Chapter 6. Evolution of the Brain and Behavior
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Carrie Arnold There was one sound that biologist Rusty Gonser always heard at Cranberry Lake — and there was one sound that he would never hear again. Every summer for more than 25 years, Gonser and his wife, Elaina Tuttle, had made the trip to this field station in the Adirondack Mountains — a 45-minute boat ride from the nearest road. Now, as he moored his boat to the shaky wooden dock, he heard a familiar and short song that sounded like 'oh-sweet-Canada'. The whistle was from a white-throated sparrow calling hopefully for a mate. What he didn't hear was the voice or laughter of his wife. For the first time, Gonser was at Cranberry Lake alone. Just a few weeks earlier, Tuttle had died of breast cancer. Her entire career, and most of Gonser's, had been devoted to understanding every aspect of the biology of the white-throated sparrow (Zonotrichia albicollis). Less than six months before she died this year at the age of 52, the couple and their team published a paper1 that was the culmination of that work. It explained how a chance genetic mutation had put the species on an extraordinary evolutionary path. The mutation had flipped a large section of chromosome 2, leaving it unable to pair up with a partner and exchange genetic information. The more than 1,100 genes in the inversion were inherited together as part of a massive 'supergene' and eventually drove the evolution of two different 'morphs' — subtypes of the bird that are coloured differently, behave differently and mate only with the opposite morph. Tuttle and Gonser's leap was to show that this process is nearly identical to the early evolution of certain sex chromosomes, including the human X and Y. The researchers realized that they were effectively watching the bird evolve two sex chromosomes, on top of the two it already had. © 2016 Macmillan Publishers Limited,
By Ann Gibbons On a promontory high above the sweeping grasslands of the Georgian steppe, a medieval church marks the spot where humans have come and gone along Silk Road trade routes for thousands of years. But 1.77 million years ago, this place was a crossroads for a different set of migrants. Among them were saber-toothed cats, Etruscan wolves, hyenas the size of lions—and early members of the human family. Here, primitive hominins poked their tiny heads into animal dens to scavenge abandoned kills, fileting meat from the bones of mammoths and wolves with crude stone tools and eating it raw. They stalked deer as the animals drank from an ancient lake and gathered hackberries and nuts from chestnut and walnut trees lining nearby rivers. Sometimes the hominins themselves became the prey, as gnaw marks from big cats or hyenas on their fossilized limb bones now testify. "Someone rang the dinner bell in gully one," says geologist Reid Ferring of the University of North Texas in Denton, part of an international team analyzing the site. "Humans and carnivores were eating each other." This is the famous site of Dmanisi, Georgia, which offers an unparalleled glimpse into a harsh early chapter in human evolution, when primitive members of our genus Homo struggled to survive in a new land far north of their ancestors' African home, braving winters without clothes or fire and competing with fierce carnivores for meat. The 4-hectare site has yielded closely packed, beautifully preserved fossils that are the oldest hominins known outside of Africa, including five skulls, about 50 skeletal bones, and an as-yet-unpublished pelvis unearthed 2 years ago. "There's no other place like it," says archaeologist Nick Toth of Indiana University in Bloomington. "It's just this mother lode for one moment in time." © 2016 American Association for the Advancement of Science.
