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Science Tuesday - Salt, Lizards, Lamarckianism?, and the science of touch
Findings: When It Comes to Salt, No Rights or Wrongs. Yet.
By JOHN TIERNEY, The New York Times, February 23, 2010
Suppose, as some experts advise, that the new national dietary guidelines due this spring will lower the recommended level of salt. Suppose further that public health officials in New York and Washington succeed in forcing food companies to use less salt. What would be the effect?
A) More than 44,000 deaths would be prevented annually (as estimated recently in The New England Journal of Medicine).
B) About 150,000 deaths per year would be prevented annually (as estimated by the New York City Department of Health and Mental Hygiene).
C) Hundreds of millions of people would be subjected to an experiment with unpredictable and possibly adverse effects (as argued recently in The Journal of the American Medical Association).
D) Not much one way or the other.
E) Americans would get even fatter than they are today.
Don’t worry, there’s no wrong answer, at least not yet. That’s the beauty of the salt debate: there’s so little reliable evidence that you can imagine just about any outcome. For all the talk about the growing menace of sodium in packaged foods, experts aren’t even sure that Americans today are eating more salt than they used to.
When you don’t know past trends, predicting the future is a wide-open game.
My personal favorite prediction is E, the further fattening of America, but I’m just guided by a personal rule: Never bet against the expansion of Americans’ waistlines, especially not when public health experts get involved.
The harder the experts try to save Americans, the fatter we get. We followed their admirable advice to quit smoking, and by some estimates we gained 15 pounds apiece afterward. The extra weight was certainly a worthwhile trade-off for longer life and better health, but with success came a new challenge.
Officials responded by advising Americans to shun fat, which became the official villain of the national dietary guidelines during the 1980s and 1990s. The anti-fat campaign definitely made an impact on the marketing of food, but as we gobbled up all the new low-fat products, we kept getting fatter. Eventually, in 2000, the experts revised the dietary guidelines and conceded that their anti-fat advice may have contributed to diabetes and obesity by unintentionally encouraging Americans to eat more calories.
That fiasco hasn’t dampened the reformers’ enthusiasm, to judge from the growing campaign to impose salt restrictions. Pointing to evidence that a salt-restricted diet causes some people’s blood pressure to drop, the reformers extrapolate that tens of thousands of lives would be saved if there were less salt in everybody’s food.
But is it even possible to get the public to permanently reduce salt consumption? Researchers have had a hard enough time getting people to cut back during short-term supervised experiments.
The salt reformers say change is possible if the food industry cuts back on all the hidden salt in its products. They want the United States to emulate Britain, where there has been an intensive campaign to pressure industry as well as consumers to use less salt. As a result, British authorities say, from 2000 to 2008 there was about a 10 percent reduction in daily salt consumption, which was measured by surveys that analyzed the amount of salt excreted in urine collected over 24 hours.
But the British report was challenged in a recent article in The Clinical Journal of the American Society of Nephrology by researchers at the University of California, Davis, and Washington University in St. Louis. The team, led by Dr. David A. McCarron, a nephrologist at Davis, criticized the British authorities for singling out surveys in 2008 and 2000 while ignoring nearly a dozen similar surveys conducted in the past two decades.
When all the surveys in Britain are considered, there has been no consistent downward trend in salt consumption in recent years, said Dr. McCarron, who has been a longtime critic of the salt reformers. (For more on him and his foes, go to nytimes.com/tierneylab.) He said that the most notable feature of the data is how little variation there has been in salt consumption in Britain — and just about everywhere else, too.
Dr. McCarron and his colleagues analyzed surveys from 33 countries around the world and reported that, despite wide differences in diet and culture, people generally consumed about the same amount of salt. There were a few exceptions, like tribes isolated in the Amazon and Africa, but the vast majority of people ate more salt than recommended in the current American dietary guidelines.
The results were so similar in so many places that Dr. McCarron hypothesized that networks in the brain regulate sodium appetite so that people consume a set daily level of salt. If so, that might help explain one apparent paradox related to reports that Americans are consuming more daily calories than they used to. Extra food would be expected to come with additional salt, yet there has not been a clear upward trend in daily salt consumption evident over the years in urinalysis studies, which are considered the best gauge because they directly measure salt levels instead of relying on estimates based on people’s recollections of what they ate. Why no extra salt? One prominent advocate of salt reduction, Dr. Lawrence Appel of Johns Hopkins University, said that inconsistent techniques in conducting the urinalysis surveys may be masking a real upward trend in salt consumption.
