Chapter 1. An Introduction to Brain and Behavior

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By Ashutosh Jogalekar As marijuana is being legalized in Washington and Colorado states, its proliferation and use raise legitimate issues regarding its dose-dependent and long-term effects. One key question is whether pot leads to cognitive decline and a lowering of IQ, especially if its consumption is started at an early age. Answering this question is important for users, families and policy makers to have a realistic idea of personal and legal policies regarding widespread cannabis use. Last year, Madeline Meier and her group from Duke University reported results from the so-called Dunedin study which tracked a group of 1037 people from their birth to age 38. These volunteers’ pot smoking histories were monitored at periodic intervals from age 18 onwards. The study found a troubling decline of IQ and cognitive abilities among regular pot smokers, especially those whose habit kicked in during their teens. No explicit causal relationship was assigned between the two facts, but the correlation was positive and significant. The study naturally raised a lot of questions regarding the wisdom of early pot use, especially in light of its current legalization in two states. Now a study by Ole Rogeberg from the Ragnar Frisch Center for Research in Norway has called this study into question, both for its methodology and its conclusions. The first thing to realize about any such study, even if you don’t know the details, is that there are going to be several confounding socioeconomic factors in assessing any relationship between cannabis use and IQ. Medicine and psychology are not exact sciences, and following a large sample of people for 38 years and assessing correlation – let alone causation – between any two factors is going to be confounded by a large number of other correlated and uncorrelated variables in an inherently uncontrolled experiment. © 2013 Scientific American,

Keyword: Drug Abuse; Aggression
Link ID: 17690 - Posted: 01.17.2013

By CLAUDIA DREIFUS In a world of proliferating professions, S. Matthew Liao has a singular title: neuroethicist. Dr. Liao, 40, the director of the bioethics program at New York University, deploys the tools of philosophy, history, psychology, religion and ethics to understand the impact of neuroscientific breakthroughs. You’re a philosopher by training. How did philosophy lead to neuroethics? Mine’s the typical immigrant’s story. My family moved to Cincinnati from Taiwan in the early 1980s. Once here, my siblings gravitated towards the sciences. I was the black sheep. I was in love with the humanities. So I didn’t go to M.I.T. — I went to Princeton, where I got a degree in philosophy. This, of course, worried my parents. They’d never met a philosopher with a job. Do you have any insight on why scientific careers are so attractive to new Americans? You don’t need to speak perfect English to do science. And there are job opportunities. Define neuroethics. It’s a kind of subspecialty of bioethics. Until very recently, the human mind was a black box. But here we are in the 21st century, and now we have all these new technologies with opportunities to look inside that black box — a little. With functional magnetic imaging, f.M.R.I., you can get pictures of what the brain is doing during cognition. You see which parts light up during brain activity. Scientists are trying to match those lights with specific behaviors. At the same time this is moving forward, there are all kinds of drugs being developed and tested to modify behavior and the mind. So the question is: Are these new technologies ethical? © 2012 The New York Times Company

Keyword: Miscellaneous
Link ID: 17614 - Posted: 12.18.2012

By Dwayne Godwin and Jorge Cham Dwayne Godwin is a neuroscientist at the Wake Forest University School of Medicine. Jorge Cham draws the comic strip Piled Higher and Deeper at www.phdcomics.com. © 2012 Scientific American

Keyword: Miscellaneous
Link ID: 17504 - Posted: 11.19.2012

Neuroscientists at the University of Ingberg have found a brain region that does absolutely nothing. Their research, presented at the annual Society for Neuroscience meeting, showed that a small region of the cortex located near the posterior section of the cingulate gyrus responded to ‘not one of our 46 experimental manipulations’. Dr. Ahlquist was rather surprised at the finding. “During a pilot study we noticed that this small section of the cortex did not show differential activity in any of our manipulations. Out of curiosity, we wanted to see whether it actually did anything at all. Over the months that followed we tried every we knew, with over 20 different participants. IQ tests, memory tasks, flashing lights, talking, listening, imagining juggling, but there was no response. Nothing. We got more desperate, so we tried pictures of faces, TMS, pictures of cats, pictures of sex, pictures of violence and even sexy violence, but nothing happened! Not even a decrease. No connectivity to anywhere else, not even a voodoo correlation. 46 voxels of wasted space. I know dead salmons that are more responsive. It’s an evolutionary disgrace, that’s what it is.” Some neuroscientists are disappointed by the regions’ lack of response: ‘This is exactly the type of cortical behavior that leads to this popular science nonsense about using only 10% of our brain. Frankly, I am outraged by this lazy piece of brain. It’s the cortical equivalent of a spare tyre. If anyone wants to have it lobotomized, I am happy to break out the orbitoclast and help them out. That’ll teach it.”

