【推荐3】If someone is crying in an attempt to fake sorrow, we say they are shedding “crocodile tears”. But how and why did we start relating insincere displays of feelings to crocodiles?

The origin may have become popular around the 14th century when a bestseller, The Voyage and Travel of Sir John Mandeville, referenced a kind of snake who drops tears while eating their human victims.

In the centuries since, crying crocodiles have been related to fake sorrow. The expression has been used as a story to teach sincere regret, by Shakespeare and, more recently, by media mocking tearful politicians or murder suspects.

In 2007, University of Florida zoologist Kent Vliet actually proved that the animals do drop tears while snacking. But because crocodiles eat while in the water—making a study of their meal-time tears difficult—he studied their close relatives, alligators, who might dine on dry land. Out of the seven he filmed eating at a Florida alligator park, five teared up before, during, and after eating.

Vliet’s theory is that when the animals enthusiastically hit their jaws, the movement forces air through the crocodiles’ sinuses and finally empties tears into their eyes. Their eyes not only water but can bubble, as Vliet witnessed at the alligator park, where some even teared up in expectation of their meal of chicks and other food.

Vliet was asked to investigate the biology behind this phenomenon by Malcolm Shaner, a doctor, about why facial palsy sufferers cry when they chew. Findings suggest that this is similar to the case of crocodiles.

【推荐1】Andean Condors(秃鹰），weighing up to 13 kilograms with a 10-foot wingspan, are one of the world's heaviest and largest flying birds. Spending their days circling the Andes mountains and nearby Pacific coasts in search of food, they manage to stay afloat (悬浮） for hours.

Though researchers have long suspected that the massive creatures conserved energy by using rising air currents to surf the skies, nobody had ever documented how infrequently the birds used their wings afloat. Now, a new study has found that the incredibly energy-efficient condors use their wings just 1 percent of their time - mostly during takeoff and landing.

The extensive research, conducted in Patagonia from 2013 to 2018, involved attaching high-tech flight recorders to the birds' 'wings. The collected information was too much to send back via the phone or satellite network. Hence, the researchers had to physically take back the devices, which were designed to fall off the birds after a week. While a GPS tracker allowed the scientists to confirm the recorders' exact locations, getting to them was no easy task given Patagonia's rough surface features.

After losing seven recorders for every one they took back,the team shifted their focus to younger condors, who tend to fly over gently rolling hills rather than the mountain tops frequented by adults. The 250 hours of collected flight data revealed that the birds flew for an average of three hours but flapped(拍打）their wings for less than two minutes of the time.

One efficient pilot managed to cover 172 kilometers over five hours without a single flap! The researchers say the large fliers consume the most energy during takeoff. However, once in the air, they can fly for long periods of time without turning on their “engines". The scientists suppose that adult condors may demonstrate an even more impressive flight record than the younger.

【推荐2】Any foreigner who has tried to learn Chinese can tell how hard it is to master the tones required to speak and understand. And anyone who has tried to learn to play the violin or other instruments can report similar challenges.

Now researchers have found that people with musical training have an easier time learning Chinese. Writing in the online edition of Nature Neuroscience, researchers from Northwestern University say that both skills draw on the same parts of the brain that help people discover changes in pitch(音高).

One of the study's authors, Nina Kraus, said the findings suggested that studying music ''actually tunes our sensory system''. This means that schools that want children to do well in languages should hesitate before cutting music programs, Dr. Kraus said. She said music training might also help children with language problems.

Mandarin(普通话)speakers have been shown to have a more complex encoding(编码) of pitch patterns in their brains than English speakers do. This is because in Mandarin and other Asian languages, pitch plays a central role. A single-syllable word can have several meanings depending on how it is intoned.

For this study, the researchers looked at 20 non-Chinese speaking volunteers, half with no musical background and half who have studied an instrument for at least six years.

As they were shown a movie, the volunteers also heard an audio tape of the Mandarin word ''mi'' in three of its meanings: squint, bewilder and rice. The researchers recorded activities in their brain stems to see how well they were processing the sounds. Those with a music background showed much more brain activities in response to the Chinese sounds.

The lead author of the study, Patrick C. M. Wong, said it might work both ways. It appears that native speakers of tonal languages may do better at learning instruments.

【推荐3】Scientists have already studied how dogs respond to people’s behavior and speech. But researchers are just scratching the surface of human-cat interactions. House cats do appear to respond to the expressions on people’s faces. Cats can also tell different human voices. But can cats recognize their own names?

