Ever since neuroscientists discovered a decade ago that middle-aged and even old brains keep producing new neurons, they have puzzled over a fundamental question: are these new recruits good for anything, and if so, what?“Intuitively we feel that those new brain cells have to be good for something, but nobody really knows what it is,” said James (Brad) Aimone, a graduate student at the University of California, San Diego.

He and Fred Gage, who led the paradigm-changing discovery of adult neurogenesis (the paradigm being that we’re born with all the neurons we’ll ever have and it’s all downhill from there), have an intriguing suggestion. As they and Janet Wiles of the University of Queensland describe in a new paper in the journal Neuron, neurogenesis at the entryway to the hippocampus, a region of the brain that encodes memories, might help memory in several ways. New neurons of the same age might somehow tag incoming experiences—memories-to-be—that arrive at the same time in such a way that the memories remain forever linked, a process they call pattern integration. The newborn neurons might also tag new hippocampal memories with something like a date stamp, so you know what happened before and after other memories.

“By labeling contemporary events as similar, new neurons allow us to recall events from a certain period,” speculates Gage.

The reason this is speculative is that the suggestions arise from a computational model that Gage, a neurobiologist at the Salk Institute for Biological Studies, and his colleagues used to simulate circuitry in the hippocampus and the region that serves as its entryway, called the dentate gyrus. The scientists still need to study living brains.

But the possibilities are intriguing. Scientists know that newborn neurons make connections to mature brain cells and insinuate themselves into brain circuitry. Then a new crop of neurons is born, eventually joining the existing circuits, too. That sequence means that information reaching the dentate gyrus passes through new neurons of a particular generation, or class. As a result, information about events that occurred around the same time can be tied together by the common experience of passing through that generation of newborn neurons. So if you think back to a vacation, thinking of the hotel you stayed at will retrieve memories of the restaurants you visited and the sightseeing you did.

“Current thinking holds that when we bring up a certain memory, it passes back to the dentate gyrus, which pulls all related bits of information from their offsite storage,” says Gage. “Our hypothesis suggests that cells that were easily excitable bystanders when the memory was formed are engaged as well, providing a hyperlink between all events that happened during their hyperactive youth.”

If your collection of space photographs has some gaps, this is your chance to fill at least one of them.

NASA has invited the public to vote on the next celestial object for the Hubble Space Telescope to photograph. There are six candidates, including two planetary nebulae (unrelated the planets, they’re the gaseous remains of stars in their death throes), a star-forming region, a spiral galaxy (NGC 5172), an edge-on view of a spiral galaxy (NGC 4289) and two galaxies “interacting”—or, to the dramatically-inclined, about to collide.

As I write this, the impending mash-up is winning. Do space aficionados have the sensibility of rubber-neckers fascinated by car crashes?

It will be interesting to see what climate deniers make of this headline: New Study Shows Climate Change Largely Irreversible. If it is—irreversible, that is—then a reasonable response might be, so then why exactly am I being asked to conserve energy and buy a hybrid car and pay more for wind power . . . when we’re toast anyway?

The study, published in the current Proceedings of the National Academy of Sciences, comes from one of the nation’s leading climatologists, Susan Solomon of the National Oceanic and Atmospheric Administration (who also co-chaired the working group on the physical basis of climate change for the 2007 assessment of the Intergovernmental Panel on Climate Change). Solomon and her colleagues conclude that there’s no going back: changes in global temperature, rainfall, and sea level will be essentially irreversible for more than 1,000 years after we completely stop releasing carbon dioxide and other greenhouse gases into the atmosphere.

“It has long been known that some of the carbon dioxide emitted by human activities stays in the atmosphere for thousands of years,” Solomon said. “But the new study advances the understanding of how this affects the climate system.” Short answer: not for the better.

Current levels of CO² have reached 385 parts per million. Solomon’s study examined what happens if it reaches 450 to 600 ppm before emissions are halted. Chief among the lasting effects: irreversible decreases in dry-season rainfall in southern Europe, northern Africa, southwestern North America, southern Africa and western Australia, with results “comparable to those of the ‘dust bowl’ era,” write the scientists. The calculations also foresee “inexorable sea level rise” of up to 3 feet if we peak at 600 ppm and just under 6 feet if we go all the way to 1000 ppm. When rainfall decreases for periods not of decades but of centuries, human water supplies will fall, wildfires will become more frequent, ecosystems will change beyond recognition and deserts will expand.

The reason the climate impacts last so long is the world’s oceans. They act like an immense heat sink to “keep temperatures almost constant for more than a thousand years,” said Solomon.

