1 . Returning to a book you’ve read many times can feel like drinks with an old friend. There’s a welcome familiarity - but also sometimes a slight suspicion that time has changed you both, and thus the relationship. But books don’t change, people do. And that’s what makes the act of rereading so rich and transformative.

The beauty of rereading lies in the idea that our bond with the work is based on our present mental register. It’s true, the older I get, the more I feel time has wings. But with reading, it’s all about the present. It’s about the now and what one contributes to the now, because reading is a give and take between author and reader. Each has to pull their own weight.

There are three books I reread annually .The first, which I take to reading every spring is Emest Hemningway’s A Moveable Feast. Published in 1964, it’s his classic memoir of 1920s Paris. The language is almost intoxicating (令人陶醉的)，an aging writer looking back on an ambitious yet simpler time. Another is Annie Dillard’s Holy the Firm, her poetic 1975 ramble (随笔) about everything and nothing. The third book is Julio Cortazar’s Save Twilight: Selected Poems, because poetry. And because Cortazar.

While I tend to buy a lot of books, these three were given to me as gifs, which might add to the meaning I attach to them. But I imagine that, while money is indeed wonderful and necessary, rereading an author’s work is the highest currency a reader can pay them. The best books are the ones that open further as time passes. But remember, it’s you that has to grow and read and reread in order to better understand your friends.

2 . According to a recent study in the Journal of Consumer Research, both the size and consumption habits of our eating companions can influence our food intake. And contrary to existing research that says you should avoid eating with heavier people who order large portions(份), it's the beanpoles with big appetites you really need to avoid.

To test the effect of social influence on eating habits, the researchers conducted two experiments. In the first, 95 undergraduate women were individually invited into a lab to ostensibly(表面上)participate in a study about movie viewership. Before the film began, each woman was asked to help herself to a snack. An actor hired by the researchers grabbed her food first. In her natural state, the actor weighed 105 pounds. But in half the cases she wore a specially designed fat suit which increased her weight to 180 pounds.

Both the fat and thin versions of the actor took a large amount of food. The participants followed suit, taking more food than they normally would have. However, they took significantly more when the actor was thin.

For the second test, in one case the thin actor took two pieces of candy from the snack bowls. In the other case, she took 30 pieces. The results were similar to the first test: the participants followed suit but took significantly more candy when the thin actor took 30 pieces.

The tests show that the social environment is extremely influential when we're making decisions. If this fellow participant is going to eat more, so will I. Call it the “I’ll have what she's having” effect. However, we'll adjust the influence. If an overweight person is having a large portion, I'll hold back a bit because I see the results of his eating habits. But if a thin person eats a lot, I'll follow suit. If he can eat much and keep slim, why can't I?

3 . When you were trying to figure out what to buy for the environmentalist on your holiday list, fur probably didn’t cross your mind. But some ecologists and fashion (时装)enthusiasts are trying to bring back the market for fur made from nutria(海狸鼠).

Unusual fashion shows in New Orleans and Brooklyn have showcased nutria fur made into clothes in different styles. “It sounds crazy to talk about guilt-free fur-unless you understand that the nutria are destroying vast wetlands every year”, says Cree McCree, project director of Righteous Fur.

Scientists in Louisiana were so concerned that they decided to pay hunters $5 a tail. Some of the fur ends up in the fashion shows like the one in Brooklyn last month.

Nutria were brought there from Argentina by fur farmers and let go into the wild. “The ecosystem down there can’t handle this non-native species(物种).It’s destroying the environment. It’s them or us.” says Michael Massimi, an expert in this field.

The fur trade kept nutria in check for decades，but when the market for nutria collapsed in the late 1980s，the cat-sized animals multiplied like crazy.

Biologist Edmond Mouton runs the nutria control program for Louisiana. He says it’s not easy to convince people that nutria fur is green, but he has no doubt about it. Hunters bring in more than 300,000 nutria tails a year, so part of Mouton’s job these days is trying to promote fur.

Then there’s Righteous Fur and its unusual fashion. Model Paige Morgan says，”To give people a guilt-free option that they can wear without someone throwing paint on them-I think that’s going to be a massive thing, at least here in New York.” Designer Jennifer Anderson admits it took her a while to come around to the opinion that using nutria fur for her creations is morally acceptable. She is trying to come up with a label to attach to nutria fashions to show it is eco-friendly.

4 . For those who can stomach it, working out before breakfast may be more beneficial for health than eating first, according to a study of meal timing and physical activity.

Athletes and scientists have long known that meal timing affects performance. However, far less has been known about how meal timing and exercise might affect general health.

To find out, British scientists conducted a study. They first found 10 overweight and inactive but otherwise healthy young men, whose lifestyles are, for better and worse, representative of those of most of us. They tested the men’s fitness and resting metabolic (新陈代谢的) rates and took samples (样品) of their blood and fat tissue.

Then, on two separate morning visits to the scientists’ lab, each man walked for an hour at an average speed that, in theory, should allow his body to rely mainly on fat for fuel. Before one of these workouts, the men skipped breakfast, meaning that they exercised on a completely empty stomach after a long overnight fast (禁食). On the other occasion, they ate a rich morning meal about two hours before they started walking.

Just before and an hour after each workout, the scientists took additional samples of the men’s blood and fat tissue.

Then they compared the samples. There were considerable differences. Most obviously, the men displayed lower blood sugar levels at the start of their workouts when they had skipped breakfast than when they had eaten. As a result, they burned more fat during walks on an empty stomach than when they had eaten first. On the other hand, they burned slightly more calories (卡路里), on average, during the workout after breakfast than after fasting.