Keyword: Brain imaging
Link ID: 17464 - Posted: 11.07.2012

by Virginia Morell Alex, an African grey parrot who died 5 years ago and was known for his ability to use English words, also understood a great deal about numbers. In a new study in this month's Cognition, scientists show that Alex correctly inferred the relationship between cardinal and ordinal numbers, an ability that has not previously been found in any species other than humans. After learning the cardinal numbers—or exact values—of one to six, Alex was taught the ordinal values (the position of a number in a list) of seven and eight—that is, he learned that six is less than seven, and seven is less than eight. He was never taught the cardinal values of seven and eight—but when tested on this, he passed with flying colors, apparently inferring, for instance, that the sound "seven" meant six plus one. In the video above of one of these experiments, comparative psychologist Irene Pepperberg of Harvard University asks Alex to pick out the set of colored blocks that equal the number seven. Play the video to hear his answer. © 2010 American Association for the Advancement of Science.

Keyword: Intelligence; Aggression
Link ID: 17458 - Posted: 11.06.2012

By Cari Nierenberg The strange folds and furrows covering a Brazilian man's entire scalp was neither a funky new look nor a hipster trend. Rather the 21-year-old's bizarre looking scalp with its deep skin folds in a pattern said to resemble the surface of the brain is a sign of a rare medical condition known as cutis verticis gyrata. In this week's New England Journal of Medicine, two Brazilian doctors describe this young man's case and share a picture of its odd appearance. When he was 19, the skin on his scalp started to change. It grew thicker, forming many soft, spongy ridges and narrow ruts. Even his hair had an unusual configuration. It was normal in the furrows but sparser over the folds as is common for this strange scalp condition. No doubt, visits to the barber shop as well as washing his squishy scalp and combing his hair were peculiar experiences. Despite the extent of his scalp affected, "the patient did not have the habit of covering his head," with a hat, for instance, says Dr. Karen Schons a dermatologist at the Hospital Universitario de Santa Maria, who examined the patient and co-authored the case study. In fact, the case study reports that "the condition did not bother him cosmetically." © 2012 NBCNews.com

Keyword: Miscellaneous
Link ID: 17386 - Posted: 10.18.2012

by Elizabeth Norton Baboons, like people, really do get by with a little help from their friends. Humans with strong social ties live longer, healthier lives, whereas hostility and "loner" tendencies can set the stage for disease and early death. In animals, too, strong social networks contribute to longer lives and healthier offspring—and now it seems that personality may be just as big a factor in other primates' longevity status. A new study found that female baboons that had the most stable relationships with other females weren't always the highest up in the dominance hierarchy or the ones with close kin around—but they were the nicest. Scientists are increasingly seeing personality as a key factor in an animal's ability to survive, adapt, and thrive in its environment. But this topic isn't an easy one to study scientifically, says primatologist Dorothy Cheney of the University of Pennsylvania. "Research in mammals, birds, fish, and insects shows individual patterns of behavior that can't be easily explained. But the many studies of personality are based on human traits like conscientiousness, agreeableness, or neuroticism. It isn't clear how to apply those traits to animals," Cheney says. Along with a group of scientists—including co-authors Robert Seyfarth, also at the University of Pennsylvania, and primatologist Joan Silk of Arizona State University, Tempe—Cheney has studied wild baboons at the Moremi Game Reserve in Botswana for almost 20 years. Besides providing detailed, long-term observations of behavior in several generations of baboons, the research has yielded a wealth of biological and genetic information. © 2010 American Association for the Advancement of Science.