The scientists conclude like this: “It is sometimes imagined that slow processes such as climate changes pose small risks, based upon the assumption that a choice can always be made to quickly reduce emissions and thereby reverse any harm within a few years or decades. We have shown that this assumption is incorrect for carbon dioxide emissions . . . . Irreversible climate changes due to carbon dioxide emissions have already taken place, and future carbon dioxide emissions would imply further irreversible effects on the planet.”

So, returning to the question about how society acts when experts conclude there’s no going back, I imagine this will undercut efforts to reduce greenhouse emissions, and perhaps increase support for geoengineering schemes that suck CO² out of the air, as I discussed in 2007. What may well get lost is this: although some changes are locked in, how bad those changes are depends on how many more millions of tons of greenhouse gases we load into the atmosphere.

If you’re out of ideas for a conversation over family dinner tonight, try this (it works better if you have a four-legged pet): how do cats and dogs walk? That is, in what order do the four legs take steps?

If your family is like most of us—and “us” includes, somewhat appallingly, illustrators for veterinary anatomy books as well as toy designers and the curators who put together dioramas at natural history museums—they’ll get it wrong. According to a sobering little paper in the January 27 issue of Current Biology, both laymen and people who should know better get the walking gait of horses and other quadrupeds (something  Eadweard Muybridge documented and published in the 1880s; the Wikipedia entry has nice videos) wrong about half the time.

The study, led by Gábor Horváth and György Kriska of Eötvös University in Hungary, explains why model horses fall over so often. They’re typically depicted in stride, but the wrong stride; horses, dogs, cats et al. ambulate the way they do because it provides the greatest stability. If a quadruped walked any other way, it would tip over . . . as model horses tend to.

And now the answer: in all four-legged animals, the order is: left hind leg, left foreleg, right hind leg, right foreleg. Repeat. Any leg can take the first step, but once it does the sequence is that above.

Oh, and while illustrators and museums and toy designers mess up, Jurassic Park and The Lord of the Rings got the gaits of dinosaurs, elephants and fantasy beasts exactly right.

On only the fourth day of his presidency, it’s obviously way too soon to assess whether Barack Obama’s effect on African-Americans will extend beyond providing hope and inspiration. Will he, for instance, goad black students to higher achievement, since he is living proof that working hard can pay off? One intriguing hint of what researchers led by Ray Friedman of the Vanderbilt Owen Graduate School of Management calls the “Obama Effect” suggests that maybe, just maybe, Obama will do more for the scholastic achievement of African-Americans than anything since Brown v. Board of Education.

In a paper under review at the Journal of Experimental Social Psychology, Friedman and colleagues present findings suggesting that Obama might close the black-white gap in scores on standardized tests. That gap reflects, in part, what psychologists call “stereotype threat”. In this now well-established phenomenon, being reminded that you belong to a group that, according to prevailing stereotypes, isn’t good at something causes you to do worse on a test of that something than if you were not so reminded. Similarly, if you are told that you are being assessed on something that stereotypes say your group is not good at (“girls can’t do math”) you do worse than it you’re told the test does not (in this example) detect gender differences. It’s easier to explain by example. When girls who are about to take a math test are reminded of their sex  (basically they just check M or F on a line asking their gender), or when African-Americans about to take a standardized test such as the SAT are reminded of their race, or even when white males take a test that they’re told Asians excel on, they do worse than otherwise. Apparently, students become so anxious about confirming the stereotype that their brains stumble. As the researchers write, “concern about confirming entrenched negative racial stereotypes via poor performance . . . ironically leads to their underperformance on challenging exams.”

So here’s what the new study did. At four different times during 2008 (late August, before the Democratic nominating convention; just after Obama’s acceptance speech; in early October; and right after election day), it asked about 120 college students to take an online test consisting of 20 questions from the Graduate Record Exams (GREs). (Over the four testing periods, 84 black students and 388 white students, matched for education levels, participated.) They were told that the exam was “created by the Massachusetts Aptitude Assessment Center, and is used as a diagnostic tool to assess verbal problem-solving ability”—a ruse meant to activate the stereotype that blacks don’t do as well as whites on aptitude tests. They also had to indicate their race before taking the exam, also known to activate stereotype threat.