But it was the effects deep within the fat cells that may have been the most significant, the researchers found. Multiple genes behaved differently, depending on whether someone had eaten or not before walking. Many of these genes produce proteins (蛋白质) that can improve blood sugar regulation and insulin (胰岛素) levels throughout the body and so are associated with improved metabolic health. These genes were much more active when the men had fasted before exercise than when they had breakfasted.

The implication of these results is that to gain the greatest health benefits from exercise, it may be wise to skip eating first.

7 . There is more that comes with older age than greying hair and wrinkled skin When humans reach their later years, they favour more established friends and their social circle is reduced.

Now, for what appears to be the first time, scientists have seen the same behaviour in another species. Twenty years of observations of chimpanzees (猩猩) reveal that older males choose to hang out with their long-term friends at the expense of other relationships.

The researchers studied 78, 000 hours of observations made between 1996 and 2016 that followed the social interactions of 21 male chimpanzees between the ages of 15 and 58 years old. They classified the chimps’ relationships depending on the amount of time they sat with others and groomed (梳毛) them. They then rated the various pairings as mutual (相互的) friendships, where both chimps seemed to enjoy the relationship; one-sided friendships, where one chimp was more keen to be friends than the other; and non-friendships, where neither chimp showed interest in the other.

When the scientists looked at the patterns of friendships, they found that the older chimps had more mutual friendships and fewer one-sided friendships than younger chimps. Another feature seen in older humans was also spotted in the chimps. As the males got older, their levels of aggression (挑衅) tailed off, meaning they started fewer fights and tended to intimidate others in their group less often.

The observations have left the researchers puzzled. According to an idea in psychology known as socioemotional selectivity theory, or SST, older humans prefer more positive relationships because they are aware time is running out. But many animal experts argue that chimpanzees lack the human sense of mortality (死亡), suggesting something else is driving the behaviour.

Robin Dunbar, a professor of evolutionary psychology at the University of Oxford, said in humans, the decline in social circles with age is due to declining social motivation to get out and meet people combined by lack of opportunity. In chimpanzees, as older males compete less for mates, they may focus on close, reciprocal (互惠的) relationships with trusted partners, she said.

8 . Bitcoin and other so-called cryptocurrencies （加密货币）have been all over the news lately. Apparently, the idea of money that's not tied to a specific bank—or a specific country—is appealing to many. But it's worth remembering that the banking system that we now all live with is just that： A modern invention. Not so long ago, money was almost always created and used locally, and bartering was common. （In fact, it still is common among many online local networks, like the Buy Nothing Project.）.

In the past, money's makeup varied from place to place, depending on what was considered valuable there. So while some of the world's first coins were made from a naturally occurring hybrid of gold and silver called electrum （银金矿），objects other than coins have served as currency, including beads, ivory, livestock, and cowrie shells. In West Africa, bracelets of bronze or copper were used as cash, especially if the transaction was associated with the slave trade there. Throughout the colonial period, tobacco was used to replace coins or paper bills in Virginia, Maryland and North Carolina, even though it was used elsewhere in the colonies and extensively throughout Europe and the U. K.

Today, on an island in the Pacific, a specific type of shell still serves as currency—and some people there are even hoarding（贮存）it, just like Bitcoin moguls, convinced that one day, it will make them wealthy beyond imagination. On Malaita, the most-populated island that's part of the Solomon Islands, shells are accepted at most places in exchange for goods.

"How much tuna（金枪鱼）you can get for your shells depends on their color and shape," Mary Bruno, a shop owner from the small town of Auki, on Malaita, told Vice. "One strip of darker shells might get you about two cans of smaller tuna, but the red ones are worth more. For the red ones, one strip might get enough tuna to feed a big family for a long time."

Just like a mint that creates coins, there's only one place on the island where the shells, which are polished and strung together to form 3-foot-long ropes, are made. The strips of red, white, and black shells all come from Langa Langa Lagoon, where artificial islands were long-ago built by locals to escape from the island-dwelling cannibals. Once marooned（困住）out on their islands, locals needed a currency to use among themselves, and so the shell currency was born.

Using shells for money was common throughout the Pacific islands as late as the early 1900s, but Malaita is unique in that they are still used today. And just like cryptocurrencies, there are those who think the islanders are smart to invest in this type of money, which is reported to have risen in value over the last three decades. It might seem strange to hoard a bunch of processed, strung-together shells, but what is a pile of dollars? Just a specially printed piece of paper and hemp that we've assigned value to—and probably less durable over time than those shells.

10 . We recognize our friends’ faces. And we’re not alone. Many social animals can identify individuals of their own species by features of their faces. That's important, because they need to be able to change their behavior depending on who they meet. And a recent research has shown that some species of monkeys, birds, and domesticated (家养的) animals can even tell different faces apart by looking at photographs alone.

Ethologist Léa Lansade of the French National Research Institute for Agriculture, Food and Environment did an experiment to find out how well horses can recognize individual people in photographs.

She and her team first taught the horses how to “choose” between two side-by-side pictures by touching their noses to a computer screen. The horses were then shown photos of their present keeper alongside faces of unfamiliar humans. They had never seen photos of any of the people before. The horses correctly identified their current keeper and ignored (忽视) the stranger’s face about 75%of the time. In fact, even though the horses didn't get it right every single time, they were at least as correct in picking out their earlier keeper as they were at identifying their present one.

The results suggest that not only can horses differentiate between familiar and unfamiliar human faces, they also naturally understand that photographs are two dimensional representations (二维呈现) of real life, without any other intimations such as smell or sound. And they’re even better at this than our oldest animal parter, the domestic dog.

In addition, horses seem to have a strong long-term memory for human faces, like their long lifespan and history of domestication. In future experiments, the researchers would like to test whether looking at photos of people that they have had bad experiences with in the past might cause horses to act anxious or even avoidance. So maybe think twice before doing anything that might give a horse a long face.