Thursday, December 23, 2010

EXPOSURE TO MORE DIVERSE OBJECTS SPEEDS WORD LEARNING IN TOTS

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Two toddlers are learning the word “cup.” One sees three nearly identical cups; the other sees a tea cup, a sippy cup and a Styrofoam cup. Chances are, the second child will have a better sense of what a cup is and—according to a new University of Iowa study—may even have an advantage as he learns new words.

Published this month in the journal Psychological Science, a journal of the Association for Psychological Science, the research showed that 18-month-olds who played with a broader array of objects named by shape—for example, groups of bowls or buckets that were less similar in material, size or features—learned new words twice as fast as those who played with more similar objects.

Outside the lab, one month after the training, tots who had been exposed to the diverse objects were learning an average of nearly 10 new words per week. Kids in the other group were picking up four a week—the typical rate for children that age without any special training. Researchers aren’t sure how long the accelerated learning continued for the variable group, but they can explain why it may have occurred.

All of the children given extra training with words figured out that shape was the most important distinguishing feature when learning to name solid objects. This attention to shape, called a “shape bias,” is not typically seen until later in development. However, the researchers believe that kids exposed to more variety took the knowledge a step further, also learning when not to attend to shape. Tots in the variable group learned, for example, to focus on material rather than shape when hearing names for non-solid substances.

“Knowing where to direct their attention helps them learn words more quickly overall,” said lead author Lynn Perry, a UI doctoral student in psychology. “The shape bias enhances vocabulary development because most of the words young kids learn early on are names of categories organized by similarity in shape. And, developing the ability to disregard shape for non-solids helps them learn words like pudding, Jell-O, or milk.”

Perry conducted the study with psychologist Larissa Samuelson of the UI College of Liberal Arts and Sciences, and UI alumni Lisa Malloy and Ryan Schiffer. The study involved 16 children who knew about 17 object names when the study began. Half of the kids were taught names of objects by playing with groups of toys that were nearly identical; the other half used toys that differed significantly—for example, a small, cloth, jack-o-lantern bucket; a trash bucket with no handle; and a traditional plastic bucket.

When tested on unfamiliar objects that fit into the categories they’d been taught—such as a bucket they’d never seen before—kids in the variable group performed better. This showed an ability to generalize the knowledge.

“We believe the variable training gave them a better idea of what a bucket was. They discovered that the buckets were all alike in general shape, but that having a handle or being a particular texture didn’t matter,” Perry said. “In contrast, the children exposed to a tightly organized group of objects developed such strict criteria for what constitutes a bucket that they were reluctant to call it a bucket if it was different from what they’d learned.”

In additional tests, researchers looked at whether the tots learned names of new objects by focusing on substance or shape. The variable group tuned into shape for solids, but material for non-solids, a distinction that doesn’t typically develop until around age 3, when a child’s vocabulary reaches 150 nouns. Toddlers in the other group continued to fixate on shape, even if the object was made of, say, hair gel or shaving cream.

Further investigation is necessary to pinpoint exactly why the variable group had more success in this area, but the researchers say their study is the first to show that variability at the local level can help children learn something more global about the importance of particular object features for different categories of things.

“What children learn about one category sets the stage for their future learning,” Samuelson said. “Similar exemplars help children learn specific names for specific objects. But variable exemplars teach them more about the whole category, which helps them learn names of other new things faster. That’s why kids in the variable group learned more outside the lab—they learned more about naming in general, not just specific examples of the specific categories they’d seen in the lab.”

The study was funded by a National Institute of Child Health and Human Development grant awarded to Samuelson. Samuelson and Perry are members of the UI Delta Center, which focuses on research in the fields of learning and development.

Association for Psychological Science

IMITATING SOMEONES ACCENT MAKES IT EASIER TO UNDERSTAND THEM

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In conversation, we often imitate each other’s speech style and may even change our accent to fit that of the person we’re talking to. A recent study in Psychological Science, a journal of the Association for Psychological Science, suggests that imitating someone who speaks with a regional or foreign accent may actually help you understand them better.