The results varied according to when the students took the test. Before the convention and in early October, the performance gap was as wide as ever: white students got a median score of 12.1 compared to blacks’ 8.8 before the convention; the scores were 12.9 and 8.4, respectively, in early October. But just after Obama’s convention speech, and just after election day, “when Obama’s stereotype-defying accomplishments garnered national attention,” as the researchers put it, there was a remarkable effect. Among students who watched Obama’s speech, blacks’ and whites’ scores were statistically equal (10.3 vs. 12.1) after the acceptance speech and 9.8 vs. 11.1 after election day. The difference is considered statistically insignificant--that is, likely due to chance.

Here’s how the researchers see it: “The fact that we found effects with a random sample of American participants, far removed from any direct contact with Obama, attests to the impact that such a powerful role model can have. At the same time, this research provides evidence that real world role models, such as Obama, can trump racial stereotypes only when their success and accomplishments are especially salient. . . . Obama’s impact on Black-Americans’ performance may only occur when his success is highlighted”—that is, the performance gap vanished when his success sparked a media frenzy (acceptance speech, election) but not when it was less visible (pre-convention, early October).

Now the caveats. It is significant that the performance gap vanished in the wake of the acceptance speech only among black students who watched it. Among blacks who did not watch it, scores continued to lag those of whites. That raises the possibility that only some black students will benefit from Obama’s trailblazing. I asked Joshua Aronson of New York University, one of the founders of the research on stereotype threat, what he thought of the study. “They hypothesis [that Obama’s success might eliminate stereotype threat for blacks] makes a lot of sense,” he said. “Studies have shown that even a brief intervention [like watching Obama’s Denver speech] can nullify a stereotype. But the big problem is that . . . participants were not randomly assigned to condition; rather, they self-selected. There looms the strong possibility that the participants who chose to watch Obama's speech and chose to be in the study are the type of students who would be inspired by him and whose test performance would be boosted by thinking about him.” To be sure, there was no such self-selection for the final test condition, after the election; then, everyone knew that Obama had won, and the test-score gap also vanished.

Other experts nevertheless sounded a note of caution similar to Aronson’s, echoing the concern that the Obama Effect may only apply to a particular sub-population of African Americans. Clearly, more experiments need to be done. But the very possibility that Obama’s achievement will pull along an entire generation is intriguing.

And now the last holdout has succumbed: Antarctica had been the only one of the seven continents that measurements showed was not heating up, but a new analysis of the past 50 years, using more complete records than ever before, shows that the mercury has been rising on the southern continent, too.

Until now, scientists had recorded strong warming of the Antarctic Peninsula but slight cooling of the interior since the 1950s. The supposed cooling has delighted climate contrarians, such as the prolific Senate staffer (to “global warming is the biggest hoax” Sen. James Inhofe) Marc Morano, who has written, "Contrary to media hype, the vast majority of Antarctica has cooled over the past 50 years."

Unfortunately for anyone who still harbors hopes that the laws of atmospheric physics have been repealed, that is not the case. Previous temperature recordings have been skewed by the sparseness of weather stations in Antarctica (all but two are on the coasts rather than the continental interior) and the short duration of the observations. The most complete analysis to date, using weather-station data supplemented by satellite records and statistical models, is being reported this afternoon in Nature. It finds that “significant warming extends well beyond the Antarctic Peninsula to cover most of West Antarctica, an area of warming much larger than previously reported,” scientists led by Eric Steig of the University of Washington and Drew Shindell of NASA’s Goddard Space Flight Center.

The west Antarctic warmed 0.17 degree C. per decade since 1957—that is, 0.85 degree C. in 50 years—mostly in winter and spring. Although East Antarctica cools in the autumn compared to past decades, they find, “the continent-wide average near-surface temperature trend is positive,” warming about 0.12 degree C. per decade.

I look forward to the climate contrarians' arguments that this observed warming is a natural occurrence and has nothing to do with manmade greenhouse gases.

I hate to pour cold water on what seems like a surefire way to combat childhood obesity—namely, school-based health and exercise programs—so I’ll blame the Cochrane Collaboration for doing so. This non-profit group of scientists and physicians, based in England, regularly assesses the weight of the evidence on health and medical questions from whether St. John’s wort can alleviate depression (yes, sort of) to whether mouthwash can reduce bad breath (in some cases). Now the Cochrane team has weighed in on whether school programs can help kids lose weight and inspire them to exercise more. Answer: no, on both counts.

That’s a little discouraging, given the renewed emphasis on using schools to combat the growing incidence of childhood obesity and its attendant diabetes. Studies from Greece to England to Australia and beyond have looked for correlations between physical inactivity and obesity, or school-based exercise programs and health benefits, calling almost unanimously for (to pick just one) “necessary school interventions in order to encourage healthier behaviours and habits.” To be sure, school-based programs here and there have reported success in reducing obesity and fostering healthy habits, but the results tend to be equivocal, especially when it comes to getting kids to stick with the program.

