Chapter 6. Evolution of the Brain and Behavior
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By Gareth Cook What are the most intelligent creatures on the planet? Humans come first. (Though there are days when we have to wonder.) After Homo sapiens, most people might answer chimpanzees, and then maybe dogs and dolphins. But what of birds? The science writer Jennifer Ackerman offers a lyrical testimony to the wonders of avian intelligence in her new book, “The Genius of Birds.” There have long been hints of bird smarts, but it’s become an active field of scientific inquiry, and Ackerman serves as tour guide. She answered questions from Mind Matters editor Gareth Cook. What drew you to birds? I’ve watched birds for most of my life. I admire all the usual things about them. Their plumage and song. Their intense way of living. Their flight. I also admire their resourcefulness and pluck. I’ve always been intrigued by their apparently smart behavior, whether learned or innate. I grew up in Washington, D.C. — the second youngest in a gaggle of five girls. My parents had precious little time for one-on-one. Especially my dad, who had a demanding government job. So when he asked me if I wanted to go birdwatching with him one spring morning when I was seven or eight, I jumped at the chance. It was magical, going out in the dark woods along the C&O canal and listening for bird song. My father had learned his calls and songs in Boy Scout camp from an expert, an elderly Greek man named Apollo, so he was pretty good at identifying birds, even the shy woodland species. Eventually he gave me my own copy of Peterson’s Field Guide, along with a small pair of binoculars. I’ve loved birds ever since. My first run in with a clever bird was on our dining room table. We had a pet parakeet, a budgerigar named Gre-Gre, who was allowed to fly around the dining room and perch on our head or shoulders. He had a kind of social genius. He made you love him. But at breakfast, it was impossible to eat your cereal without his constant harassment. He liked to perch on the edge of my bowl and peck at the cereal, flapping his wings frantically to keep his balance, splashing my milk. I’d build a barricade of boxes around my place setting, but he always found a way in, moving a box or popping over the top. He was a good problem-solver. © 2016 Scientific American
By Virginia Morell Moths have an almost fatal attraction to lights—so much so that we say people are drawn to bad ends “like moths to a flame.” But in this age of global light pollution, that saying has a new poignancy: Moths, which are typically nocturnal insects, are dying in droves at artificial lights. The high levels of mortality should have evolutionary consequences, leading to moths that avoid lights, biologists say. To find out, two scientists tested the flight-to-light behavior of 1048 adult ermine moths (Yponomeuta cagnagella, shown above) in Europe. The researchers collected the insects in 2007 as larvae that had just completed their first molt. Three hundred and twenty came from populations that lived where the skies were largely dark; 728 were gathered in light polluted areas. They were raised in a lab with 16 hours of daylight and 8 hours of darkness daily while they completed their life stages. Two to 3 days after emerging as moths, they were released in a flight cage with a fluorescent tube at one side. Moths from high light pollution areas were significantly less attracted to the light than those from the darker zones, the scientists report in today’s issue of Biology Letters. Overall, moths from the light-polluted populations had a 30% reduction in the flight-to-light behavior, indicating that this species is evolving, as predicted, to stay away from artificial lights. That change should increase these city moths’ reproductive success. But their success comes at a cost: To avoid the lights, the moths are likely flying less, say the scientists, so they aren’t pollinating as many flowers or feeding as many spiders and bats. © 2016 American Association for the Advancement of Science.