But Dr. McCarron called the measurements reliable and said they could be explained by the set-point theory:
As Americans ate more calories, they could have eased up on some of the saltier choices so that their overall sodium consumption remained constant. By that same logic, he speculated, if future policies reduce the average amount of salt in food, people might compensate by seeking out saltier foods — or by simply eating still more of everything.
The salt reformers dismiss these speculations, arguing that with the right help, people can maintain low-salt diets without gaining weight or suffering other problems. But even if people could be induced to eat less salt, would they end up better off? The estimates about all the lives to be saved are just extrapolations based on the presumed benefits of lower blood pressure.
If you track how many strokes and heart attacks are suffered by people on low-salt diets, the results aren’t nearly as neat or encouraging, as noted recently in JAMA by Michael H. Alderman, a hypertension expert at Albert Einstein College of Medicine. A low-salt diet was associated with better clinical outcomes in only 5 of the 11 studies he considered; in the rest, the people on the low-salt diet fared either the same or worse.
“When you reduce salt,” Dr. Alderman said, “you reduce blood pressure, but there can also be other adverse and unintended consequences. As more data have accumulated, it’s less and less supportive of the case for salt reduction, but the advocates seem more determined than ever to change policy.”
Before changing public policy, Dr. Alderman and Dr. McCarron suggest trying something new: a rigorous test of the low-salt diet in a randomized clinical trial. That proposal is rejected by the salt reformers as too time-consuming and expensive. But when you contemplate the potential costs of another public health debacle like the anti-fat campaign, a clinical trial can start to look cheap.
Observatory: Puzzle Solved: How a Fatherless Lizard Species Maintains Its Genetic Diversity
By SINDYA N. BHANOO, The New York Times, February 23, 2010
More than 40 years ago, Bill Neaves, then a young Ph.D. student, discovered how an all-female, asexual species of the whiptail lizard came to be. He found that the lizard was a cross between the female species of one type of lizard and the male species of another.
But what has puzzled him for years is how this all-female species maintains its high level of genetic variation, a contribution to evolutionary fitness that typically comes from sexual reproduction.
Despite reproducing without a male partner, this lizard species has a strong presence in the wild. Now, Aracely Lutes, a graduate student at the Stowers Institute for Medical Research in Kansas City, Mo., where Dr. Neaves works, has figured out the missing piece of the puzzle. The findings were reported Sunday in the journal Nature.
In a sexually reproducing lizard species, each lizard has 23 chromosomes from its mother, and 23 from its father.
During reproduction in the all-female species, Ms. Lutes found, all 46 of the mother’s chromosomes are duplicated, resulting in 92 chromosomes in each egg cell.
Those chromosomes then pair with their identical duplicates, and after two cell divisions, a mature egg with 46 chromosomes is produced. Since crossing-over during the cell divisions occurs only between pairs of identical chromosomes, the lizard that develops from the unfertilized egg is identical to its mother.
Importantly, each new lizard is also a replication of the original. Since the original was genetically diverse, pulling its chromosomes from two different species, its carbon copy descendants are, too.
It is because of this that the species has thrived over the generations. But unlike sexually reproducing species, these lizards will probably never evolve into a stronger species, Dr. Neaves said.
They “may be really well suited for the desert Southwest,” he said, “but when the next ice age comes, it may be that all of them get wiped out.”
Observatory: Crickets Warn Young Before Birth of Dangers of Wolf Spiders
By SINDYA N. BHANOO, The New York Times, February 23, 2010
If an expectant mother knew that dangerous creatures lurked around her, and knew also that she wouldn’t be around to take care of her young, she might be stressed.
And if she had a way to warn her young before they were born, surely she would.
Human mothers cannot do this, to the best of our knowledge. But pregnant crickets, it appears, do have the ability to forewarn. This is especially useful since crickets abandon their young after birth.
Researchers from the University of South Carolina Upstate and Indiana State University placed pregnant crickets in an enclosure where they were stalked, but not eaten, by a wolf spider, whose fangs had been coated with wax to protect the crickets.
The young of the spider-exposed mothers turned out to be more predator-savvy than those with mothers who were not exposed to the wolf spider; they stayed hidden longer, and were more likely to freeze when they encountered spider feces or spider silk.
In a second experiment, the researchers placed the juvenile crickets in an arena with a starving wolf spider with fully functioning fangs. Eventually, the spider got all the crickets, but the young born from spider-exposed mothers lasted longer in the arena of death.