Keyword: Evolution; Aggression
Link ID: 17323 - Posted: 10.02.2012

Zoë Corbyn Conventional wisdom says that most retractions of papers in scientific journals are triggered by unintentional errors. Not so, according to one of the largest-ever studies of retractions. A survey1 published in Proceedings of the National Academy of Sciences has found that two-thirds of retracted life-sciences papers were stricken from the scientific record because of misconduct such as fraud or suspected fraud — and that journals sometimes soft-pedal the reason. The survey examined all 2,047 articles in the PubMed database that had been marked as retracted by 3 May this year. But rather than taking journals’ retraction notices at face value, as previous analyses have done, the study used secondary sources to pin down the reasons for retraction if the notices were incomplete or vague. These sources included investigations by the US Office of Research Integrity, and evidence reported by the blog Retraction Watch. The analysis revealed that fraud or suspected fraud was responsible for 43% of the retractions. Other types of misconduct — duplicate publication and plagiarism — accounted for 14% and 10% of retractions, respectively. Only 21% of the papers were retracted because of error (see ‘Bad copy’). Earlier studies had found that the percentage of retractions attributable to error was 1.5–3 times higher2–4. “The secondary sources give a very different picture,” says Arturo Casadevall, a microbiologist at Yeshiva University in New York, and a co-author of the latest study. “Retraction notices are often not accurate.” © 2012 Nature Publishing Group

Keyword: Miscellaneous
Link ID: 17322 - Posted: 10.02.2012

By AMANDA SCHAFFER For years, researchers have investigated how the body loses the ability to produce enough insulin, a hallmark of diabetes. Now an intriguing theory is emerging, and it suggests a potential treatment that few scientists had considered. The hormone insulin helps shuttle glucose, or blood sugar, from the bloodstream into individual cells to be used as energy. But the body can become resistant to insulin, and the beta cells of the pancreas, which produce the hormone, must work harder to compensate. Eventually, the thinking goes, they lose the ability to keep up. “We used to say that the beta cells poop out,” said Alan Saltiel, director of the Life Sciences Institute at the University of Michigan. In reality, he added, this shorthand meant “we have no idea what’s going on.” Some evidence suggested that large numbers of these cells died through a process of programmed cell death called apoptosis. But that was at best a partial explanation. Now, researchers at Columbia University have put forth a surprising alternative. In mice with Type 2 diabetes, the researchers showed that beta cells that had lost function were not dead at all. Most remained alive, but in a changed form. They reverted to an earlier developmental, “progenitor,” state. It’s as if these cells are “stepping back in time to a point where they look like they might have looked during their development,” said Dr. Domenico Accili, director of the Columbia University Diabetes and Endocrinology Research Center, who led the new work. © 2012 The New York Times Company

Keyword: Stress; Aggression
Link ID: 17321 - Posted: 10.02.2012

By Gregory Thomas, During an introductory psychology course at Britain’s University of Essex in 2009, Arnold Wilkins asked his class to participate in a quick experiment. Wilkins projected two images on a wall and asked students to write down whether they found either of them disturbing. One was a photograph of a woody landscape. The other was a close-up of a lotus-flower seedpod — a flat-faced pod pocked with small holes. Most of the students were unmoved, but one, freshman An Le, recalls being both transfixed and revolted by the lotus image. “It felt like I was in shock,” he says. Le is far from alone in his response. Thousands of people claim to suffer trypophobia, a term derived from the Greek “trypo,” which means punching, drilling or boring holes. It refers to an irrational fear of clusters of small holes, such as beehives, ant holes and even bubbles in a pancake on the griddle or air pockets in a chocolate bar. On Web sites and blogs, self-diagnosed trypophobes share tales of vomiting, sleep loss and anxiety attacks at the sight of such objects as honeycombs and rotting wood. They say the fears are haunting and disruptive of their daily lives. But the medical world hasn’t yet embraced the phobia as real. Trypophobia isn’t listed in any major dictionary or in the Diagnostic and Statistical Manual of Mental Disorders. Attempts to add trypophobia to the Oxford English Dictionary and even to establish a Wikipedia page have been rebuffed because there hasn’t been any research published on the subject. A Wikipedia editor who deleted an entry on trypophobia in 2009 noted that trypophobia is “likely hoax and borderline patent nonsense.” © 1996-2012 The Washington Post