Link ID: 22100 - Posted: 04.13.2016
By FRANS de WAAL TICKLING a juvenile chimpanzee is a lot like tickling a child. The ape has the same sensitive spots: under the armpits, on the side, in the belly. He opens his mouth wide, lips relaxed, panting audibly in the same “huh-huh-huh” rhythm of inhalation and exhalation as human laughter. The similarity makes it hard not to giggle yourself. The ape also shows the same ambivalence as a child. He pushes your tickling fingers away and tries to escape, but as soon as you stop he comes back for more, putting his belly right in front of you. At this point, you need only to point to a tickling spot, not even touching it, and he will throw another fit of laughter. Laughter? Now wait a minute! A real scientist should avoid any and all anthropomorphism, which is why hard-nosed colleagues often ask us to change our terminology. Why not call the ape’s reaction something neutral, like, say, vocalized panting? That way we avoid confusion between the human and the animal. The term anthropomorphism, which means “human form,” comes from the Greek philosopher Xenophanes, who protested in the fifth century B.C. against Homer’s poetry because it described the gods as though they looked human. Xenophanes mocked this assumption, reportedly saying that if horses had hands they would “draw their gods like horses.” Nowadays the term has a broader meaning. It is typically used to censure the attribution of humanlike traits and experiences to other species. Animals don’t have “sex,” but engage in breeding behavior. They don’t have “friends,” but favorite affiliation partners. Given how partial our species is to intellectual distinctions, we apply such linguistic castrations even more vigorously in the cognitive domain. By explaining the smartness of animals either as a product of instinct or simple learning, we have kept human cognition on its pedestal under the guise of being scientific. Everything boiled down to genes and reinforcement. To think otherwise opened you up to ridicule, which is what happened to Wolfgang Köhler, the German psychologist who, a century ago, was the first to demonstrate flashes of insight in chimpanzees. © 2016 The New York Times Company
Modern humans diverged from Neanderthals some 600,000 years ago – and a new study shows the Y chromosome might be what kept the two species separate. It seems we were genetically incompatible with our ancient relatives – and male fetuses conceived through sex with Neanderthal males would have miscarried. We knew that some cross-breeding between us and Neanderthals happened more recently – around 100,000 to 60,000 years ago. Neanderthal genes have been found in our genomes, on X chromosomes, and have been linked to traits such as skin colour, fertility and even depression and addiction. Now, an analysis of a Y chromosome from a 49,000-year-old male Neanderthal found in El Sidrón, Spain, suggests the chromosome has gone extinct seemingly without leaving any trace in modern humans. This could simply be because it drifted out of the human gene pool or, as the new study suggests, it could be because genetic differences meant that hybrid offspring who had this chromosome were infertile – a genetic dead end. Fernando Mendez of Stanford University, and his colleagues compared the Neanderthal Y chromosome with that of chimps, and ancient and modern humans. They found mutations in four genes that could have prevented the passage of Y chromosome down the paternal line to the hybrid children. “Some of these mutations could have played a role in the loss of Neanderthal Y chromosomes in human populations,” says Mendez. © Copyright Reed Business Information Ltd.
by Daniel Galef Footage from a revolutionary behavioural experiment showed non-primates making and using tools just like humans. In the video, a crow is trying to get food out of a narrow vessel, but its beak is too short for it to reach through the container. Nearby, the researchers placed a straight wire, which the crow bent against a nearby surface into a hook. Then, holding the hook in its beak, it fished the food from the bottle. Corvids—the family of birds that includes crows, ravens, rooks, jackdaws, and jays—are pretty smart overall. Although not to the level of parrots and cockatoos, ravens can also mimic human speech. They also have a highly developed system of communication and are believed to be among the most intelligent non-primate animals in existence. McGill Professor Andrew Reisner recalls meeting a graduate student studying corvid intelligence at Oxford University when these results were first published in 2015. “I had read early in the year that some crows had been observed making tools, and I mentioned this to him,” Reisner explained. “He said that he knew about that, as it had been he who had first observed it happening. Evidently the graduate students took turns watching the ‘bird box,’ […] and the tool making first occurred there on his shift.”