Taken together, the 26 studies of school-based programs aimed at promoting physical activity in Australia, South America, Europe and North America which the Cochrane team examined increased how long children spend exercising and cut their TV-watching time. So far, so good. The programs also reduced blood cholesterol levels and improved lung capacity, a measure of fitness. But—now the bad news—the programs had little effect on weight or blood pressure or on what kids choose to do in their free time, the last being a crucial indication of whether the programs are likely to change lifestyle habits for the better.

“Given that there are at least some beneficial effects, we would recommend that schools continue their health promotion programs,” said Maureen Dobbins of the School of Nursing at McMaster University in Ontario, who led the review.

But why didn’t the programs do what public health officials hope, namely take off pounds and instill lifelong healthy habits? “Physical activity classes may be too closely associated with school work, so for some students this makes them feel like they are being made to do more work,” says Dobbins. In that case, the last thing kids want to do is more such “work” on their own time, when a teacher isn’t making them. Kind of like if you make reading a chore for kids, they think of it that way—and never want to pick up another book unless they have to.

It was probably inevitable. With the growing use of preimplantation genetic diagnosis (PGD) , in which embryos created by in vitro fertilization are screened for genetic defects, the day was going to come when fertility doctors used it not for the well-established purpose of identifying glitches thatinvariably lead to disease—mutations such as those causing hemophilia, fragile X syndrome, neuromuscular dystrophies, Rett syndrome, cystic fibrosis, Tay-Sachs, sickle-cell anemia and Huntington disease. Instead, PGD was also going to be used to look for mutations that onlymight lead to problems. Doctors announced that the first baby screened for the breast- and ovarian-cancer gene BRCA1 was born in Britain.

Granted, this was in a family who, doctors said, had had three generations of women stricken with breast or ovarian cancer in their 20s. The family’s desire to spare their baby girl a similar fate is understandable. As Paul Serhal, Medical Director of the Assisted Conception Unit where the diagnosis took place, said, “This little girl will not face the specter of developing this genetic form of breast cancer or ovarian cancer in her adult life. The parents will have been spared the risk of inflicting this disease on their daughter. The lasting legacy is the eradication of the transmission of this form of cancer that has blighted these families for generations.”

But here’s the rub. The risk of developing breast cancer if you have a mutation in BRCA1 is very likely not the oft-quoted 82%. In late 2004, scientists led by Sholom Wacholder of the National Cancer Institute went public with long-simmering concerns about the 2003 study that established (in the mind of the public and doctors, though not geneticists well-versed in the pitfalls of this kind of study) the risk of breast cancer conferred by carrying mutations in BRCA1: an 82% chance of developing breast cancer by age 80, compared to 12% for women overall.

As Wacholder and his colleagues pointed out, that estimate is much higher than what other studies of women with the mutations have found—46% in one, for instance, with other estimates in the range of 50% to 60%. The study that yielded the higher estimate, Wacholder told me in 2005, contained serious flaws.

In a nutshell, it recruited cancer patients and then examined their DNA for BRCA1 mutations. But that means that people with the mutationsand no cancer were excluded from the analysis. That would inflate the risk estimate. (How might you have the "bad" form of BRCA1 and not develop breast cancer? Presumably because other genes undo whatever damage BRCA1 mutations do.)

“This is not a small disagreement, such as whether the true risk is 90% or 95%,” Wacholder said. “The disagreement is whether the true risk is closer to 50% or to 80%. That’s the difference between a coin flip and a virtually-sure thing.”

Just to repeat, in the case of the British family their BRCA1 mutation plus genetic background seemed to make breast cancer as close to a sure thing as you can get. But what of the countless other families without this history? If we start screening for mutations that might or might not bring on disease, and discarding those embryos that don’t make the cut, let’s at least acknowledge what we’re doing: an unprecedented experiment in directing human evolution. Will families demand PGD for genes associated with risk-taking? neuroticism? marital infidelity? Do they care that most such gene-disease links have failed to hold up, and that the track record of genes and behavior is even worse? I'm betting not. The desire for the perfect, flawless baby will not be thwarted by science, let alone logic.

When scientists in England reported last April that what a woman eats around the time she conceives can affect whether she has a boy or a girl—the headline-making finding of the study, titled “You Are What Your Mother Eats,” was that women who ate breakfast cereal were more likely to have a boy—it was picked up by more newspapers and Websites than you can count (including here, here and here). Basically, they reported that 56 percent of women who consumed the most calories (including breakfast cereal) before conceiving had boys, while only 45 percent of women who consumed the fewest calories did. Now comes the not-so-fast part.