The research was published last month in The American Naturalist.
What remains unclear is exactly how the crickets are warning their unborn. “We don’t know a specific mechanism,” said Jonathan Storm, a professor at the University of South Carolina Upstate in Spartanburg and one of the authors of the paper.
Although it is conjecture at this point, he said, “It’s possible that there could be some sort of hormone transmitted.”
Mind: Evidence That Little Touches Do Mean So Much
By BENEDICT CAREY, The New York Times, February 23, 2010
Psychologists have long studied the grunts and winks of nonverbal communication, the vocal tones and facial expressions that carry emotion. A warm tone of voice, a hostile stare — both have the same meaning in Terre Haute or Timbuktu, and are among dozens of signals that form a universal human vocabulary.
But in recent years some researchers have begun to focus on a different, often more subtle kind of wordless communication: physical contact. Momentary touches, they say — whether an exuberant high five, a warm hand on the shoulder, or a creepy touch to the arm — can communicate an even wider range of emotion than gestures or expressions, and sometimes do so more quickly and accurately than words.
“It is the first language we learn,” said Dacher Keltner, a professor of psychology at the University of California, Berkeley, and the author of “Born to Be Good: The Science of a Meaningful Life” (Norton, 2009), and remains, he said, “our richest means of emotional expression” throughout life.
The evidence that such messages can lead to clear, almost immediate changes in how people think and behave is accumulating fast. Students who received a supportive touch on the back or arm from a teacher were nearly twice as likely to volunteer in class as those who did not, studies have found. A sympathetic touch from a doctor leaves people with the impression that the visit lasted twice as long, compared with estimates from people who were untouched. Research by Tiffany Field of the Touch Research Institute in Miami has found that a massage from a loved one can not only ease pain but also soothe depression and strengthen a relationship.
In a series of experiments led by Matthew Hertenstein, a psychologist at DePauw University in Indiana, volunteers tried to communicate a list of emotions by touching a blindfolded stranger. The participants were able to communicate eight distinct emotions, from gratitude to disgust to love, some with about 70 percent accuracy.
“We used to think that touch only served to intensify communicated emotions,” Dr. Hertenstein said. Now it turns out to be “a much more differentiated signaling system than we had imagined.”
To see whether a rich vocabulary of supportive touch is in fact related to performance, scientists at Berkeley recently analyzed interactions in one of the most physically expressive arenas on earth: professional basketball. Michael W. Kraus led a research team that coded every bump, hug and high five in a single game played by each team in the National Basketball Association early last season.
In a paper due out this year in the journal Emotion, Mr. Kraus and his co-authors, Cassy Huang and Dr. Keltner, report that with a few exceptions, good teams tended to be touchier than bad ones. The most touch-bonded teams were the Boston Celtics and the Los Angeles Lakers, currently two of the league’s top teams; at the bottom were the mediocre Sacramento Kings and Charlotte Bobcats.
The same was true, more or less, for players. The touchiest player was Kevin Garnett, the Celtics’ star big man, followed by star forwards Chris Bosh of the Toronto Raptors and Carlos Boozer of the Utah Jazz. “Within 600 milliseconds of shooting a free throw, Garnett has reached out and touched four guys,” Dr. Keltner said.
To correct for the possibility that the better teams touch more often simply because they are winning, the researchers rated performance based not on points or victories but on a sophisticated measure of how efficiently players and teams managed the ball — their ratio of assists to giveaways, for example. And even after the high expectations surrounding the more talented teams were taken into account, the correlation persisted. Players who made contact with teammates most consistently and longest tended to rate highest on measures of performance, and the teams with those players seemed to get the most out of their talent.
The study fell short of showing that touch caused the better performance, Dr. Kraus acknowledged. “We still have to test this in a controlled lab environment,” he said.
If a high five or an equivalent can in fact enhance performance, on the field or in the office, that may be because it reduces stress. A warm touch seems to set off the release of oxytocin, a hormone that helps create a sensation of trust, and to reduce levels of the stress hormone cortisol.
In the brain, prefrontal areas, which help regulate emotion, can relax, freeing them for another of their primary purposes: problem solving. In effect, the body interprets a supportive touch as “I’ll share the load.”
“We think that humans build relationships precisely for this reason, to distribute problem solving across brains,” said James A. Coan, a a psychologist at the University of Virginia. “We are wired to literally share the processing load, and this is the signal we’re getting when we receive support through touch.”