Philip Ball James Frazer’s classic anthropological study The Golden Bough1 contains a harrowing chapter on human sacrifice in rituals of crop fertility and harvest among historical cultures around the world. Frazer describes sacrificial victims being crushed under huge toppling stones, slow-roasted over fires and dismembered alive. Frazer’s methods of analysis wouldn't all pass muster among anthropologists today (his work was first published in 1890), but it is hard not to conclude from his descriptions that what industrialized societies today would regard as the most extreme psychopathy has in the past been seen as normal — and indeed sacred — behaviour. In almost all societies, killing within a tribe or clan has been strongly taboo; exemption is granted only to those with great authority. Anthropologists have suspected that ritual human sacrifice serves to cement power structures — that is, it signifies who sits at the top of the social hierarchy. The idea makes intuitive sense, but until now there has been no clear evidence to support it. In a study published in Nature2, Joseph Watts, a specialist in cultural evolution at the University of Auckland in New Zealand, and his colleagues have analysed 93 traditional cultures in Austronesia (the region that loosely embraces the many small and island states in the Pacific and Indonesia) as they were before they were influenced by colonization and major world religions (generally in the late 19th and early 20th centuries). © 2016 Nature Publishing Group
Ewen Callaway Homo floresiensis, the mysterious and diminutive species found in Indonesia in 2003, is tens of thousands of years older than originally thought — and may have been driven to extinction by modern humans. After researchers discovered H. floresiensis, which they nicknamed the hobbit, in Liang Bua cave on the island of Flores, they concluded that its skeletal remains were as young as 11,000 years old. But later excavations that have dated more rock and sediment around the remains now suggest that hobbits were gone from the cave by 50,000 years ago, according to a study published in Nature on 30 March1. That is around the time that modern humans moved through southeast Asia and Australia. “I can’t believe that it is purely coincidence, based on what else we know happens when modern humans enter a new area,” says Richard Roberts, a geochronologist at the University of Wollongong, Australia. He notes that Neanderthals vanished soon after early modern humans arrived in Europe from Africa. Roberts co-led the study with archaeologist colleague Thomas Sutikna (who also helped coordinate the 2003 dig), and Matthew Tocheri, a paleoanthropologist at Lakehead University in Thunder Bay, Canada. The first hobbit fossil, known as LB1, was found in 20032 beneath about 6 metres of dirt and rock. Its fragile bones were too precious for radiocarbon dating, so the team collected nearby charcoal, on the assumption that it had accrued at the same time as the bones. That charcoal was as young as 11,000 years old, researchers reported at the time3, 4. “Somehow these tiny people had survived on this island 30,000 years after modern humans arrived,” says Roberts. “We were scratching our heads. It couldn’t add up.” © 2016 Nature Publishing Group,
Link ID: 22055 - Posted: 03.31.2016
by Sarah Zielinski There must be something wrong with the guy who never leaves home, right? Maybe not — at least if that guy is a male spotted hyena. Males that stay with their birth clan, instead of taking off to join a new group, may simply be making a good choice, a new study suggests. Spotted hyenas are a matriarchal society. Females are in charge. They rank higher than every male in the clan. And the females generally stay with the clan for their entire lives. But males face a choice when they reach two and a half years in age. They can stay with the clan, or they can leave and join a new clan. Each choice has its pros and cons. Staying with the clan means that a male hyena keeps a place at the top of the male pecking order. He’ll probably have his mother around to help. But he’ll be limited in the number of females he can mate with, because many of the female hyenas won’t mate with him because they might be related. If he joins a new clan, the male hyena might have access to more females — and they might even be better than the ones in his home clan — but he’ll start with the lowest social rank and have to spend years fighting his way to the top. Among most group-living mammal species, the guys that stay at home turn out to be losers, siring fewer offspring. But spotted hyenas, it appears, are an exception. Eve Davidian of the Leibniz Institute for Zoo and Wildlife Research in Berlin and colleagues tracked 254 male spotted hyenas that lived in eight clans in Ngorongoro Crater in Tanzania throughout their lives, a study lasting 20 years. When these males reached the age of maturity, they left their clans to take a look at the other options available to them. Forty-one hyenas returned to their home clans, and 213 settled with new ones. © Society for Science & the Public 2000 - 2016
