If you ever get the impression that your dog can "tell" whether you look content or annoyed, you may be onto something. Dogs may indeed be able to distinguish between happy and angry human faces, according to a new study.

Researchers trained a group of 11 dogs to distinguish between images（图像）of the same person making either a happy or an angry face. During the training stage, each dog was shown only the upper half or the lower half of the person's face. The researchers then tested the dogs' ability to distinguish between human facial expressions by showing them the other half of the person's face or images totally different from the ones used in training. The researchers found that the dogs were able to pick the angry or happy face by touching a picture of it with their noses more often than one would expect by random chance.

The study showed the animals had figured out how to apply what they learned about human faces during training to new faces in the testing stage. "We can rule out that the dogs simply distinguish between the pictures based on a simple cue, such as the sight of teeth," said study author Corsin Muller. "Instead, our results suggest that the successful dogs realized that a smiling mouth means the same thing as smiling eyes, and the same rule applies to an angry mouth having the same meaning as angry eyes.”

"With our study, we think we can now confidently conclude that at least some dogs can distinguish human facial expressions," Muller told Live Science.

At this point, it is not clear why dogs seem to be equipped with the ability to recognize different facial expressions in humans. "To us, the most likely explanation appears to be that the basis lies in their living with humans, which gives them a lot of exposure to human facial expressions," and this exposure has provided them with many chances to learn to distinguish between them, Muller said.

Like most of us, I try to be mindful of food that goes to waste. The arugula (芝麻菜) was to make a nice green salad, rounding out a roast chicken dinner. But I ended up working late. Then friends called with a dinner invitation. I stuck the chicken in the freezer. But as days passed, the arugula went bad. Even worse, I had unthinkingly bought way too much; I could have made six salads with what I threw out.

In a world where nearly 800 million people a year go hungry, "food waste goes against the moral grain," as Elizabeth Royte writes in this month's cover story. It's jaw-dropping how much perfectly good food is thrown away — from "ugly" (but quite cat able) vegetables rejected by grocers to large amounts of uneaten dishes thrown into restaurant garbage cans.

Producing food that no one eats wastes the water, fuel, and other resources used to grow it. That makes food waste an environmental problem. In fact, Royte writes," if food waste were a country, it would be the third largest producer of greenhouse gases in the world. "

If that's hard to understand, let's keep it as simple as the arugula at the back of my refrigerator. Mike Curtin sees my arugula story all the time — but for him, it's more like 12 boxes of donated strawberries nearing their last days. Curtin is CEO of DC Central Kitchen in Washington. D.C., which recovers food and turns it into healthy meals. Last year it recovered more than 807, 500 pounds of food by taking donations and collecting blemished (有瑕疵的) produce that otherwise would have rotted infields. And the strawberries? Volunteers will wash, cut, and freeze or dry them for use in meals down the road.

Such methods seem obvious, yet so often we just don't think. "Everyone can play a part in reducing waste, whether by not purchasing more food than necessary in your weekly shopping or by asking restaurants to not include the side dish you won't eat." Curtin says.

Sometime in the early 1960s, a significant thing happened in Sydney, Australia. The city discovered its harbor. Then, one after another, Sydney discovered tots of things that were just sort of there-broad parks, superb beaches, and a culturally diverse population. But it is the harbor that makes the city.

Andrew Reynolds, a cheerful fellow in his early 30s, pilots Sydney ferryboats for a living. I spent the whole morning shuttling back and forth across the harbor. After our third run Andrew shut down the engine, and we went our separate ways-he for a lunch break, I to explore the city.

"I'll miss these old boats," he said as we parted.

"How do you mean?" I asked.

"Oh, they're replacing them with catamarans. Catamarans are faster, but they're not so elegant, and they're not fun to pilot. Hut that's progress, I guess."

Everywhere in Sydney these days, change and progress are the watchwords（口号）, and traditions are increasingly rare. Shirley Fitzgerald, the city's official historian, told me that in its rush to modernity in the 1970s, Sydney swept aside much of its past, including many of its finest buildings. "Sydney is confused about itself," she said. "We can't seem to make up our minds whether we want a modern city or a traditional one. It's a conflict that we aren't getting any better at resolving（解决）.”

On the other hand, being young and old at the same time has its attractions. I considered this when I met a thoughtful young businessman named Anthony. "Many people say that we lack culture in this country," he told me. "What people forget is that the Italians, when they came to Australia, brought 2000 years of their culture, the Greeks some 3000 years, and the Chinese more still. We've got a foundation built on ancient cultures but with a drive and dynamism of a young country. It's a pretty hard combination to beat."

He is right, but I can't help wishing they would keep those old ferries.