It's a popular belief that a fish's memory lasts for only seven seconds. It may seem sad to think that they don't remember what they've eaten or where they've been, and they don't recognize you or any of their friends—every moment in their life would be like seeing the world for the first time.

    But don't be so quick to feel sorry for them. A new study has found that fish have a much better memory than we used to think. In fact, certain species of fish can even remember events from as long as 12 days ago.

    In the study, researchers from MacEwan University in Canada trained a kind of fish called African cichlids to go to a certain area of their tank to get food. They then waited for 12 days before putting them back in the tank again.

Researchers used computer software to monitor the fish's movements. They found that after such a long break the fish still went to the same place where they first got food. This suggested that they could remember their past experiences.

    In fact, scientists had been thinking for a long time that African cichlids might have a good memory. An earlier study showed that they behaved aggressively in front of certain fish, perhaps because they remembered their past “fights”. But until the latest findings, there was no clear evidence.

    Just as a good memory can make our lives easier, it also plays an important part when a fish is trying to survive in the wild.

    “If fish are able to remember that a certain area contains safe food, they will be able to go back to that area without putting their lives at risks,” lead researcher Trevor Hamilton told Live Science.

    For a long time, fish were placed far below chimpanzees, dolphins and mice on the list of smart animals. But this study has given scientists a new understanding of their intelligence.

    Chocolate is good for your heart, skin and brain. Usually, people think that chocolate is bad for their health. They describe chocolate as “something to die for” or say “death by chocolate”. Now they should bite their tongues! Evidence is showing that some kinds of chocolate are actually good for you in the following ways:

    A happier heart

    Scientists at Harvard University recently examined 136 studies on cocoa—the main ingredient in chocolate and found that it does seem to strengthen the heart．Studies have shown heart benefits from increased blood flow. These benefits are the result of coca's chemicals, which seem to prevent both cell damage and inflammation (炎症)．

    Better blood pressure

    If yours is high, chocolate may help. Jeffrey Blumberg from Tufts University recently found that people with high blood pressure who ate 3.5 ounces of dark chocolate per day for two weeks saw their blood pressure drop quickly.

    Muscle magic

    Chocolate milk may help you recover after a hard workout (锻炼). In a small study at Indiana University, people who drank chocolate milk between workouts did better on a tiredness test than those who had some sports drinks.

    Better for your skin

    German researchers gave 24 women a half-cup of special cocoa every day. After three months, the women's skin was moister (滑润的) and smoother. The research shows that chocolate helps protect and increase blood flow to the skin, improving its appearance．

Brain gains

    It sounds almost too good to be true, but research suggests that chocolate may improve your memory, attention span, reaction time, and problem-solving by increasing blood flow to the brain．

    Dogs were living as companions to the early settlers of North America over 10,000 years ago. The oldest domestic dogs in the Americas were thought to be around 9500 years old. Angela Perri of Durham University, UK, and her colleagues have carried out fresh radiocarbon dating on the two dog skeletons that gave this date, discovered in the prehistoric Koster site in Illinois, and found they were even older: around 10,100 years old.

    A third dog from another Illinois site called Stilwell II was older still, at 10,190 years old. That makes it the oldest known domesticated dog in the Americas. The team concluded that all three dogs were domesticated as they skeletons were complete and unskinned, and so hadn't been butchered for food. They had also been carefully buried, evidence they were valued by their owners. The Stilwell II dog, which probably resembled a small English settler, was under what seemed to be the floor of a living area. It is unclear why it took so long for tame dogs to arrive in the Americas, given that they were domesticated at least 14,000 years ago in Eurasia. By this time, people were already moving into North America from Siberia; there is evidence some reached Chile 18,500 years ago. Geneticists have found signs of at least three waves of migration over the following millennia. There is no evidence that domestic dogs accompanied them. “We don't know if dogs were part of the first waves of immigration to the Americas" says Luc Janssens of Ghent University in Belgium. "It could be so, but no archaeological bones have yet been found." It is "overwhelmingly probable" that some of the early settlers did bring dogs to the Americas, but they may not have had "the time or the spiritual compulsion to bury them", says Pat Shipman of Pennsylvania State University.

    Experts like to say the best form of exercise is whatever kind you'll actually do. But that may not always be the case; new research finds that people who combine exercise with their social lives may be at an advantage over solitary（独自） exercisers. Tennis, badminton and soccer are all better for longevity(长寿) than cycling, swimming, jogging or gym exercise, according to the research.