Link ID: 22899 - Posted: 11.23.2016
James Gorman The Goffin’s cockatoo is a smart bird, so smart it has been compared to a 3-year-old human. But even for this species, a bird named Figaro stands out for his creativity with tools. Hand-raised at the Veterinary University of Vienna, the male bird was trying to play with a pebble that fell outside his aviary onto a wooden beam about four years ago. First he used a piece of bamboo to try to rake the stone back in. Impressed, scientists in the university Goffin’s lab, which specializes in testing the thinking abilities of the birds, put a cashew nut where the pebble had been. Figaro extended his beak through the wire mesh to bite a splinter off the wooden beam. He used the splinter to fish the cashew in, a fairly difficult process because he had to work the splinter through the mesh and position it at the right angle. In later trials, Figaro made his tools much more quickly, and also picked a bamboo twig from the bottom of the aviary and trimmed it to make a similar tool. Cockatoos don’t do anything like this in nature, as far as anyone knows. They don’t use tools. They don’t even build nests, so they are not used to manipulating sticks. And they have curved bills, unlike the straight beaks of crows and jays that make manipulating tools a bit easier. Blue jays have been observed creating tools from newspaper to pull food pellets to them. Alice M.I. Auersperg, a researcher at the Veterinary University of Vienna who studies cognition in animals, and her colleagues reported those first accomplishments by Figaro in 2012. Since then, they have continued to test Figaro and other birds in the lab that were able to learn tool use or tool making, sometimes both, by watching Figaro. © 2016 The New York Times Company
By STEPH YIN Neanderthals and modern humans diverged from a common ancestor about half a million years ago. Living in colder climes in Eurasia, Neanderthals evolved barrel chests, large skulls and strong hands. In Africa, modern humans acquired shorter faces, a prominent chin and slender limbs. Then, roughly 50,000 years ago, the two species encountered one another and interbred, as modern humans spread out of Africa. The legacy of this interbreeding has been the subject of much scientific inquiry in the past few years. Today, up to 4 percent of the genes of non-Africans are Neanderthal in origin.. These may have influenced a diverse range of traits, including keratin production, disease risk and the propensity to sneeze after eating dark chocolate. Where did all the other Neanderthal DNA go? Why did a Neanderthal-human hybrid not prevail? Two recent studies converge on an explanation. They suggest the answer comes down to different population sizes between Neanderthals and modern humans, and this principle of population genetics: In small populations, natural selection is less effective. “Neanderthals have this small population over hundreds of thousands of years, presumably because they’re living in very rough conditions,” said Graham Coop, a genetics professor at the University of California, Davis, and an author of one of the studies, published Tuesday in PLOS Genetics. As a result, Neanderthals were more inbred than modern humans and accumulated more mutations that have a slightly adverse effect, such as increasing one’s risk of disease, but do not prevent one from reproducing (and thus, passing such mutations along). © 2016 The New York Times Company
By Felicity Muth Kirsty Graham is a PhD student at the University of St Andrews, Scotland, who works on gestural communication of chimpanzees and bonobos in Uganda and DRCongo. I recently asked her some questions about the work that she does and some exciting recent findings of hers about how these animals communicate. How did you become interested in communication, and specifically gestures? Languages are fascinating – the diversity, the culture, the learning – and during undergrad, I became interested in the origins of our language ability. I went to Quest University Canada (a small liberal arts university) and learned that I could combine my love of languages and animals and being outdoors! Other great apes don’t have language in the way that humans do, but studying different aspects of communication, such as gestures, may reveal how language evolved. Although my interest really started from an interest in languages, once you get so deep into studying other species you become excited about their behaviour for its own sake. In the long run, it would be nice to piece together how language evolved, but for now I’m starting with a very small piece of the puzzle – bonobo gestures. How do you study gestures in non-human primates? There are a few different approaches to studying gestures: in the wild or in captivity; through observation or with experiments; studying one gesture in detail or looking at the whole repertoire. I chose to observe wild bonobos and look at their whole repertoire. Since not much is known about bonobo gestural communication, this seemed like a good starting point. During my PhD, I spent 12 months at Wamba (Kyoto University’s research site) in the DRCongo. I filmed the bonobos, anticipating the beginning of social interactions so that I could record the gestures that they use. Then I spent a long time watching the videos, finding gestures, and coding information about the gestures. © 2016 Scientific American
By Solomon Israel, A May-December romance brings benefits for young female gray jays mated to older males, according to new Canadian research. The paper, published this month in the journal Animal Behaviour, used almost four decades of data on a marked population of gray jays in Ontario's Algonquin Park to study how the birds adjust their reproductive habits in response to changes in temperature and other conditions. Gray jays, also known as Canada jays or whisky jacks, don't migrate south in the winter, instead living year-round in boreal forests across Canada and the northern U.S. They manage this feat of survival by caching food all over their large, permanent habitats, then retrieving it during the winter months. The small, fluffy birds take advantage of those winter supplies to nest much earlier than most other birds, laying eggs between late February and March. Gray jays don't migrate during the winter, instead relying on hidden caches of food to feed themselves and their offspring. (Dan Strickland) The researchers found that female gray jays that laid their eggs earlier in the season had the most reproductive success, with a higher survival rate for offspring. ©2016 CBC/Radio-Canada