The same is certainly true of partnerships, and especially the romantic kind, psychologists say. In a recent experiment, researchers led by Christopher Oveis of Harvard conducted five-minute interviews with 69 couples, prompting each pair to discuss difficult periods in their relationship.
The investigators scored the frequency and length of touching that each couple, seated side by side, engaged in. In an interview, Dr. Oveis said that the results were preliminary.
“But it looks so far like the couples who touch more are reporting more satisfaction in the relationship,” he said.
Again, it’s not clear which came first, the touching or the satisfaction. But in romantic relationships, one has been known to lead to the other. Or at least, so the anecdotal evidence suggests.
By JOHN TIERNEY, The New York Times, February 23, 2010
Suppose, as some experts advise, that the new national dietary guidelines due this spring will lower the recommended level of salt. Suppose further that public health officials in New York and Washington succeed in forcing food companies to use less salt. What would be the effect?
A) More than 44,000 deaths would be prevented annually (as estimated recently in The New England Journal of Medicine).
B) About 150,000 deaths per year would be prevented annually (as estimated by the New York City Department of Health and Mental Hygiene).
C) Hundreds of millions of people would be subjected to an experiment with unpredictable and possibly adverse effects (as argued recently in The Journal of the American Medical Association).
D) Not much one way or the other.
E) Americans would get even fatter than they are today.
Don’t worry, there’s no wrong answer, at least not yet. That’s the beauty of the salt debate: there’s so little reliable evidence that you can imagine just about any outcome. For all the talk about the growing menace of sodium in packaged foods, experts aren’t even sure that Americans today are eating more salt than they used to.
When you don’t know past trends, predicting the future is a wide-open game.
My personal favorite prediction is E, the further fattening of America, but I’m just guided by a personal rule: Never bet against the expansion of Americans’ waistlines, especially not when public health experts get involved.
The harder the experts try to save Americans, the fatter we get. We followed their admirable advice to quit smoking, and by some estimates we gained 15 pounds apiece afterward. The extra weight was certainly a worthwhile trade-off for longer life and better health, but with success came a new challenge.
Officials responded by advising Americans to shun fat, which became the official villain of the national dietary guidelines during the 1980s and 1990s. The anti-fat campaign definitely made an impact on the marketing of food, but as we gobbled up all the new low-fat products, we kept getting fatter. Eventually, in 2000, the experts revised the dietary guidelines and conceded that their anti-fat advice may have contributed to diabetes and obesity by unintentionally encouraging Americans to eat more calories.
That fiasco hasn’t dampened the reformers’ enthusiasm, to judge from the growing campaign to impose salt restrictions. Pointing to evidence that a salt-restricted diet causes some people’s blood pressure to drop, the reformers extrapolate that tens of thousands of lives would be saved if there were less salt in everybody’s food.
But is it even possible to get the public to permanently reduce salt consumption? Researchers have had a hard enough time getting people to cut back during short-term supervised experiments.
The salt reformers say change is possible if the food industry cuts back on all the hidden salt in its products. They want the United States to emulate Britain, where there has been an intensive campaign to pressure industry as well as consumers to use less salt. As a result, British authorities say, from 2000 to 2008 there was about a 10 percent reduction in daily salt consumption, which was measured by surveys that analyzed the amount of salt excreted in urine collected over 24 hours.
But the British report was challenged in a recent article in The Clinical Journal of the American Society of Nephrology by researchers at the University of California, Davis, and Washington University in St. Louis. The team, led by Dr. David A. McCarron, a nephrologist at Davis, criticized the British authorities for singling out surveys in 2008 and 2000 while ignoring nearly a dozen similar surveys conducted in the past two decades.
When all the surveys in Britain are considered, there has been no consistent downward trend in salt consumption in recent years, said Dr. McCarron, who has been a longtime critic of the salt reformers. (For more on him and his foes, go to nytimes.com/tierneylab.) He said that the most notable feature of the data is how little variation there has been in salt consumption in Britain — and just about everywhere else, too.
Dr. McCarron and his colleagues analyzed surveys from 33 countries around the world and reported that, despite wide differences in diet and culture, people generally consumed about the same amount of salt. There were a few exceptions, like tribes isolated in the Amazon and Africa, but the vast majority of people ate more salt than recommended in the current American dietary guidelines.