“If people are talking to each other, they tend to sort of move their speech toward each other,” says Patti Adank, of the University of Manchester, who cowrote the study with Peter Hagoort and Harold Bekkering from Radboud University Nijmegen in the Netherlands. People don’t only do this with speech, she says. “People have a tendency to imitate each other in body posture, for instance in the way they cross their arms.” She and her colleagues devised an experiment to test the effect of imitating and accent on subsequent comprehension of sentences spoken in that accent.

In the experiment, Dutch volunteers were first tested on how well they understood sentences spoken in an unfamiliar accent of Dutch. To make sure that all listeners were unfamiliar, a new accent was invented for the study, in which all the vowels were swapped (for instance ‘ball’ would become ‘bale’). Next, each participant listened to 100 sentences in the unfamiliar accent. But first, they were given different instructions on how to respond to the sentences. Some were told to repeat the sentence, imitating the accent. Others were told either only to listen, to repeat the sentences in their own accent, or to transcribe the accented sentences as they had heard them, complete with strange vowels. Finally, the participants were tested again on how well they could understand sentences spoken in the unfamiliar accent.

People who had imitated the accent did much better at understanding the sentences than the other people. “When listening to someone who has a really strong accent, if you talked to them in their accent, you would understand better,” Adank says. Of course, she says, “it’s obvious that you can’t really do that.” If you put on, say, a fake Southern accent when talking to someone from Georgia, they might not think your intention is friendly. But when your brain subtly and unconsciously shifts your voice to sound more like theirs, it appears to be deploying a useful strategy.

Association for Psychological Science

FEAR OF BEING ENVIED MAKES PEOPLE BEHAVE WELL TOWARD OTHERS

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It’s nice to have success—but it can also make you worry that the jealous people will try to bring you down. New research in Psychological Science, a journal of the Association for Psychological Science, has found that the fear of being the target of malicious envy makes people act more helpfully toward people who they think might be jealous of them.

In previous research, Niels van de Ven of Tilburg University and his colleagues Marcel Zeelenberg and Rik Pieters had figured out that envy actually comes in two flavors: benign envy and malicious envy. They studied people who showed these two kinds of envy and found that people with benign envy were motivated to improve themselves, to do better so they could be more like the person they envied. On the other hand, people with malicious envy wanted to bring the more successful person down. Van de Ven and his colleagues wondered what the experience was like for the people who are the target of the envy.

“In anthropology, they say if you are envied, you might act more socially afterward because you try to appease those envious people,” van de Ven says—by sharing your big catch of fish, for example. They wanted to know if these observations from anthropology held up in the psychology lab.

In experiments, he and his colleagues made some people feel like they would be maliciously envied, by telling them they would receive an award of five euros—sometimes deserved based on the score they were told they’d earned on a quiz, sometimes not. The researchers figured the deserved prize would lead to benign envy, while the undeserved prize would lead to malicious envy. Then the volunteer was asked to give time-consuming advice to a potentially envious person.

People who had reason to think they’d be the target of malicious envy were more likely to take the time to give advice than targets of benign envy.

In another experiment, an experimenter dropped a bunch of erasers as the volunteer was leaving; those who thought they’d be maliciously envied were more likely to help him pick them up.

“This sort of serves a useful group function,” says van de Ven. We all think better off people should share with others, “but that’s not something we are inclined to do when we are better off.” This fear of envy can encourage us to behave in ways that improve the social interactions of the group.

Association for Psychological Science

UNDERSTANDING SHAPE-SHIFTING POLYMERS

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Shape-memory polymers are not a new discovery, as anyone who has played with Shrinky-Dinks or who has used heat-shrink tubing for wires in an electronic circuit can testify. But now, thanks to new analysis by researchers at MIT, the behavior of these interesting materials has been mathematically modeled in detail, which should make it easier to use the materials in new ways; potential applications include implantable biomedical devices and space structures that could be launched in a compact form and then unfurled once in orbit.

Shape-memory materials share an unusual property: They can be squished, twisted or bent into a variety of configurations, but when heated above some threshold temperature (for example, by being dunked in warm water or heated in an oven) they revert to the original shape in which they were made. Metal alloys such as nitinol (an alloy of nickel and titanium) were the first such materials studied, but polymer-based shape-memory materials have some significant advantages over the metal ones, says Lallit Anand, the Warren and Towneley Rohsenow Professor of Mechanical Engineering at MIT.