By Virginia Morell Human hunters may be making birds smarter by inadvertently shooting those with smaller brains. That’s the conclusion of a new study, which finds that hunting may be exerting a powerful evolutionary force on bird populations in Denmark, and likely wherever birds are hunted. But the work also raises a red flag for some researchers who question whether the evolution of brain size can ever be tied to a single factor. The new work “broadens an emerging view that smarts really do matter in the natural, and increasingly human-dominated, world,” says John Marzluff, a wildlife biologist and expert on crow cognition at the University of Washington in Seattle who was not involved with the work. Hunting and fishing are known to affect many animal populations. For instance, the pike-perch in the Finnish Archipelago Sea has become smaller over time thanks to fishing, which typically removes the largest individuals from a population. This pressure also causes fish to reach sexual maturity earlier. On land, natural predators like arctic foxes and polar bears can also drive their prey species to become smarter because predators are most likely to catch those with smaller brains. For instance, a recent study showed that common eiders (maritime ducks) that raise the most chicks also have the largest heads and are better at forming protective neighborhood alliances than ducks with smaller heads—and presumably, brains. © 2016 American Association for the Advancement of Science
By Brian Owens Cooperation makes it happen. Sailfish that work together in groups to hunt sardines can catch more fish than if they hunt alone, even without a real coordinated strategy. To catch their sardine dinner, a group of sailfish circle a school of sardines – known as a baitball – and break off a small section, driving it to the surface. They then take turns attacking these sardines, slashing at them with their long sword-like bills, which account for a quarter of their total length of up to 3.5 metres. Knocking their prey off-balance makes them easier to grab. These attacks only result in a catch about 25 per cent of the time, but they almost always injure several sardines. As the number of injured fish increases, it becomes ever easier for everyone to snag a meal. “There’s no coordination, no strict turn-taking or specific hunting roles, it’s opportunistic,” says James Herbert-Read, from Uppsala University in Sweden. But Herbert-Reads computer models now show that even this rudimentary form of cooperation is better than going it alone. Sailfish that work in groups capture more sardines than a lone fish would get in the same amount of time. © Copyright Reed Business Information Ltd
Erin Wayman SALT LAKE CITY — The earliest primate was a tiny, solitary tree dweller that liked the night life. Those are just some conclusions from new reconstructions of the primate common ancestor, presented October 27 at the annual meeting of the Society of Vertebrate Paleontology. Eva Hoffman, now a graduate student at the University of Texas at Austin, and colleagues at Yale University looked at behavioral and ecological data from 178 modern primate species. Examining patterns of traits across the primate family tree, the researchers inferred the most likely characteristics of ancestors at different branching points in the tree — all the way back to the common ancestor. This ancient primate, which may have lived some 80 million to 70 million years ago, was probably no bigger than a guinea pig, lived alone and gave birth to one offspring at a time, the researchers suggest. Living in trees and active at night, the critter probably ventured out to the ends of tree branches to eat fruits, leaves and insects. But this mix of traits probably didn’t arise in primates, Hoffman says. After adding tree shrews and colugos — primates’ closest living relatives — to the analysis, the researchers concluded these same attributes were also present in the three groups’ common ancestor. So explanations of early primate evolution that rely on these features need to be reconsidered, Hoffman says. |© Society for Science & the Public 2000 - 2016.
Link ID: 22808 - Posted: 10.31.2016
Nicola Davis A brown, pebble-sized object found in a rock pool on a beach near Bexhill, Sussex bears the first evidence of fossilised dinosaur brain tissue, scientists say. Found in 2004 by an amateur fossil collector, the object is the cast of a dinosaur’s brain cavity, and appears to show a thin veneer of mineralised tissues on its surface. Scientists say the find is most likely from a relative of the Iguanodon, which lived around 125 million years ago. Large, hefty herbivores, Iguanodons reached up around eight metres in length, could walk on either two legs or all fours and boasted sharp spikes on their thumbs - a feature initially thought to be a horn on the nose and immortalised as such in the Victorian dinosaur sculptures of Crystal Palace Park. While casts of the inside of dinosaur brain cases have been found before, it is the first time fossilised brain soft tissue has been discovered for any land-living vertebrate. “The most striking thing is that something as delicate as brain tissue, and which you wouldn’t expect to ever see, has been preserved,” said Alex Liu, co-author of the research from the University of Cambridge. “It just speaks volumes [about] the spectacular preservational quality that can be obtained in the fossil record even 130 million years after this dinosaur is alive.” Writing in a special publication from the Geological Society of London to commemorate the work of the late co-author Martin Brasier, an international team of researchers describe how the cast was discovered near other dinosaur remains, including ribs and leg bones. “We can’t say it is from the same organism, but it is from a fairly large dinosaur,” said Liu. © 2016 Guardian News and Media Limited
Link ID: 22799 - Posted: 10.28.2016
By Brian Owens Chimpanzees and their relatives bonobos are closer than we thought. Bonobos seem to have donated genes to chimps at least twice in the roughly two million years since they last shared an ancestor. The two closely related apes have occasionally interbred in captivity, and bonobos are renowned for their free and easy sex life. But the finding that they interbred in the wild was unexpected. The two species split sometime between 1.5 and 2.1 million years ago, around the same time that the Congo River system formed. Wild bonobo populations are entirely contained in that river system, separated from two nearby subspecies of chimps, the eastern and central subspecies. Scientists assumed the river was an impenetrable barrier, says Christina Hvilsom from Copenhagen Zoo in Denmark, one of the researchers who worked on the genetic project. But it turns out that it must have been breached more than once – although it’s not clear how that happened. Hvilsom and her colleagues weren’t actually looking for genetic evidence of ancient interspecies erotica. They were mapping genetic markers that could be used to determine where illegally traded chimps came from so they could be returned to their homes in the wild. © Copyright Reed Business Information Ltd.