By Catherine Matacic Twenty-three years ago, a bonobo named Kanzi (above) aced a test in understanding human language. But a new study reveals he may not be as brainy as scientists thought—at least when it comes to grammar. The original test consisted of 660 verbal commands, in English, that asked Kanzi to do things like "show me the hot water" and "pour cold water in the potty." Overall, the ape did well, responding correctly 71.5% of the time (compared with 66.6% for an infant human). But when the researchers asked him to perform an action on more than one item, his performance plummeted to just 22.2%, according to the new analysis. When he was asked to "give the lighter and the shoe to Rose," for example, he gave Rose the lighter, but no shoe. When asked to "give the water and the doggie to Rose," he gave her the toy dog, but no water. The cause? Animals like bonobos may have a harder time than humans in processing complex noun phrases like “water and doggie,” linguist Robert Truswell of the University of Edinburgh reported in New Orleans, Louisiana, this week at the Evolution of Language conference. This feature of grammar—which effectively “nests” one unit within the bigger construct of a sentence—is easily picked up by humans, allowing us to communicate—and understand—more complex ideas. But Truswell cautions that humans probably aren’t born with the ability to interpret this kind of nesting structure. Instead, we must be taught how to use it. © 2016 American Association for the Advancement of Science
By NATALIE ANGIER Juan F. Masello never intended to study wild parrots. Twenty years ago, as a graduate student visiting the northernmost province of Patagonia in Argentina, he planned to write his dissertation on colony formation among seabirds. But when he asked around for flocks of, say, cormorants or storm petrels, a park warden told him he was out of luck. “He said, ‘This is the only part of Patagonia with no seabird colonies,’” recalled Dr. Masello, a principal investigator in animal ecology and systematics at Justus Liebig University in Germany. Might the young scientist be interested in seeing a large colony of parrots instead? The sight that greeted Dr. Masello was “amazing” and “incredible,” he said. “It was almost beyond words.” On a 160-foot-high sandstone cliff that stretched some seven miles along the Atlantic coast, tens of thousands of pairs of burrowing parrots had used their powerful bills to dig holes — their nests — deep into the rock face. And when breeding season began not long afterward, the sky around the cliffs erupted into a raucous carnival of parrot: 150,000 crow-size, polychromed aeronauts with olive backsides, turquoise wings, white epaulets and bright red belly patches ringed in gold. Dr. Masello was hooked. Today, Dr. Masello’s hands are covered with bite scars. He has had four operations to repair a broken knee, a broken nose — “the little accidents you get from working with parrots,” he said. Still, he has no regrets. “Their astonishing beauty and intelligence,” Dr. Masello said, “are inspirational.” © 2016 The New York Times Company
Giant manta rays have been filmed checking out their reflections in a way that suggests they are self-aware. Only a small number of animals, mostly primates, have passed the mirror test, widely used as a tentative test of self-awareness. “This new discovery is incredibly important,” says Marc Bekoff, of the University of Colorado in Boulder. “It shows that we really need to expand the range of animals we study.” But not everyone is convinced that the new study proves conclusively that manta rays, which have the largest brains of any fish, can do this – or indeed, that the mirror test itself is an appropriate measure of self-awareness. Csilla Ari, of the University of South Florida in Tampa, filmed two giant manta rays in a tank, with and without a mirror inside.The fish changed their behaviour in a way that suggested that they recognised the reflections as themselves as opposed to another manta ray. They did not show signs of social interaction with the image, which is what you would expect if they perceived it to be another individual. Instead, the rays repeatedly moved their fins and circled in front of the mirror (click on image below to see one in action). This suggests they could see whether their reflection moved when they moved. The frequency of these movements was much higher when the mirror was in the tank than when it was not. manta © Copyright Reed Business Information Ltd.