In a paper online in the same journal that published the original, scientists led by statistician S. Stanley Young, assistant director of the National Institute of Statistical Sciences, call the link between eating cereal and giving birth to a boy “most likely a multiple testing false positive.” They contend that the correlation between eating cereal and having a boy is easily explained by chance, and is not a true cause-and-effect relationship.

The statistical argument is somewhat arcane, but can be boiled down to this: if you test lots and lots of things (behaviors, genes, anything) to see whether it is correlated with some outcome (getting a disease, having a boy, whatever) then you are bound to get a hit by chance alone. Think of it this way: you are curious about whether particular articles of clothing correlate with getting run over by a car, and you test hundreds of clothes (pink shirts, blue shirts, black pants, blue jeans, do-rags, cowboy hats . . . ). By statistical fluke, people wearing some article of clothing are going to be more likely to get run over than are people wearing any other article of clothing. Look at enough pairings of supposed cause and effect, and by chance alone you’ll find one.

“Multiple testing can easily lead to false discoveries,” write Young and his co-authors. “Hundreds of comparisons were conducted . . . [so] the claimed effects are readily explainable by chance.”

The authors of the original paper, led by Fiona Mathews of the University of Exeter, are having none of it. They deny running hundreds of tests in a search for something that correlates with sex determination. Firing back, they say that their critics' “account of our work bears little relationship to the methods, results or conclusions we report. For example, [they] claim that we used 396 tests to address our primary hypothesis. In fact, we used two.” (Young disputes this. How many tests Mathews ran depends on what you mean by “tests.” And, probably, by “how many.”)

While we let the two teams duke it out, I am reminded of the cautionary note that John Ioannidis of Tufts University and the University of Ioannina School of Medicine (in Greece) sounded in 2005. The title of his paper, “Why Most Published Research Findings Are False,” says it all.

With state and municipal budgets bleeding red ink, programs from Medicaid to after-school activities are on the chopping block, at least until (unless?) the feds come to the rescue with a stimulus plan. It’s impossible to rank the saddest losses, but I admit to a soft spot for the zoos, aquariums and botanical gardens here in New York.

In fiscal year 2009 (which runs from April 1, 2008 to the end of March 2009), they were supposed to divvy up $9 million from the state's environment fund, but Gov. David Patterson, facing the largest budget gap in New York’s history, proposed cutting that to $4 million (with the result that some of the institutions promised some of the ’09 money have yet to receive their check, and have—in good faith—spent at least part of what they were promised starting 10 months ago). Even worse, Patterson proposed zeroing out the money in the fiscal year starting April 1, 2009.

How will zoos cope? Unlike a museum, which can close a wing or two to save on utility and security costs, zoos can’t simply shut down part of their operations: animals have to eat and get veterinary care, and plants need to be tended, or they’ll die. “We can’t furlough our sea lions,” one official of the Wildlife Conservation Society, which runs the Bronx Zoo (2008 operating budget: $67 million), New York Aquarium (2008 operating budget: $15 million) and other sites (which get 12 million visitors a year), told me.

WCS is hoping to enlist public support to keep its state funding, with a clever video (produced in house) that will bring a smile to your lips. You can find it here. Whether it also makes you open your wallet or write your state rep to protest the plan to cut off the zoo, I leave to you.

If you are a fan of science news, then odds are you are also intrigued by brain imaging, the technique that produces those colorful pictures of brains “lit up” with activity, showing which regions are behind which behaviors, thoughts and emotions. So maybe you remember these recent hits: which regions of the brain listen to angry voices, which regions are active when women grieve the break-up of a romantic relationship, activity showing the problems cocaine addicts have in responding to rewards, how social rejection increases activity in the same brain regions as physical pain, how men and women show different brain activation patterns when they think about their partner cheating on them sexually (men: regions involved in sexual and aggressive behaviors such as the amygdala and hypothalamus become more active) or emotionally, which brain regions become more active when arachnophobes think about spiders, which regions become active when you first experience intense romantic love  . . .  the list goes on and on and on. And now a bombshell has fallen on dozens of such studies: according to a team of well-respected scientists, they amount to little more than voodoo science.