Link ID: 22798 - Posted: 10.28.2016
By Agata Blaszczak-Boxe Some rodents have a sweet tooth. And sometimes, you need to get crafty to reach your sugar fix. Rats have been filmed for the first time using hooked tools to get chocolate cereal – a manifestation of their critter intelligence. Akane Nagano and Kenjiro Aoyama, of Doshisha University in Kyotanabe, Japan, placed eight brown rats in a transparent box and trained them to pull small hooked tools to obtain the cereal that was otherwise beyond their reach. In one experiment they gave them two similar hooked tools, one of which worked well for the food retrieval task, and the other did not. The rats quickly learned to choose the correct tool for the job, selecting it 95 per cent of the time. The experiments showed that the rats understood the spatial arrangement between the food and the tool. The team’s study is the first to demonstrate that rats are able to use tools, says Nagano. The rats did get a little confused in the final experiment. When the team gave them a rake that looked the part but with a bottom was too soft and flimsy to move the cereal, they still tried to use it as much as the working tool that was also available. But, says Nagano, it is possible their eyesight was simply not good enough for them to tell that the flimsy tool wasn’t up to the task. The rodents’ crafty feat places them in the ever-growing club of known tool-using animals such as chimps, bearded capuchin monkeys, New Caledonian crows, alligators and even some fish. © Copyright Reed Business Information Ltd.
Hannah Devlin Science correspondent Monkeys have been observed producing sharp stone flakes that closely resemble the earliest known tools made by our ancient relatives, proving that this ability is not uniquely human. Previously, modifying stones to create razor-edged fragments was thought to be an activity confined to hominins, the family including early humans and their more primitive cousins. The latest observations re-write this view, showing that monkeys unintentionally produce almost identical artefacts simply by smashing stones together. The findings put archaeologists on alert that they can no longer assume that stone flakes they discover are linked to the deliberate crafting of tools by early humans as their brains became more sophisticated. Tomos Proffitt, an archaeologist at the University of Oxford and the study’s lead author, said: “At a very fundamental level - if you’re looking at a very simple flake - if you had a capuchin flake and a human flake they would be the same. It raises really important questions about what level of cognitive complexity is required to produce a sophisticated cutting tool.” Unlike early humans, the flakes produced by the capuchins were the unintentional byproduct of hammering stones - an activity that the monkeys pursued decisively, but the purpose of which was not clear. Originally scientists thought the behaviour was a flamboyant display of aggression in response to an intruder, but after more extensive observations the monkeys appeared to be seeking out the quartz dust produced by smashing the rocks, possibly because it has a nutritional benefit. © 2016 Guardian News and Media Limited
Link ID: 22771 - Posted: 10.20.2016
By Elizabeth Pennisi Although it has a face—and body—that only a mother could love, the naked mole rat has a lot to offer biomedical science. It lives 10 times longer than a mouse, almost never gets cancer, and doesn’t feel pain from injury and inflammation. Now, researchers say they’ve figured out how the rodents keep this pain away. “It’s an amazing result,” says Harold Zakon, an evolutionary neurobiologist at the University of Texas, Austin, who was not involved with the work. “This study points us to important areas … that might be targeted to reduce this type of pain.” Naked mole rats are just plain weird. They live almost totally underground in colonies structured like honey bee hives, with hundreds of workers servicing a single queen and her few consorts. To survive, they dig kilometers of tunnels in search of large underground tubers for food. It’s such a tough life that—to conserve energy—this member of the rodent family gave up regulating its temperature, and they are able to thrive in a low-oxygen, high–carbon dioxide environment that would suffocate or be very painful to humans. “They might as well be from another planet,” says Thomas Park, a neuroscientist at the University of Illinois, Chicago. Gary Lewin, a neuroscientist at the Max Delbrück Center for Molecular Medicine in the Helmholtz Association in Berlin, began working with naked mole rats because a friend in Chicago was finding that the rodent's pain fibers were not the same as other mammals'. In 2008, the studies led to the finding that naked mole rats didn’t feel pain when they came into contact with acid and didn’t get more sensitive to heat or touch when injured, like we and other mammals do. Lewin was hooked and has been raising the rodents in his lab ever since. They are a little more challenging than rats or mice, he notes, because with just one female per colony producing young, he never really has quite enough individuals for his studies. © 2016 American Association for the Advancement of Science
