a person but there is a kind way to do it. With resilience and clarity, we can see the plus sides of rejection: it frees us up to do something else, be with someone else and be happier. We can't complain about that.