The neuroscience blogosphere is crackling with–so far—glee over the upcoming paper, which rips apart an entire field: the use of brain imaging in social neuroscience, which studies how the brain processes/produces/handles the social and emotional aspects of human behavior such as jealousy, grief and altruism. This field includes stuff like the above, and has exploded in the last 10 years as psychiatrists and social psychologists became enamored of fMRI and other brain imaging toys. (My guess: like so many researchers in the social sciences, they have physics envy, and think that the illusory precision and solidity of neuroimaging can give their field some rigor.)

The new paper (to be published in Perspectives on Psychological Science but available here) is called “Voodoo Correlations in Social Neuroscience,” which gives you a pretty good idea of its argument. Basically, the authors noticed that a lot of papers in social neuroscience that use brain imaging were reporting correlations between brain activity and social/emotional behavior or thoughts that looked too good to be true or, even, mathematically possible (kind of like the years of steady investment returns that Bernie Madoff reported). So the scientists, led by Edward Vul of MIT and Harold Pashler of the University of California, San Diego, picked 54 such studies, many of them published in prominent journals such as Science and Nature, and wrote to the authors, basically asking how they managed to get such impressive correlations.

More than half admitted using a statistical strategy that, write Vul and his colleagues, “grossly inflates correlations, while yielding reassuring-looking scattergrams.” Other statistical snafus, they say, “likely created entirely spurious correlations in some cases,” and they call on social neuroscientists who use fMRI to reanalyze their raw data “to correct the scientific record.”

What’s striking about the discredited papers—though in fairness, the skewered authors should be given a chance to defend themselves—is how blithely they tend to (as mutuallyoccluded put it) “vindicate the crudest of stereotypes—that women love shopping because they’re “gatherers”, that girls have different kinds of brains and need to be taught separately, that gay men and straight women read maps similarly.” If you were wondering how, exactly, problematic studies got past the peer review at these top journals, that’s a clue: scientists no less than other mortals love to have their hunches, prejudices and stereotypes validated by empirical evidence. Maybe they didn’t look too critically at studies that did exactly that.

So there you are, sitting in a tiny waiting room with one white man and one African-American. The latter suddenly says, oh no, I left my cell phone in my car, leaps up and walks to the door, lightly bumping against the knees of the white man. When the African-American is out of the room the white man says, “Typical. I hate it when black people do that.”

How would you react? How would you feel? Would those feelings translate into any action, perhaps affecting which of the two—the white man who made a racist remark or the African-American who brushed against him—you would choose to partner with if you had to do a two-person job?

How about if the white man said something else when he was bumped—such as “clumsy n*****!”

When scientists recently ran just such an experiment (the white man and black men were in on the study; a third, white person in the room observing all this was the actual experimental subject), people's actual reactions were nothing like what they were forecast to be.

Even though racist comments can get you fired, ostracized or booted out of elected office, blatant acts of racism happen all the time. (This morning I woke up to news on the case of white teens who, furious over Obama’s win, went on an Election Day rampage against blacks on Staten Island ). So here’s the puzzle: if many (most?) people condemn racism, why do we let it persist? The experiment being published today in Science hints that although we like to think that we'd be upset over racism and even act on that feeling, in fact we kinda don’t care all that much.

The study was set up as I describe above. Volunteers witnessed a black student bumping into a white one (again, both students were actually part of the experimental team, acting out their assigned roles), and the white student reacting with a mild (“typical”) or extreme (“n*****”) racial outburst. In a few minutes the black student returned, followed by a scientist who asked all three to, first, complete a survey that asked about their current emotional state, and then asked the real participant to pick one of the two actors as a partner to solve a bunch of anagrams. For comparison, the scientists also had a separate group of white students read a description of the bump and the racist outburst, or watch a video of it, and to then predict how they would feel if they were in the room where it happened and which of the two possible partners—the racist white student or the clumsy black one—they’d pick for their anagram partner.

People who read about the interaction or saw it on video and predicted how they would feel if they were in the room when it happened reported feeling twice as upset (on a self-rating scale of emotions) as people who actually witnessed it. Just 10 or 20 percent predicted that, if they had been in the room, they would pick the white racist student as their anagram partner—but of the people who really were in the room fully 60 percent opted to partner with the student making the racist outburst.

It's worth quoting the scientists at some length. “People may erroneously believe that they would reject a racist in part because they overestimate the emotional distress that a racist comment would evoke,” write the scientists, led by John Dovidio of Yale and Kerry Kawakami of York University. “People’s predictions regarding emotional distress and behavior in response to a racial slur differ drastically from their actual reactions. Whereas participants who imagined themselves in the situation anticipated being very upset and distancing themselves from a person who made a racist comment, those who experienced this event did not.” Remarkably, this was so even when the comment included the racial slur considered one of the most offensive words you can utter.