Anand and graduate students Vikas Srivastava PhD ’10 and Shawn Chester studied a representative shape-memory polymer material that can double in size; in contrast, nitinol can only increase in size by about 5 percent. This added capacity could allow the design of more complex geometries for applications, Srivastava says. In addition, the material itself is softer and has a rubbery consistency, and may be less likely to damage surrounding tissues when used in biomedical devices.

While shape-shifting polymers have been known for a few decades, until now there has been no detailed understanding of the basic molecular behavior responsible for the materials’ properties, and so trying to adapt them to any new application was essentially “all just trial and error,” Anand says. A numerical understanding of their behavior didn’t matter for applications such as heat-shrink tubing, but increasingly these materials are being harnessed for critical applications in biomedical devices, data-storage systems or self-deployable space structures that require great precision.

Srivastava says he believes that the numerical simulation he and his fellow researchers developed “will allow relatively accurate design of complex shape-memory polymer-based devices and systems,” and thus will bring such applications closer to becoming practical.

Some of the earliest work on designing biomedical devices using such materials was carried out by MIT Institute Professor Robert Langer but that work was done without the ability to model the material’s behavior accurately on a computer.

Now, Anand says he and his students have developed the theory and numerical simulation capability necessary to design various devices, by predicting their strains, forces and interactions. Moreover, he says, the simulations have been confirmed in laboratory tests. This should make it easier to optimize the designs of new applications.

One detailed simulation the team carried out was a design for a polymer-based stent, a device for keeping a blood vessel open. Their analysis and experimental verification were described in a paper published in August in the Journal of the Mechanics and Physics of Solids. Srivastava was the lead author, with Chester and Anand as co-authors. The work was supported by the National Science Foundation and the MIT-Singapore Alliance.

Ken Gall, a professor of materials science at Georgia Institute of Technology, who was not involved in this research, says, “This is no doubt the most comprehensive analysis published on the behavior of shape memory polymers.” He adds that it “will provide a means to assess proposed applications of the materials, and also motivate new applications.”

Although this work represents “a step on the path” to more widespread use of these materials, Anand says there remain some unanswered questions, such as the long-term durability of such structures when subjected to millions of cycles of deformation. Also, the analysis was focused on one specific composition out of a whole family of shape-memory polymers. Though the underlying materials-science characteristics should be similar and the formulas they developed are “reasonably general,” further studies will be needed to pin down any possible differences. “The work will continue,” he says.

(Photo: Vikas Srivastava and Shawn Chester)

MIT

TRIGGER THAT PREPARES ANIMALS FOR THE SEASON... WHATEVER THE WEATHER

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University of Manchester scientists have helped identify the key trigger mechanism in the ‘internal clocks’ of animals which means they are prepared for the season whether snow comes in November or the sun shines in March.

The research team, led by Dr Hugues Dardente and Professor David Hazlerigg at the University of Aberdeen and including Professor Andrew Loudon and Dr Sandrine Dupre at Manchester’s Faculty of Life Sciences, has pinpointed the ‘switch’ controlling seasonal hormone production, based on the changing daily cycle of light and darkness.

Their findings, published in Current Biology, give new insight into the link between daily and seasonal timing in mammals and suggest that an ancient mechanism has remained largely unchanged during vertebrate evolution. The extent to which such mechanisms are "hard-wired" will have a major impact on how animals cope with changing seasons in a warming world.

The study, in collaboration with the universities of Manchester and Edinburgh, looked at the primitive Soay breed of sheep, which relies on strong seasonal biology to survive in the wild on the North Atlantic islands of St Kilda.

The team identified the key signal to the brain controlling seasonal behaviour and physiology in a previous study in 2008. It found that a chemical known as thyroid stimulating hormone (TSH) acts in the brain to control the activation of seasonal breeding in sheep, and is regulated by day length. But the researchers did not know how changes in the daily cycle of light and dark triggered the production of high levels of TSH in the spring and a decline in the autumn.

