Scientists think that many animals can’t see colors. The world is black and white to them. Can dogs see colors? Scientists want to know. So the American scientists give the dogs food. They put the food in the box in the same color every time. The dogs see this color and go to eat. The scientists then give the dogs food in a box with another color. But the dogs go to eat the food, too. The colors are all the same to them.

But colors are not all the same to monkeys. The scientists put food in a red box, and do this every day. A monkey always goes to the red box to get food. Then the scientists put food in a blue box, but the monkey doesn’t go to eat it.

In today's world, sleep experts say that for a better night's rest, Americans should turn off their smartphones or iPads before sleeping. Such electronic products make the brain more active, and then influence people's sleep. But according to a latest survey, more than 90% of Americans usually use a computer or some other kinds of electronic products in the hour before bed.

Researchers found that man-made light from some electronic products at night might reduce the levels of the brain chemicals that help sleep. The researchers showed that sitting in the light from tablets clearly reduced the levels of the chemicals which manage our body clocks and play a great role in the sleep cycle.

In the study, the researchers let volunteers read, play games and watch movies on a tablet for different time while measuring how much light their eyes received. They found that sitting for two hours before a bright tablet at night reduced the levels of the chemicals by about 22%.

Studies of students using computers at night have got the similar results. And researchers said that might not only cause sleeplessness, but also increase the risk of obesity(肥胖症), diabetes(糖尿病) and other diseases.

To be on the safe side, the researchers advise us to use computers less before bed, or turn down our screens low.

You wake up one morning, and your head feels like it’s burning. Right away, you think, “Oh, no! I have a fever!” However, when you take your temperature, you see that it’s only 37.2℃.

So, you don’t have a fever. Or, do you? From the standards (标准) in use for a long time, a fever starts at 38℃. Some doctors now don’t agree with that, though. They feel our ideas about fevers are wrong and too old. It’s the same for normal body temperatures.

These doctors argue that everyone’s normal body temperature isn’t 37℃. It’s 36.6 to 38℃ for kids and 36.1 to 37.2℃ for adults. Women also have a higher temperature than men. Besides, people’s body temperatures don’t stay the same all the time.

When your body temperature is around 38℃, you have a fever. Many people think it’s a bad thing, but it’s not. Fevers show that the body is doing its job. It’s fighting the bad viruses (病毒) and bacteria (细菌) in your body.

The body attacks them by turning up the heat. That way, it’s harder for the viruses and bacteria to make copies of themselves. When their numbers go down, the fever does, too.

Mild fevers don’t last long. So, let them do their jobs and don’t treat them. Instead, try to find the cause and treat that. If the fever reaches 39.4℃ or higher, call your doctor. Do the same if the fever lasts longer than three days. Fevers fight to protect us, so they’re our friends, not our enemies.