    The study was based on data from about 8,500 adults who were part of the Copenhagen City Heart Study. They completed a health and lifestyle questionnaire, which included questions about type and frequency of physical activity, and were monitored by the researchers for around 25 years, a period during which about 4,500 of the subjects died.

    Tennis came out on top in the research. Compared with people sitting all day, those who reported playing tennis as their main form of exercise could expect to add 9.7 years to their life time, followed by badminton (6.2 years), soccer (4.7 years), cycling (3.7 years), swimming (3.4 years), jogging (3.2 years) and health-club activities (1.5 years).

    Tennis likely took the top spot because "it's very interactive," says study co-author Dr. James O'Keefe, a physician at Saint Luke's Mid America Heart Institute. "At every point you're talking. It's just a very natural way to emotionally bond with people, besides getting your exercise." But he adds that the study may not have been able to fully account for the fact that wealthier, better-educated people—who tend to be healthier to begin with—may be more likely to play tennis.

    Activities like running and weight lifting still extend your life and offer plenty of other health benefits. But for the best possible benefits, O'Keefe says gym-goers may want to consider combining those workouts with activities that foster social connection.

    O'Keefe, whose exercise typically includes running and weight lifting, says he's even changed his own behavior because of the study: he and his family have taken up badminton.

    "You can't play badminton without feeling like a kid again," he says. "It's just pure fun."

    I stopped to watch my little girl busy playing in her room. In one hand was a plastic phone ; in the other a toy. I listened as she was speaking to her make-believe little friend and I'll never forget the words she said, even though it was imagined.

    She said, "Suzie's in the corner because she's not been very good. She didn't listen to a word I said or do the things she should." In the corner I saw her baby doll well dressed. It was obvious that she'd been put there to sit alone and think.

    My daughter continued her "conversation", as I sat down on the floor. She said, "I'm all fed up and I just don't know what to do with her any more. She cries whenever I have to work and wants to play games too. She tries to help me with the dishes, but her arms just cannot reach... And she doesn't know how to fold towels. I don't have the time to teach. I have a lot of work to do and a big house to keep clean. I don't have the time to sit and play - don't you know what I mean?"

    And that day I thought a lot about making some changes in my life, after listening to her innocent words which cut me like a knife. I hadn't been paying enough attention to what I hold most dear. I'd been caught up in responsibilities that increased throughout the years.

    But now my attitude has changed because in my heart I realize that I've seen the world in a different light through my little darling's eyes. So let the cobwebs(蜘蛛网) cut the corners and the dust bunny rabbit rule the floor. I'm not going to worry about keeping up with them anymore.

    I'm going to fill the house with memories of a child and her mother, for we have only one childhood and we will never get another.

Foldable phones are once again facing questions about their durability(耐久性).The Galaxy Z Flip and the Motorola Razr are now both available to buy in the US-but early reports suggest the screens are easily damaged.

One media published photos of two layers of the Razr's display separating, affecting the touch screen. The Galaxy flip, meanwhile, boasts(自夸)a "flexible glass" display—but tests appear to show it scratching(刮擦)as easily as plastic.

In a statement, Samsung said the display had a protective layer, and had undergone extensive testing. "While the display does bend, it should be handled with care, "it said.

The Z Flip's "pretty thin glass" is one of Samsung's primary marketing messages for the new phone. But a durability test conducted by popular Zack Nelson, a regular buyer, suggested it was no more durable than soft plastic screen, and could even be dented(痕)by fingernail.

Nelson said Samsung's screen scratched exactly how plastic screen would react. "I don't know what material this is, but Samsung definitely shouldn't be calling it glass," he said. He found that the screen of the Motorola Razr scratched as easily but it is not marketed as "glass".

The Motorola Razr was put on sale 13 days ago in the US, but Raymond Wong, an editor says the flexible screen on his handset has already broken. The upper layer of the Razr's screen separated from the bottom, creating "a giant horizontal air bubble" for no apparent reason. He wrote that the fault appeared after 45-minute train ride during which the phone was in his pocket. The screen was completely warped from hinge-to-hinge with the top layer raised like a poorly applied screen protector. But Mr. Wong said that apart from the visual problem, the damage has affected the responsiveness of the touchscreen.