Professor Loudon said: “We have now indentified that ‘switch’, linking the daily ‘circadian clock’ to the yearly seasonal clock. This reveals a potential genetic mechanism as to how local populations may adapt and is going to be crucial as we explore the implications of global climate change for timing of breeding and production of young.

“The evidence is that species in the high arctic are going to be in serious trouble, as they will not be able to adjust their annual clock to match altered local seasons.”

Professor Hazlerigg said: “"Understanding this process is vital as seasonal changes in day length are used by animals to synchronise major life-history events such as migration, moulting, and reproduction.

“It enables seasonal animals to anticipate and prepare biologically for what is going on in the outside world rather than adapting to it once it has happened, for example growing a thick coat in preparation for winter.

“Because the switch we describe is based on day length, it performs reliably, regardless of whether we have snow in November or an unseasonably warm March.”

This has important implications for the adaptation of strongly seasonal animals to climate change. Animals with systems that are highly reliant on day length as a cue may struggle to adapt as global warming starts to affect the timing of favourable conditions for growth and breeding. For example, a warm spring might lead to birds arriving at a spring feeding area after the peak of food availability has already passed, to the detriment of their breeding success. By defining the molecular pathways through which day length synchronisation operates, we open the way for genetic analyses of the impact on climate change on seasonal species, and may be able to predict species vulnerability dependent on habitat and genetic makeup.

(Photo: Loeske Kruuk)

University of Manchester

PALEOVIROLOGY EXPANDED: NEW VIRUS FRAGMENTS FOUND IN ANIMAL GENOMES

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Understanding the evolution of a virus can help beat it. This is immediately true in the fight against the ever-changing influenza bug, and potentially so in ongoing battles against Ebola and dengue fever, too. New research now points the way to a fossil record of viruses that have surprisingly insinuated themselves into the genomes of insects and animals, providing clues about their evolutionary history. The findings, to be published online by PLoS Genetics, could enable scientists to learn from genetic “fossils” of viruses in much the same way that they do from retroviruses, which unlike regular viruses, use their host’s genetic machinery to reproduce.

Robert Gifford, Aaron Diamond AIDS Research Center assistant professor at Rockefeller University, led the research, which used the rapidly advancing technology for genetic screening to analyze a database of insect, bird and mammal DNA for fragments of virus genomes, named endogenous viral elements (EVEs). Working with colleague Aris Katzourakis from the University of Oxford, he discovered representatives of ten families of viruses, including hepatitis B, Ebola, rabies and dengue and yellow fevers.

“This has really only become practical because of the scale of sequencing that’s been done,” Gifford says, referring to the reference genomes of the animals that he matched against those of different viruses. “In some cases, we’ve got the first evidence of an ancient origin for some of these virus groups.”

Since the 1970s, scientists have found the genetic signatures for retroviruses in animal genomes, a discovery explained by the fact that retroviruses (such as HIV) integrate into their hosts’ chromosomal DNA in the process of reproducing themselves. In humans, retrovirus fossils account for as much as eight percent of our DNA. This fossil record has allowed researchers to trace the ancestry of some of these viruses, and in some cases even determine what was responsible for killing them off.

The diversity of new viruses discovered in animal genomes includes the first endogenous examples of double-stranded RNA, reverse transcribing DNA and segmented RNA viruses, and the first DNA viruses in mammals. The findings suggest that scientists will eventually be able to recover genetic fossils for many, if not all virus families, greatly broadening the scope of paleovirological studies. “It’s the tip of the iceberg,” Gifford says.

Much remains to be learned about endogenous viral elements, including exactly how these virus fragments find their way into nuclear DNA. Most of the fragments documented by Gifford are no longer functional, appearing like what is commonly referred to as junk DNA. But Gifford says the findings suggest that some of these virus fragments have been co-opted by their hosts at some point in their evolutionary history, perhaps as a defense against related infections.

In particular, Gifford says that finding endogenous viral elements in insect genomes promises to reveal a new dimension in paleovirology, allowing scientists to probe the relationship and evolution of the virus, its vector and host, potentially providing insight into the complex ecological relationships that underpin insect-borne diseases.

Rockefeller University

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