Saito, a psychologist at Sophia University in Tokyo, and her colleagues decided to find the answer. They asked the owners of 77 cats to say four nouns of similar length followed by the cat’s name. Cats gradually lost interest in each random(随机的) noun. But when the owner said a cat’s name, the cats reacted strongly. They moved their ears, head or tail, changed their back paw’s position. And, of course, they miaowed.

These findings mean that cats join the ranks of animals that have shown some sort of response in experiments to the names people give them. Those animals include dogs, dolphins, apes and parrots. It’s hard to compare the number of words across species, though. Some dogs, for example, can tell the difference between hundreds of human words.

The study makes a strong case that cats are perfectly capable of recognizing their own names. Getting a treat or hug as a reward is part of how cats learn to recognize a name. However, owners may also use their cat’s name in a negative setting, like yelling at Fluffy to get off the stove. As a result, cats can probably learn to associate these familiar utterances with good and bad experiences, Saito notes. And that might not be great for human-cat relations. So only using a cat’s name in a positive context and using a different term in a negative context could help cats and humans communicate more clearly.

So cats may recognize their names. But will they come when called? Don’t get your hopes up.

【推荐1】Amazon has announced that it has added features to its Alexa voice assistant that can help users determine their risk level for having got the COVID-19 coronavirus (新型冠状病毒). As of now all Alexa users in the United States can ask Alexa questions like, “Alexa, what do I do if I think I have COVID-19?” or “Alexa, what do I do if I think I have coronavirus?” upon which Alexa will begin triaging (检验分类) them.

Once one of the above questions is asked, Alexa will ask the user about their symptoms, travel history, and any possible exposure they may have had to someone infected with the disease. Depending upon the user’s response, Alexa will offer the user guidance that comes directly from the Centers for Disease Control and Prevention about what they should do next.

Another cool feature added to Alexa is the ability to ask the personal assistant to sing a song for 20 seconds while you wash your hands. Twenty seconds is the minimum washing time with soap and water people need to perform on their hands in order to destroy traces of the virus they may have picked up.

Users can take advantage of Alexa’s new COVID-19 features on any device Alexa runs on, including smartphones, tablets, Kindles, and more. It should also be noted that Amazon isn’t the first to empower its voice assistant to offer CDC COVID-19 information. Earlier this week Apple pushed an update out to Siri that allows users to ask, “Hey Siri, do I have the coronavirus?” and get advice based on CDC information.

【推荐2】Have you ever wondered why certain pop songs just make you feel so good?

Researchers studying the question found that the right combination of uncertainty and surprise is what gives listeners the most pleasure.

The study, published in the journal Current Biology, involved an analysis of 80,000 chords( 和弦)in 745 pop songs from the US Billboard “Hot 100” chart between 1958 and 1991.

The researchers - from institutes in Germany, Norway, Denmark and the UK - used a machine-learning model to quantify the level of uncertainty and surprise of these chords, and then asked 39 adult volunteers to rate how pleasurable they found each series of chords.

Each song was stripped of its melody and lyrics(歌词)so that only chord progressions were left and the results couldn’t be influenced by other associations to the songs that listeners might have had.

They found two things: that participants got greater pleasure when they were relatively certain what would happen next but then were surprised by an unexpected chord progression. However, the same number of participants found it pleasant when they were uncertain as to what would follow, and then the subsequent chords were more familiar to them.

“It is fascinating that humans can get pleasure from a piece of music just by how sounds are ordered over time,” Vincent Cheung, the lead researcher on the paper from the Max Planck Institute for Human Cognitive and Brain Sciences, Germany, said in a statement.

“Songs that we find pleasant are likely those which strike a good balance between knowing what is going to happen next and surprising us with something we did not expect. Understanding how music activates our pleasure system in the brain could explain why listening to music might help us feel better when we are feeling blue.”

Cheung told CNN that pleasure in music has a lot to do with what listeners expect. Previous studies had looked into the effects of surprise on pleasure, but he and his colleagues’ study also focused on the uncertainty of listeners’ predictions.

The findings may help improve artificial musical algorithms(算法)and could help composers write music or predict musical trends.

“The idea is that hopefully as a scientist analyzing these patterns of pleasure in humans, you can somehow work out where music can go next,” Peter Harrison, a researcher at Queen Mary University, London, who worked on the project, told CNN.

As part of the same experiment, the researchers also used brain imaging to locate the areas of the brain reflected in musical pleasure. They found the regions involved were the amygdala, the hippocampus and the auditory cortex, which process emotions, learning and memory, and sound, respectively.

Cheung added that another part of the brain, the nucleus accumbens - which processes reward expectations - was perhaps responsible for “directing our attention towards the music so that we will try to find out what will happen next.”