Keyword: Emotions; Aggression
Link ID: 17320 - Posted: 10.02.2012

By BENEDICT CAREY Proposed changes to the official diagnosis of autism will not reduce the proportion of children found to have it as steeply as many have feared, scientists reported on Tuesday, in an analysis that contradicts several previous studies. Earlier research had estimated that 45 percent or more of children currently on the “autism spectrum” would not qualify under a new definition now being refined by psychiatric researchers — a finding that generated widespread anxiety among parents who rely on state-financed services for their children. The new report, posted online Tuesday by The American Journal of Psychiatry, concluded that the number who would be excluded is closer to 10 percent. The finding may soothe the anxieties of some parents, but will not likely settle the debate over the effect of the new diagnosis. All sides agree that the proposed criteria are narrower and will likely result in fewer diagnoses of autism, but until doctors begin using the new definition widely, the predictions of its effect are just that: predictions. The debate has simmered over the past year as an expert panel appointed by the American Psychiatric Association has updated its proposals for the association’s Diagnostic and Statistical Manual of Mental Disorders, scheduled to take effect in May 2013. The manual is the field’s standard reference, and several recent studies suggested that the amended autism definition was far narrower than intended. © 2012 The New York Times Company

Keyword: Autism
Link ID: 17319 - Posted: 10.02.2012

By Simon J Makin Humans are born to a longer period of total dependence than any other animal we know of, and we also know that mistreatment or neglect during this time often leads to social, emotional, cognitive and mental health problems in later life. It’s not hard to imagine how a lack of proper stimulation in our earliest years – everything from rich sensory experiences and language exposure to love and care – might adversely affect our development, but scientists have only recently started to pull back the curtain on the genetic, molecular and cellular mechanisms that might explain how these effects arise in the brain. You’ll often hear it said that human beings are “social animals”. What biologists tend to mean by that phrase is behaviour like long-lasting relationships or some kind society, whether that’s the social hierarchy of gorillas or the extreme organisation of bees and ants. But, to an extent, most animals are social. A mother usually bonds with its offspring in any species of bird or mammal you care to mention, and almost all animals indulge in some kind of social behaviour when they mate. But there is another sense in which most animals seem to be fundamentally social. There is an emerging scientific understanding of the way social experience moulds the biochemistry of the brain and it looks like most species don’t just prefer the company of others – they need it to develop properly. Take that staple of genetics research, drosophila – aka the fruit fly. While they are not as social as primates or bees, they are more social than you might think, and there have been studies showing that social isolation can disrupt their mating behaviour or even reduce their lifespan. © 2012 Scientific American,

Keyword: Development of the Brain; Aggression
Link ID: 17318 - Posted: 10.02.2012

By NICHOLAS BAKALAR A small study has found that obese children are more likely than others to have a weak sense of taste. German researchers tested tasting ability in 99 obese and 94 normal-weight children, whose average age was 13, by having them try to identify tastes on strips of filter paper and asking them to distinguish among sweet, sour, salty, umami (savory) and bitter. The children also were asked to rate the taste’s intensity on a five-point scale. Girls were better than boys at distinguishing tastes, and older children scored higher than younger; there were no differences by ethnicity. Obese children scored an average of 12.6 out of a possible 20, while the normal-weight children averaged 14.1, a statistically significant difference. On the intensity scale, obese children rated all flavor concentrations lower than did those in the normal-weight group. “We think it’s important, especially for young children, to get different tastes so that they can improve their taste sensitivity,” said the lead author, Dr. Johanna Overberg, a pediatrician at Charité Children’s Hospital in Berlin. “If you taste more and different things at younger ages, you can do this.” The authors, writing online in the Archives of Disease in Childhood, say the reason for the association is unclear, but they suggest that the hormone leptin may affect both body weight and the sensitivity of taste buds. Copyright 2012 The New York Times Company

Keyword: Obesity; Aggression
Link ID: 17317 - Posted: 10.02.2012

by Jessica Hamzelou California has become the first US state to ban unfounded therapies that attempt to turn gay teenagers straight. "These practices have no basis in science or medicine and they will now be relegated to the dustbin of quackery," said state governor Jerry Brown in a statement to the San Francisco Chronicle. He signed a bill outlawing the therapies on 29 September. Brown's conclusions are in line with those reached a few years ago by a task force of psychologists who were commissioned by the American Psychological Association to assess all published research on the therapies. The group, led by Judith Glassgold, found no evidence that the treatment was effective. "The scientific evidence does not support such therapies," says Clinton Anderson, director of the APA's Lesbian, Gay, Bisexual and Transgender Concerns office. "They were not helpful and could be harmful," says Glassgold, who is based in Washington DC. "Most people became more depressed and anxious, and could become suicidal." "Usually these talk therapies are based on the assumption that homosexuality is a mental illness caused by poor parenting and confused gender roles," she adds. "They attempt to explain that to the patient, and try to get them to act and behave in a heterosexual manner." © Copyright Reed Business Information Ltd