In part, this disconnect between how badly people expect to feel about a racist incident and how they actually react reflects the well-established fact that people stink at predicting how they will react emotionally to something—including, apparently, racism. We think we’ll be upset and righteously indignant. But when we actually witness it? Not so much. That suggests that racism may persist because people who convince themselves that they would take action in the face of racism actually respond with indifference.

A caveat is in order. As with many psych experiments, this was an artificial, contrived situation. The volunteers knew they were in an experiment. It’s therefore possible that when they heard the racist comment, they thought of it as just “an unusual occurrence in the experimental context, able to be reinterpreted or minimized, and so eliciting little negative emotion or action,” as Elliot Smith of Indiana University and Diane Mackie of UC Santa Barbara point out in a commentary.

But that raises the obvious question. In real life, how often do we similarly “reinterpret” or otherwise excuse racism or sexism or other unacceptable behavior, therefore conveniently absolving ourselves of the responsibility to respond?

Looking back, it was pretty dumb to think that people got to the Americas from Asia once, or that a single group braved the ice bridge to the new world. A cool new study published online today in the journal Current Biology may bury that simplistic assumption once and for all: according to the evidence of mitochondrial DNA, the first Americans arrived in at least two separate migrations, at about the same time, about 15,000 to 17,000 years ago.

To be fair, anthropologists have been tiptoeing up to the idea of multiple migrations for a while. When scientists at the Center for the Study of the First Americans recalculated the age of the Clovis culture, named for a characteristic tool technology and considered to be the oldest irrefutable evidence of humans in the Americas, they got dates of 11,050 to 10,800 years ago—a range implying that “humans already lived in the Americas before Clovis” (since non-Clovis sites are older than that). And as far back as 2004, anthropologist Theodore Schurr of the University of Pennsylvania wrote that while the first migrants from Siberia crossed over to North America 20,000 to 14,000 years ago, probably following a coastal route, “a second migration that may have come from the same Siberian region entered the Americas somewhat later, possibly using an interior route.”

New genetic evidence makes that case more solid. Although the human genome project hasn’t been the promised godsend for human health and medicine (that link is to a 2005 article, but nothing much has changed in three years), it’s definitely been a boon to studies of human evolution and prehistory.

The new genetic analysis looks at mitochondrial DNA, which is passed from mothers to their children. Specifically, it looks at two rare mitochondrial DNA types that share a maternal ancestor. People carrying the type called D4h3 entered North America from Siberia and hugged the Pacific coastline, from which ice had mostly disappeared after the glacial maximum, the scientists conclude; they eventually reached Tierra del Fuego. People carrying the other mitochondrial form, X2a, set off inland, following a land corridor between two ice sheets which led them into the region east of the Rocky Mountains. They remained in North America. These first Americans were the ancestors of almost all modern Native Americans in North, Central, and South America (but not the Na-Dene or the Eskimos-Aleuts of the arctic).

“Two almost concomitant paths of migration . . . about 15,000 to 17,000 years ago led to the dispersal of Paleo-Indians, the first Americans,” said Antonio Torroni of the University of Pavia in Italy, who led the study (he made a splash last year when another genetic analysis suggested that a mere six women in the migration were the ancestors of all the Native Americans). That means the most likely scenario is that, within a few centuries, there were several arrivals into the Americas from Siberia. Did the earliest arrivals send back a scout to tell the stay-at-homes that this new world was worth a look? Did difficult conditions or population pressure in Siberia nudge people to seek greener pastures?

It’s too soon to load Tetris onto the equipment that soldiers carry into battle, but there’s an intriguing hint that playing that geometric game might act as what scientists are calling a “cognitive vaccine” against the horrible flashbacks that characterize post-traumatic stress disorder (PTSD), which more and more of those returning home from Iraq and Afghanistan are suffering.

The idea of using Tetris to vaccinate soldiers against PTSD rests on two facts. One, the brain has a finite processing capacity for each of two kinds of information: sensory/visual/spatial and narrative/meaning. Two, there is a window of about 6 hours to disrupt memory consolidation. What this implies, scientists led by Emily Holmes of the University of Oxford write in a new paper in the open-access journal PLoS One, is that a sufficiently demanding visuospatial task will keep the brain from retaining other spatial/visual information--that is, images, including traumatic ones. Tetris should be such a task, since recognizing the shapes and moving the blocks around places demands on the brain’s spatial-processing channel.