By Manuel Valdes For nearly every step of his almost 12-mile walks around Seattle, Darryl Dyer has company. Flocks of crows follow him, signaling each other, because they all know that he’s the guy with the peanuts. “They know your body type. The way you walk,” Dyer said. “They’ll take their young down and say: ‘You want to get to know this guy. He’s got the food.’ ” Scientists have known for years that crows have great memories, that they can recognize a human face and behavior, that they can pass that information on to their offspring. Researchers are trying to understand more about the crow’s brain and behavior, specifically what the birds do when they see one of their own dead. They react loudly, but the reasons aren’t entirely known. Among the guesses is that they are mourning; given that crows mate for life, losing a partner could be a significant moment for the social animals. There are anecdotes of crows placing sticks and other objects on dead birds — a funeral of sorts. Using masks with dark-haired wigs that looked creepily nonhuman, researchers showed up at Seattle parks carrying a stuffed crow and recorded the reactions. One crow signals an alarm, then dozens show up. They surround the dead crow, looking at it as they perch on trees or fly above it, a behavior called mobbing. “Crows have evolved to have these complex social relationships, and they have a big brain,” said Kaeli Swift, a University of Washington graduate student who led the study.
How did evolution produce a monstrous killer like T. rex? A fossil find in Central Asia is giving scientists a glimpse of the process. T. rex and other tyrannosaurs were huge, dominant predators, but they evolved from much smaller ancestors. The new discovery from Uzbekistan indicates that this supersizing happened quickly, and only after the appearance of some anatomical features that may have helped the monster tyrannosaurs hunt so effectively. The finding was reported Monday by Hans-Dieter Sues of the Smithsonian's National Museum of Natural History in Washington, Stephen Brusatte of the University of Edinburgh in Scotland, and others in a paper released by the Proceedings of the National Academy of Sciences. The discovery They report finding bones of a previously unknown member of the evolutionary branch that led to the huge tyrannosaurs. This earlier dinosaur lived about 90 million years ago, south of what is now the Aral Sea. It looked roughly like a T. rex, but was only about 10 to 12 feet long and weighed only about 600 pounds at most, Sues said. T. rex grew about four times as long and weighed more than 20 times as much. The discovery helps fill in a frustrating gap in the tyrannosaur fossil record. Before that gap, which began some 100 million years ago, the ancestral creatures were only about as big as a horse. Right after the gap, at about 80 million years ago, tyrannosaurs were multi-ton behemoths like T. rex. The new finding shows the forerunners were still relatively small even just 90 million years ago. So the size boom happened pretty quickly. Standard equipment ©2016 CBC/Radio-Canada.
Link ID: 21989 - Posted: 03.15.2016
Carl Zimmer Scientists recently turned Harvard’s Skeletal Biology Laboratory into a pop-up restaurant. It would have fared very badly on Yelp. Katherine D. Zink, then a graduate student, acted as chef and waitress. First, she attached electrodes to the jaws of diners to record the activity in the muscles they use to chew food. Then she brought out the victuals. Some volunteers received a three-course vegetarian meal of carrots, yams or beets. In one course, the vegetables were cooked; in the second, they were raw and sliced; in the last course, Dr. Zink simply served raw chunks of plant matter. Other patrons got three courses of meat (goat, in this case). Dr. Zink grilled the meat in the first course, but offered it raw and sliced in the second. In the third course, her volunteers received an uncooked lump of goat flesh. In some of the trials, the volunteers chewed the food until it was ready to swallow and then spat it out. Dr. Zink painstakingly picked apart those food bits and measured their size. Every week, we'll bring you stories that capture the wonders of the human body, nature and the cosmos. “If that was all my dissertation was, I would have quit graduate school,” Dr. Zink said. “It was as lovely as it sounds.” Dr. Zink persevered, however, because she was exploring a profound question about our origins: How did our ancestors evolve from small-brained, big-jawed apes into large-brained, small-jawed humans? Scientists studying the fossil record have long puzzled over this transition, which happened around two million years ago. Before then, early human relatives — known as hominins — were typically about the size of chimpanzees, with massive teeth and a brain only a third the size of humans’ current brains. © 2016 The New York Times Company
