A lot of people feel that it's much harder to learn a foreign language as you grow older—and they're right. A new study found that if you want to achieve the proficiency（精通）of a native speaker, you'd best start when you're 10 years old.

There is a lot of evidence that shows children find it much easier than adults to learn a foreign language, which has made researchers suggest that there is an "important period" for language learning. But until now, no one has really been sure what that age period is. Now. MIT researchers believe they have solved one of those things.

They found that the window starts to close when you're about 10 years old. Although children up to 17 or 18 learn a new language faster than adults, and their ability drops slower than that in adults, it becomes very difficult to reach the proficiency of a native speaker if you start later than age 10.

The findings are based on an analysis of a grammar test taken by nearly 670,000 people. Researchers took snapshots（快照）of thousands of people who were in different stages of learning English. They also used a game called “Which English?” to judge which dialect of English the test-taker speaks. Within hours after being posted on the social media, the 10-minute test "Which English?" spread quickly.

Researchers found that the grammar-learning ability remains strong until age 17 or 18, after which it starts to drop—which was rather unexpected. It's not clear why the drop starts to happen. It may either be a cultural reason or a biological one. You shouldn't let this disappoint you. Even if it's a bit harder, you should try it. It's not just the ability to talk to someone from another country. Studies have shown that learning a second or third language does wonders for your brain and mental health.

Artificial intelligence (AI) technology may soon be a useful tool for doctors. It may help them better understand and treat diseases like breast cancer in ways that were never before possible.

Rishi Rawat teaches AI at the University of Southern California’s (USC) Clinical Science Center in Los Angeles. He is part of a team of scientists who are researching how AI and machine learning can more easily recognize cancerous growths in the breast. Rawat provides information about cancer cells to a computer. He says this data helps the machine learn. “...You can put the data into them and they will learn the patterns and the pattern recognition that’s important to making decisions.”

David Agus is another USC researcher. He believes that “machines are not going to take the place of doctors.” He adds, “Computers will not treat patients, but they will help make certain decisions and look for things that the human brain can’t recognize these patterns by itself.”

Once a confirmed cancerous growth is removed, doctors still have to treat the patient to reduce the risk of cancer returning. The form of treatment depends on the kind of cancer. Currently, researchers take a thin piece of tissue, put it on a small piece of glass and add color to better see the cells. This process could take days or even longer. Scientists say artificial intelligence can do something better than just count cells. Through machine learning, it can recognize complex patterns, or structures, and learn how the cells are organized. The hope is that machines will soon be able to make a quick diagnosis（诊断）of cancer that is free of human mistakes.

“All of a sudden, we have the computing power to really do it in real time...We couldn’t have done this, we didn’t have the computing power to do this several years ago, but now it’s all changed.” Agus adds that the process could be done “for almost no cost in the developing world.” He says that having a large amount of information about patients is important for a machine to effectively do its job in medicine.

A doctor faces a series of critical decisions every day. The best a doctor can do is to make those decisions as informed as possible. Some of them are still hard to make. A doctor can ask people of whom he values their opinions and that’s it. Imagine discussing these with an AI system that is even more rational（理性的）than anyone else.

The University of Southern California researchers are now only studying breast cancer. But doctors predict artificial intelligence will one day make a difference in all forms of cancer.