“Visuospatial tasks post-trauma, performed within the time window for memory consolidation,” write the scientists, should “reduce subsequent flashbacks.” But importantly, the narrative and meaning of the events should be unaffected, since that is a separate processing channel: people should remember that they witnessed or experienced a trauma, but should not be besieged by vivid visual images of it.

To test their idea, the scientists had 40 volunteers, aged 18 to 47, watch a 12-minute film showing such traumatic events as graphic scenes of actual surgery, fatal road traffic accidents and drowning. After a 30-minute break, half the volunteers played Tetris for 10 minutes and half did not. The scientists then had them keep a daily diary, noting when they had a flashback to any of the awful images in the film.

The initial results were promising. Playing Tetris soon after viewing the gory film clips reduced the number of flashbacks the volunteers had from just over 6 to about 3. It really did look as if the visuospatial demands of Tetris blocked the consolidation of the traumatic visuospatial memories. (Tetris should not interfere with memories for new facts, but you should probably think twice before playing it right after you tried to memorize a map or something else with a lot of visual or spatial content.)

“This is only a first step in showing that this might be a viable approach to preventing PTSD,” said Holmes. “We wanted to find a way to dampen down flashbacks—that is, the raw sensory images of trauma that are over-represented in the memories of those with PTSD. Tetris may work by competing for the brain’s resources for sensory information. We suggest it specifically interferes with the way sensory memories are laid down in the period after trauma and thus reduces the number of flashbacks.”

Newborn stars? Planets beyond our solar system? Black holes? The annual meeting of the American Astronomical Society has these and every other (it seems) denizen of the universe, but I have to mention three among my favorites of the discoveries being presented:

Our Milky Way galaxy is heavier, moving faster and therefore more likely to smack into its nearest neighbor than astronomers thought. Precision measurements of the Milky Way show that the galaxy is rotating about 100,000 miles per hour faster than previously understood, said Mark Reid of the Harvard-Smithsonian Center for Astrophysics—so here in our part of the galaxy, our little solar system is moving at about 600,000 miles per hour rather than the previously estimated 500,000 miles per hour.

The additional rotational velocity implies that the Milky Way’s mass is half-again as great as what had been thought, making it just about as hefty as the Andromeda Galaxy. “No longer will we think of the Milky Way as the little sister of the Andromeda Galaxy in our Local Group family,” said Reid. That extra mass means the Milky Way exerts a greater gravitational pull, which in turn makes it more likely that we will collide with Andromeda or smaller galaxies.

The scientists used the Very Long Baseline Array, a system of 10 radio telescopes stretching from Hawaii to New England to the Virgin Islands, to map the Milky Way in great detail—specifically, the distances to and motions of various regions of it. That brought another surprise: our galaxy probably has four, not two, spiral arms of gas and dust where stars are forming, as you can see in this cool artist’s rendition.

A third discovery addresses the conundrum of how young stars manage to exist in the center of the Milky Way. Logically, they either formed there or fell there. Two problems: the black hole at the galactic center produces such strong gravitational tides that any nearby stellar maternity wards (molecular clouds) should be ripped apart, preventing stars from forming. Yet stars falling inward after forming elsewhere is a rare occurrence.

Using the Very Large Array of 27 radio telescopes in New Mexico, astronomers led by Elizabeth Humphreys of the Harvard-Smithsonian Center for Astrophysics spied two protostars 7 and 10 light-years from the galactic center. That means starscan form there, despite the proximity of a black hole that gobbles everything it can reach. “We literally caught these stars in the act of forming,” said Humphreys.

I'm filing this under the heading "e-mails I wished I never opened."

Foe decades the innocuous words “artificial colors” or “color added” has been allowed to hide the presence of—sorry, but there’s no way to soften the blow here—insects in foods. The U.S. Food and Drug Administration has long allowed food- and cosmetics-manufacturers to use those phrases on their ingredient labels when the ingredient is carmine or cochineal, which are extracted from the dried bodies of the cochineal insect. But in a decision published yesterday, the FDA has ruled that carmine and cochineal have to be named.

The action comes 10 years after a consumer group, the Center for Science in the Public Interest, petitioned the agency to require the labels.

If you want to avoid eating insects because you’re a vegetarian, or because you’re Jewish or Muslim, or . . . well, just because, now the ingredients list will tip you off to what to avoid. (Also, a few people have reported allergic reactions to the ingredients.) Carmine and cochineal tend to be in reddish foods and drinks, including fruit drinks, ice cream, yogurt, and candy. And, yes, we all know that foods from flour to cereals can be contaminated with insect parts, but that's accidental. When the little buggers are in there on purpose, I want to know.