Bruce Bower Apes understand what others believe to be true. What’s more, they realize that those beliefs can be wrong, researchers say. To make this discovery, researchers devised experiments involving a concealed, gorilla-suited person or a squirreled-away rock that had been moved from their original hiding places — something the apes knew, but a person looking for King Kong or the stone didn’t. “Apes anticipated that an individual would search for an object where he last saw it, even though the apes knew that the object was no longer there,” says evolutionary anthropologist Christopher Krupenye. If this first-of-its-kind finding holds up, it means that chimpanzees, bonobos and orangutans can understand that others’ actions sometimes reflect mistaken assumptions about reality. Apes’ grasp of others’ false beliefs roughly equals that of human 2-year-olds tested in much the same way, say Krupenye of the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany, and his colleagues. Considering their targeted gazes during brief experiments, apes must rapidly assess others’ beliefs about the world in wild and captive communities, the researchers propose in the October 7 Science. Understanding the concept of false beliefs helps wild and captive chimps deceive their comrades, such as hiding food from those who don’t share, Krupenye suggests. |© Society for Science & the Public 2000 - 2016.
By Emily Underwood When you let forth a big, embarrassing yawn during a boring lecture or concert, you succumb to a reflex so universal among animals that Charles Darwin mentioned it in his field notes. “Seeing a dog & horse & man yawn, makes me feel how much all animals are built on one structure,” he wrote in 1838. Scientists, however, still don’t agree on why we yawn or where it came from. So in a new study, researchers watched YouTube videos of 29 different yawning mammals, including mice, kittens, foxes, hedgehogs, walruses, elephants, and humans. (Here is a particularly cute montage used in the study.) They discovered a pattern: Small-brained animals with fewer neurons in the wrinkly outer layer of the brain, called the cortex, had shorter yawns than large-brained animals with more cortical neurons, the scientists report today in Biology Letters. Primates tended to yawn longer than nonprimates, and humans, with about 12,000 million cortical neurons, had the longest average yawn, lasting a little more than 6 seconds. African elephants, whose brains are close to the same weight as humans’ and have a similar number of cortical neurons, lasted about 6 seconds. The yawns of tiny-brained mice, in contrast, were less than 1.5 seconds in duration. The study lends support to a long-held hypothesis that yawning has an important physiological effect, such as increasing blood flood to the brain and cooling it down, the scientists say. © 2016 American Association for the Advancement of Science.
Emily Underwood To human observers, bumblebees sipping nectar from flowers appear cheerful. It turns out that the insects may actually enjoy their work. A new study suggests that bees experience a “happy” buzz after receiving a sugary snack, although it’s probably not the same joy that humans experience chomping on a candy bar. Scientists can’t ask bees or other animals how they feel. Instead, researchers must look for signs of positive or negative emotions in an animal’s decision making or behavior, says Clint Perry, a neuroethologist at Queen Mary University of London. In one such study, for example, scientists shook bees vigorously in a machine for 60 seconds — hard enough to annoy, but not hard enough to cause injury — and found that stressed bees made more pessimistic decisions while foraging for food. The new study, published in the Sept. 30 Science, is the first to look for signs of positive bias in bee decision making, Perry says. His team trained 35 bees to navigate a small arena connected to a plastic tunnel. When the tunnel was marked with a blue flower, the bees learned that a tasty vial of sugar water awaited them at its end. When a green flower was present, there was no reward. Once the bees learned the difference, the scientists threw the bees a curveball: Rather than being blue or green, the flower had a confusing blue-green hue. Faced with the ambiguous blossom, the bees appeared to dither, meandering around for roughly 100 seconds before deciding whether to enter the tunnel. Some didn’t enter at all. But when the scientists gave half the bees a treat — a drop of concentrated sugar water — that group spent just 50 seconds circling the entrance before deciding to check it out. Overall, the two groups flew roughly the same distances at the same speeds, suggesting that the group that had gotten a treat first had not simply experienced a boost in energy from the sugar, but were in a more positive, optimistic state, Perry says. |© Society for Science & the Public 2000 - 2016.