Keyword: Sexual Behavior
Link ID: 17316 - Posted: 10.02.2012

By Tori Rodriguez A common complaint about wrinkle-masking Botox is that recipients have difficulty displaying emotions on their faces. That side effect might be a good thing, however, for people with treatment-resistant depression. In the first randomized, controlled study on the effect of botulinum toxin—known commercially as Botox—on depression, researchers investigated whether it might aid patients with major depressive disorder who had not responded to antidepressant medications. Participants in the treatment group were given a single dose (consisting of five injections) of botulinum toxin in the area of the face between and just above the eyebrows, whereas the control group was given placebo injections. Depressive symptoms in the treatment group decreased 47 percent after six weeks, an improvement that remained through the 16-week study period. The placebo group had a 9 percent reduction in symptoms. The findings appeared in May in the Journal of Psychiatric Research. Study author M. Axel Wollmer, a psychiatrist at the University of Basel in Switzerland, believes the treatment “interrupts feedback from the facial musculature to the brain, which may be involved in the development and maintenance of negative emotions.” Past studies have shown that Botox impairs people's ability to identify others' feelings, and the new finding adds more evidence: the muscles of the face are instrumental for identifying and experiencing emotions, not just communicating them. © 2012 Scientific American

Keyword: Depression; Aggression
Link ID: 17315 - Posted: 10.02.2012

Clint Witchalls James R. Flynn is Professor Emeritus at the University of Otago, New Zealand. Flynn researches intelligence and is best known for the discovery that, over the past century, IQs have been rising at a rate of about 3 points per decade (the Flynn-effect). In advance of his new book on the subject, Clint Witchalls asked him about this and some of Professor Flynn's more recent research findings: Clint Witchalls: How has our way of thinking and of solving problems changed over the past century? James R. Flynn: Today we take it for granted that using logic on the abstract is an ability we want to cultivate and we are interested in the hypothetical. People from 1900 were not scientifically oriented but utilitarian and they used logic, but to use it on the hypothetical or on abstractions was foreign to them. Alexander Luria [a Soviet psychologist] went to talk to headmen in villages in rural Russia and he said to them: "Where there is always snow, bears are white. At the North Pole there is always snow, what colour are the bears there?" And they said: "I've only seen brown bears." And he said: "What do my words convey?" And they said: "Such a thing as not to be settled by words but by testimony." They didn't settle questions of fact by logic, they settled them by experience. Your research found that we have gained 30 points on IQ tests in a century. What is the reason? The ultimate cause of why IQs are rising is the industrial revolution. The proximate cause is how our minds differ from people in 1900 when in the test room. And the intermediate causes, of course, are more cognitively demanding work roles, more cognitively demanding leisure, more formal schooling, and smaller families. © independent.co.uk

Keyword: Intelligence; Aggression
Link ID: 17307 - Posted: 09.27.2012

By Melissa Healy Los Angeles Times Measuring human intelligence may be controversial and oh-so-very-tricky to do. But like obscenity, we think we know it when we see it. A new study, however, demonstrates a more rigorous way to see and measure differences in intelligence between individuals. It finds that connectedness among the brain's disparate regions is a key factor that separates the plodding from the penetrating. As many researchers have long suspected, intelligence does have a "seat" in the human brain: an area just behind each of the temples called the lateral prefrontal cortex. But researchers writing in the journal Neuroscience found that human behavior that is exceptionally flexible, responsive and capable of navigating complexity requires something beyond a strong and active prefrontal cortex: strong and agile runners must link that seat to brain regions involved in perception, memory, language and mobility. The researchers estimate that the strength of those connections, as measured when subjects rested between mental tasks, explains about 10% of differences in intelligence among individuals. That makes this measure an even better predictor of intelligence than brain size -- a measure that scientists believe may explain about 7% of the variation in intelligence among individuals. To detect this relationship, the Neuroscience study compared functional magnetic resonance imaging (fMRI) brain scans of 78 men and women between 18 and 40 years old with those subjects' performance on tests of cognitive performance that required "fluid intelligence" and "cognitive control." Subjects, for instance, were asked to count backwards by, say, nine, or to watch a series of visual images and then indicate whether a single image shown had been among them. Copyright 2012

