Scientists have been studying how people use money for long. Now they're finding some theories may apply to one group of monkeys.

    Researchers recently taught six monkeys how to use money. They gave the monkeys small metal disks(圆片) that could be used like cash and showed them some yummy apple pieces. The monkeys soon figured out that if they gave one of the disks to a scientist, they'd receive a piece of apple in return.

    If you think that is all the monkeys can figure out, you are wrong. Two researchers, Jake and Allison, acted as apple sellers in the experiments. The monkeys were tested one at a time and had 12 disks to spend in each experiment. Jake always showed the monkeys one apple piece, while Allison always showed two pieces. But that's not necessarily what they gave the monkeys. The number of apple pieces given for a disk was determined at random.

    Experiment One: Allison showed two pieces of apples but gave both pieces only half the time. The other half, she took one piece away and gave the monkey just the remaining piece. Jake, on the other hand, always gave exactly what he showed: one piece for each disk. The monkeys chose to trade more with Allison.

    Experiment Two: Allison continued to sometimes gave two pieces and sometimes one piece. But now, half the time, Jake gave the one apple piece he was showing, and half the time he added a bonus. Guess what? The monkeys chose to trade more with Jake.

    In the first experiment, the monkeys correctly figured out that if they traded with Allison, they'd end up with more treats. In the second one, when a monkey received two pieces from Jake, it seemed like again. When Allison gave the monkey only one piece instead of the two she showed, it seemed like a loss. The monkeys preferred trading with Jake because they'd rather take a chance of seeming to win than seeming to lose.

    We also sometimes make silly business decisions just to avoid the feeling that we're getting less, even when were not. Would you have made the same choices?

    Before a new type of airplane goes into service, every part of it is tested again and again. But there are two tests that are more important than all the others.

    The first is called the "tank test". A modem airplane must fly very high in the sky. Air must be pumped into the plane so that the passengers can breathe. The metal structure (结构)of the plane has to be very strong for this reason. When the plane is filled with air, the air presses against the skin of the plane inside. The pressure (压力) on a small window is like a huge foot that is trying to get out. If a small part of the plane were to fail, the plane would explode in the sky. To test the structure of the plane, the plane is lowered into a huge tank or container of water. Then it is filled with air. Vne pressure inside the plane is greater than it ever will be when it is high up in the air. Finally, there is an explosion. This does not cause so much damage inside the water tank as it would anywhere else. Engineers can discover which part of the plane has broken. Then that part is made stronger.

    The most dangerous test happens when the new plane is going through test flights in the air. The test pilot must find out exactly what happens when the engines (发动机) are all shut off at once. The plane begins to fall like a stone. It is the pilot's job to find out how he can get control of the plane again. These two tests are examples of how planes are made safe before they ever carry passengers.

    Everyone needs friends. We all like to feel close to someone. It is nice to have a friend to talk，laugh and do things with. Surely，there are times when we need to be alone. We don't always want people around. But we would feel lonely if we never had a friend.

    No two people are the same. Sometimes friends don't get along well，which doesn't mean that they no longer like each other. Most of the time they will go on being friends. Sometimes friends move away，then we feel very sad. We miss them much，but we can call them and write to them. Maybe we would never see them again，and we can make new friends. It is surprising to find out how much we like new people when we get to know them. Families sometimes name their children after a close friend. Many places are named after men and women，if they are friendly to people in a town. Some libraries are named this way. So are some schools. We think of these people when we go to these places.

    There's more good news for people who have friends. They live longer than those people who don't. Why? It could be that they are happier. Being happy helps you stay well. Or it could be just knowing that someone cares. If someone cares about you，you take better care of yourself.

    Last week, two companies, Kitty Hawk and Uber, announced their plans to bring flying cars to reality very soon.

    Imagine never having to worry about traffic, stop lights, or road construction. A flying car would get to a place much faster than one travelling by road. On the other hand, imagine having to avoid drones (无人驾驶飞机) and other flying cars. Also, what if your battery dies when you are in the air? And, how will you know where to land?

    Kitty Hawk is a start-up tech company supported by Google co-founder, Larry Page. According to the Kitty Hawk website, its car will be able to travel at speeds up to 40 kilometers an hour in the air. It says under US aviation law such a machine “does not require registration or a pilot's license and may be flown in uncongested (不拥挤的) areas for recreational purposes.” As of now, the car can only be flown over fresh water.

    Kitty Hawk is making a list of people interested in buying the flying car. They must pay a deposit of US$100. Those who get their names on the list early will receive US$2, 000 off the final cost of the car. However, Kitty Hawk has not yet announced the price. Kitty Hawk expects its first flying cars will go on sale by the end of this year.

    At a conference last week, Uber announced plans for flying taxis to begin carrying passengers. Unlike the Kitty Hawk company, Uber does not plan to build its flying cars. Instead, it will use the resources of partner companies.

    Like the Kitty Hawk car, Uber flying taxis will use electric power. Uber says its flying taxis could travel up to 241 kilometers an hour. The company said that could reduce the travel time between San Francisco and San Jose, California from two hours on the road to 15 minutes in the air.

    Riders could use the Uber app to book a flying taxi to take them to their destinations. The company has not yet said how costly air taxi travel would be compared to road taxi travel.

    Electric Shock

    Injuries caused by electric shock are fairly common. When a person has received an electric shock, no one should go near him/her until the current has been turned off.

    If a shock occurring at work or at home causes someone to lose consciousness（知觉）, electrical connection must be broken before anyone tries to give assistance. You should either turn off the switch at the mains or, if that is not possible, push the person away with a dry piece of wood.

    Treatment of Shock

    Look out for signs of shock. People who have been injured or who may have lost a lot of blood, or those who have had heart attacks, may be in deep shock. The signs to look for are faintness, paleness, a moist, sticky skin, shallow, rapid breathing and a fast but weak heartbeat.

    Shock can prove fatal, and it is essential to do something to prevent its developing. The best way to treat or prevent shock is to keep the patient lying down , better with the legs higher than the head; if possible, raise the lower part of the body on a rolled-up packet or similar object. Make the patient as comfortable as possible, loosening any tight clothing, and comfort him/her because fright increases the effects of shock.

    Families should reduce exposure to synthetic chemicals found in food colorings, preservatives and packaging materials as a growing body of research shows they may harm children's health, according to a policy statement and technical report from the American Academy of Pediastrics released online.

    The statement also suggests improvements to the food additives regulatory system, including updating the scientific foundation of the U.S. Food and Drug Administrations safety assessment retesting all previously approved chemicals.

    Leonard Trasande, the author of the policy statement, to tell us more about these concerns.

Q: What are the growing number of studies showing us?

A: Over the past two decades, an accumulating body of science suggests some food additives can interfere with a child's hormones, growth and development.

    Potentially harmful effects of food additives are of special concern for children because they are more sensitive to chemical exposures because they eat and drink more relative to body weight, than adults do and are still growing and developing. An early injury to their organ systems can have lifelong and permanent consequences.

Q: What additives does the statement highlight?

A: The additives of most concern, based on rising research evidence cited in the report, include:

    Bisphenols, such as BPA, used to harden plastic containers and line metal cans, can act like estrogen（雌激素）in the body which may potentially change the timing of puberty, decrease fertility, increase body fat and affect the nervous and immune systems. BPA is now banned in baby bottles.

    Phthalates, which make plastic and vinyl tubes used in industrial food production flexible, may affect male genital development increase childhood obesity and contribute to cardiovascular disease. In 2017, the Consumer Product Safety Commission banned the use or some phthalates in child-care products such as teething rings.