Carl Zimmer Modern humans evolved in Africa roughly 200,000 years ago. But how did our species go on to populate the rest of the globe? The question, one of the biggest in studies of human evolution, has intrigued scientists for decades. In a series of extraordinary genetic analyses published on Wednesday, researchers believe they have found an answer. In the journal Nature, three separate teams of geneticists survey DNA collected from cultures around the globe, many for the first time, and conclude that all non-Africans today trace their ancestry to a single population emerging from Africa between 50,000 and 80,000 years ago. “I think all three studies are basically saying the same thing,” said Joshua M. Akey of the University of Washington, who wrote a commentary accompanying the new work. “We know there were multiple dispersals out of Africa, but we can trace our ancestry back to a single one.” The three teams sequenced the genomes of 787 people, obtaining highly detailed scans of each. The genomes were drawn from people in hundreds of indigenous populations: Basques, African pygmies, Mayans, Bedouins, Sherpas and Cree Indians, to name just a few. The DNA of indigenous populations is essential to understanding human history, many geneticists believe. Yet until now scientists have sequenced entire genomes from very few people outside population centers like Europe and China. © 2016 The New York Times Company
Link ID: 22682 - Posted: 09.22.2016
By Brian Owens It’s certainly something to crow about. New Caledonian crows are known for their ingenious use of tools to get at hard-to-reach food. Now it turns out that their Hawaiian cousins are adept tool-users as well. Christian Rutz at the University of St Andrews in the UK has spent 10 years studying the New Caledonian crow and wondered whether any other crow species are disposed to use tools. So he looked for crows that have similar features to the New Caledonian crow – a straight bill and large, mobile eyes that allow it to manipulate tools, much as archaeologists use opposable thumbs as an evolutionary signature for tool use in early humans. “The Hawaiian crow really stood out,” he says. “They look quite similar.” Hawaiian crows are extinct in the wild, but 109 birds still live in two captive breeding facilities in Hawaii. That meant Rutz was able to test pretty much every member of the species. He stuffed tasty morsels into a variety of holes and crevices in a log, and gave the birds a variety of sticks to see if they would use them to dig out the food. Almost all of them did, and most extracted the food in less than a minute, faster than the researchers themselves could. “It’s mind-blowing,” says Rutz. “They’re very good at getting the tool in the right position, and if they’re not happy with it they’ll modify it or make their own.” © Copyright Reed Business Information Ltd.
By JAMES GORMAN Who’s a good dog? Well, that depends on whom you’re asking, of course. But new research suggests that the next time you look at your pup, whether Maltese or mastiff, you might want to choose your words carefully. “Both what we say and how we say it matters to dogs,” said Attila Andics, a research fellow at Eotvos Lorand University in Budapest. Dr. Andics, who studies language and behavior in dogs and humans, along with Adam Miklosi and several other colleagues, reported in a paper to be published in this week’s issue of the journal Science that different parts of dogs’ brains respond to the meaning of a word, and to how the word is said, much as human brains do. Photo A dog waiting for its brain activity to be measured in a magnetic resonance imaging machine for research reported in the journal Science. Credit Enik Kubinyi As with people’s brains, parts of dogs’ left hemisphere react to meaning and parts of the right hemisphere to intonation — the emotional content of a sound. And, perhaps most interesting to dog owners, only a word of praise said in a positive tone really made the reward system of a dog’s brain light up. The experiment itself was something of an achievement. Dr. Andics and his colleagues trained dogs to enter a magnetic resonance imaging machine and lie in a harness while the machine recorded their brain activity. A trainer spoke words in Hungarian — common words of praise used by dog owners like “good boy,” “super” and “well done.” The trainer also tried neutral words like “however” and “nevertheless.” Both the praise words and neutral words were offered in positive and neutral tones. The positive words spoken in a positive tone prompted strong activity in the brain’s reward centers. All the other conditions resulted in significantly less action, and all at the same level. © 2016 The New York Times Company