Keyword: Intelligence; Aggression
Link ID: 17117 - Posted: 08.04.2012

By Maria Konnikova It’s 1879, and psychology is just about to be born. The place: the University of Leipzig. The birth parent: Wilhelm Wundt. The deed: establishing the first official university laboratory for the study of psychology, an event taken by many as the line that marks unofficial explorations from empirical, accepted science. The laboratory has four rooms and a handful of students. By the early 1880s, it will grow to an astounding six rooms—and a total of 19 students. In 1883, it will award its first doctoral degree, to the first of Wundt’s advisees, Max Friedrich, on the topic of the time-course of individual psychological processes. That same year will see the publication of the first issue of the Journal Philosophische Studien, the first journal of experimental psychology, established—fittingly—by none other than Wundt. From that point on, the future of the discipline will be assured: psychology will survive, and perhaps even flourish, with the dawn of the new century. It will not be just another experiment gone wrong. That, at least, is the most straightforward story. It’s difficult to pinpoint a date for the birth of Psychology as such. That 1879 laboratory is but one contender, and Wundt, but one possible father. But just think of how many paved the way for Wundt’s achievements. Is it fair to call him the start, or is he rather more of a point of coalescence (if that)? And how far back must we go, if we’re to be really fair? © 2012 Scientific American,

Keyword: Miscellaneous
Link ID: 17114 - Posted: 08.01.2012

by Michael Balter Many children (and adults) have heard Aesop's fable about the crow and the pitcher. A thirsty crow comes across a pitcher partly filled with water but can't reach the water with his beak. So he keeps dropping pebbles into the pitcher until the water level rises high enough. A new study finds that both young children and members of the crow family are good at solving this problem, but children appear to learn it in a very different ways from birds. Recent studies, particularly ones conducted by Nicola Clayton's experimental psychology group at the University of Cambridge in the United Kingdom have shown that members of the crow family are no birdbrains when it comes to cognitive abilities. They can make and use tools, plan for the future, and possibly even figure out what other birds are thinking, although that last claim is currently being debated. A few years ago, two members of Clayton's group showed that rooks can learn to drop stones into a water-filled tube to get at a worm floating on the surface. And last year, a team led by Clayton's graduate student Lucy Cheke reported similar experiments with Eurasian jays: Using three different experimental setups, Cheke and her colleagues found that the jays could solve the puzzle as long as the basic mechanism responsible for raising the water level was clear to the birds. To explore how learning in children might differ from rooks, jays, and other members of the highly intelligent crow family, Cheke teamed up with a fellow Clayton lab member, psychologist Elsa Loissel, to try the same three experiments on local schoolchildren aged 4 to 10 years. Eighty children were recruited for the experiments, which took place at their school with the permission of their parents. © 2010 American Association for the Advancement of Science

Keyword: Intelligence; Aggression
Link ID: 17092 - Posted: 07.26.2012

by Elizabeth Pennisi OTTAWA—With big brains comes big intelligence, or so the hypothesis goes. But there may be trade-offs as well. Humans and other creatures with large brains relative to their body size tend to have smaller guts and possibly fewer offspring. Scientists have debated for decades whether the two phenomena are related. Now a team of researchers says that they are—and that big brains do indeed make us smart. The finding comes thanks to an unusual experiment reported here yesterday at the Evolution Ottawa evolutionary biology meeting in which scientists shrank and grew the brains of guppies over several generations. "This is a real experimental result," says David Reznick, an evolutionary biologist at the University of California, Riverside, who was not involved in the study. "The earlier results were just correlations." Researchers first began to gather evidence that big brains were advantageous after 19th century U.S. biologist Hermon Bumpus examined the brains of sparrows, some of whom had succumbed in a blizzard and some of whom survived. The survivors had relatively larger brains. More recently, evolutionary biologist Alexei Maklakov from Uppsala University in Sweden found evidence that songbirds that colonize cities tend to have larger brains relative to their body size than species still confined to the countryside. The challenge of urban life might require bigger brains, he and his colleagues concluded last year in Biology Letters. Yet in humans and in certain electric fish, larger brain size seems to have trade-offs: smaller guts and fewer offspring. That's led some scientists to suggest there are constraints on how big brains can become because they are expensive to build and maintain. © 2010 American Association for the Advancement of Science.

Keyword: Evolution; Aggression
Link ID: 17026 - Posted: 07.11.2012