By Jerome Siegel To say whether an animal sleeps requires that we define sleep. A generally accepted definition is that sleep is a state of greatly reduced responsiveness and movement that is homeostatically regulated, meaning that when it is prevented for a period of time, the lost time is made up—an effect known as sleep rebound. Unfortunately, the application of this definition is sometimes difficult. Can an animal sleep while it is moving and responsive? How unresponsive does an animal have to be? How much of the lost sleep has to be made up for it to be considered homeostatically regulated? Is the brain activity that characterizes sleep in humans necessary and sufficient to define sleep in other animals? Apart from mammals, birds are the only other animals known to engage in both slow-wave and rapid eye movement (REM) sleep. Slow-wave sleep, also called non-REM sleep, is characterized by slow, high-amplitude waves of electrical activity in the cortex and by slow, regular respiration and heart rate. During REM sleep, animals exhibit a waking-like pattern of cortical activity, as well as physiological changes including jerky eye twitches and increased variability of heart rate and respiration. (See “The A, B, Zzzzs.”) But many more animals, including some insects and fish, engage in behaviors that might be called sleep, such as resting with slow but regular respiration and heart rates and a desensitization to environmental stimuli. In addition to diversity in the neural and physiological correlates of sleep, species vary tremendously in the intensity, frequency, and duration of sleep. Some animals tend to nap intermittently throughout the day, while others, including humans, tend to consolidate their sleep into a single, long slumber. The big brown bat is the current sleep champion, registering 20 hours per day; giraffes and elephants doze less than four hours daily. © 1986-2016 The Scientist
It’s the most ancient nervous system we’ve ever seen, preserved inside 520 million-year-old fossils. What’s more, the nervous systems of these creatures’ modern-day descendants are less intricate, proving that evolution isn’t a one-way street to complexity. Found in South China, the five Cambrian fossils belonged to a group of organisms that gave rise to the arthropods, including insects, spiders and crustaceans. The fossils are of Chengjiangocaris kunmingensis, a creature around 10 centimetres long, with a segmented body, multiple pairs of legs and a heart-shaped head. But most interesting of all is its nerve cord and associated neurons. Together, the fossils show the entire nervous system of the organism, apart from its brain – making this the oldest preserved nervous system that has ever been found. “The detail of this fossil is exquisite,” says Rob DeSalle of the American Museum of Natural History in New York, who was not involved in the work. “The information from this specimen unravels transitions in how the nervous systems of arthropods evolved.” The animal had a nerve cord that ran the length of its body, with bulbous nodes of neurons called ganglia located between each pair of legs. “It’s almost like a mini-brain for each pair of legs,” says Javier Ortega-Hernández of the University of Cambridge, whose team analysed and described the fossil. Surprisingly, the team found dozens of fine, subsidiary nerves fanning out across the entire length of the nerve cord, making this nervous system more complex than those seen in today’s descendants. © Copyright Reed Business Information Ltd.
Link ID: 21941 - Posted: 03.01.2016
The dodo is an extinct flightless bird whose name has become synonymous with stupidity. But it turns out that the dodo was no bird brain, but instead a reasonably brainy bird. Scientists said on Wednesday they figured out the dodo's brain size and structure based on an analysis of a well-preserved skull from a museum collection. They determined its brain was not unusually small but rather completely in proportion to its body size. They also found the dodo may have had a better sense of smell than most birds, with an enlarged olfactory region of the brain. This trait, unusual for birds, probably let it sniff out ripe fruit to eat. The research suggests the dodo, rather than being stupid, boasted at least the same intelligence as its fellow members of the pigeon and dove family. Mauritius Dodo bird A skeleton of a Mauritius Dodo bird stands at an exhibition in the Mauritius Institute Museum in Port Louis in this Dec. 27, 2005 file photo. (Reuters) "If we take brain size — or rather, volume, as we measured here — as a proxy for intelligence, then the dodo was as smart as a common pigeon," paleontologist Eugenia Gold of Stony Brook University in New York state said. "Common pigeons are actually smarter than they get credit for, as they were trained as message carriers during the world wars." ©2016 CBC/Radio-Canada.
By Ann Gibbons Depressed? Your inner Neandertal may be to blame. Modern humans met and mated with these archaic people in Europe or Asia about 50,000 years ago, and researchers have long suspected that genes picked up in these trysts might be shaping health and well-being today. Now, a study in the current issue of Science details their impact. It uses a powerful new method for scanning the electronic health records of 28,000 Americans to show that some Neandertal gene variants today can raise the risk of depression, skin lesions, blood clots, and other disorders. Neandertal genes aren’t all bad. “These variants sometimes protect against a disease, sometimes make people more susceptible to disease,” says paleogeneticist Svante Pääbo of the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany. Two other new studies identified three archaic genes that boost immune response. And most archaic genes that persist in humans were likely beneficial in prehistoric times. But some now cause disease because modern lifestyles and environments are so different. Living people carry only trace amounts of Neandertal DNA, which makes its impact on health more striking. “The Neandertal genetic contribution to present-day people seems to have larger physiological effects than I would have naïvely thought,” says Pääbo, who helped launch this avenue of research by sequencing the first ancient genomes but was not involved in these studies. On average, Europeans and Asians have inherited about 1.5% of their genomes from Neandertals. Island Melanesians carry an additional 2% to 3% of DNA inherited from another extinct group, the Denisovans. Most Africans lack this archaic DNA because the interbreeding happened after modern humans left Africa. © 2016 American Association for the Advancement of Science
By Virginia Morell Like fearful humans, horses raise the inner brow of their eyes when threatened or surprised. Altogether their faces can convey 17 emotions (ours express 27), and they readily recognize the expressions on their fellow equines. But can they read our facial cues? To find out, researchers tested 28 horses, including 21 geldings and seven mares, from stables in the United Kingdom. Each horse was led by his/her halter rope to a position in the stable, and then presented with a life-size color photograph of the face of a man. The man was either smiling or frowning angrily. The scientists recorded the animals’ reactions, and measured their heart rates. Other studies have shown that stressed horses’ heart rates fluctuate, and when the horses looked at the angry man, their hearts reached a maximum heart rate more quickly than when they viewed the smiling image. When shown the angry face, 20 of the horses also turned their heads so that they could look at it with their left eye—a response that suggests they understood the expression, the scientists report online today in Biology Letters, because the right hemisphere of the brain is specialized for processing negative emotions. Dogs, too, have this “left-gaze bias” when confronting angry faces. Also, like dogs, the horses showed no such bias, such as moving their heads to look with the right eye, when viewing the happy faces—perhaps because the animals don’t need to respond to nonthreatening cues. But an angry expression carries a warning—the person may be about to strike. The discovery that horses as well as dogs—the only two animals this has been tested in—can read our facial expressions spontaneously and without training suggests one of two things: Either these domesticated species devote a lot of time to learning our facial cues, or the ability is innate and more widespread in the animal kingdom than previously thought. © 2016 American Association for the Advancement of Scienc
Fears over surveillance seem to figure large in the bird world, too. Ravens hide their food more quickly if they think they are being watched, even when no other bird is in sight. It’s the strongest evidence yet that ravens have a “theory of mind” – that they can attribute mental states such as knowledge to others. Many studies have shown that certain primates and birds behave differently in the presence of peers who might want to steal their food. While some researchers think this shows a theory of mind, others say they might just be reacting to visual cues, rather than having a mental representation of what others can see and know. Through the peephole Thomas Bugnyar and colleagues at the University of Vienna, Austria, devised an experiment to rule out the possibility that birds are responding to another’s cues. The setup involved two rooms separated by a wooden wall, with windows and peepholes that could be covered. First, a raven was given food with another raven in the next room, with the window open or covered, to see how quickly it caches its prize. With the window open, the birds hid their food more quickly and avoided going back to conceal it further. Then individual ravens were then trained to use the peephole to see where humans were putting food in the other room. The idea here was to allow the bird to realise it could be seen through the peephole. © Copyright Reed Business Information Ltd.