The results were so similar in so many places that Dr. McCarron hypothesized that networks in the brain regulate sodium appetite so that people consume a set daily level of salt. If so, that might help explain one apparent paradox related to reports that Americans are consuming more daily calories than they used to. Extra food would be expected to come with additional salt, yet there has not been a clear upward trend in daily salt consumption evident over the years in urinalysis studies, which are considered the best gauge because they directly measure salt levels instead of relying on estimates based on people’s recollections of what they ate. Why no extra salt? One prominent advocate of salt reduction, Dr. Lawrence Appel of Johns Hopkins University, said that inconsistent techniques in conducting the urinalysis surveys may be masking a real upward trend in salt consumption.
But Dr. McCarron called the measurements reliable and said they could be explained by the set-point theory:
As Americans ate more calories, they could have eased up on some of the saltier choices so that their overall sodium consumption remained constant. By that same logic, he speculated, if future policies reduce the average amount of salt in food, people might compensate by seeking out saltier foods — or by simply eating still more of everything.
The salt reformers dismiss these speculations, arguing that with the right help, people can maintain low-salt diets without gaining weight or suffering other problems. But even if people could be induced to eat less salt, would they end up better off? The estimates about all the lives to be saved are just extrapolations based on the presumed benefits of lower blood pressure.
If you track how many strokes and heart attacks are suffered by people on low-salt diets, the results aren’t nearly as neat or encouraging, as noted recently in JAMA by Michael H. Alderman, a hypertension expert at Albert Einstein College of Medicine. A low-salt diet was associated with better clinical outcomes in only 5 of the 11 studies he considered; in the rest, the people on the low-salt diet fared either the same or worse.
“When you reduce salt,” Dr. Alderman said, “you reduce blood pressure, but there can also be other adverse and unintended consequences. As more data have accumulated, it’s less and less supportive of the case for salt reduction, but the advocates seem more determined than ever to change policy.”
Before changing public policy, Dr. Alderman and Dr. McCarron suggest trying something new: a rigorous test of the low-salt diet in a randomized clinical trial. That proposal is rejected by the salt reformers as too time-consuming and expensive. But when you contemplate the potential costs of another public health debacle like the anti-fat campaign, a clinical trial can start to look cheap.
Observatory: Puzzle Solved: How a Fatherless Lizard Species Maintains Its Genetic Diversity
By SINDYA N. BHANOO, The New York Times, February 23, 2010
More than 40 years ago, Bill Neaves, then a young Ph.D. student, discovered how an all-female, asexual species of the whiptail lizard came to be. He found that the lizard was a cross between the female species of one type of lizard and the male species of another.
But what has puzzled him for years is how this all-female species maintains its high level of genetic variation, a contribution to evolutionary fitness that typically comes from sexual reproduction.
Despite reproducing without a male partner, this lizard species has a strong presence in the wild. Now, Aracely Lutes, a graduate student at the Stowers Institute for Medical Research in Kansas City, Mo., where Dr. Neaves works, has figured out the missing piece of the puzzle. The findings were reported Sunday in the journal Nature.
In a sexually reproducing lizard species, each lizard has 23 chromosomes from its mother, and 23 from its father.
During reproduction in the all-female species, Ms. Lutes found, all 46 of the mother’s chromosomes are duplicated, resulting in 92 chromosomes in each egg cell.
Those chromosomes then pair with their identical duplicates, and after two cell divisions, a mature egg with 46 chromosomes is produced. Since crossing-over during the cell divisions occurs only between pairs of identical chromosomes, the lizard that develops from the unfertilized egg is identical to its mother.
Importantly, each new lizard is also a replication of the original. Since the original was genetically diverse, pulling its chromosomes from two different species, its carbon copy descendants are, too.
It is because of this that the species has thrived over the generations. But unlike sexually reproducing species, these lizards will probably never evolve into a stronger species, Dr. Neaves said.
They “may be really well suited for the desert Southwest,” he said, “but when the next ice age comes, it may be that all of them get wiped out.”
Observatory: Crickets Warn Young Before Birth of Dangers of Wolf Spiders
By SINDYA N. BHANOO, The New York Times, February 23, 2010
If an expectant mother knew that dangerous creatures lurked around her, and knew also that she wouldn’t be around to take care of her young, she might be stressed.
And if she had a way to warn her young before they were born, surely she would.
Human mothers cannot do this, to the best of our knowledge. But pregnant crickets, it appears, do have the ability to forewarn. This is especially useful since crickets abandon their young after birth.
Researchers from the University of South Carolina Upstate and Indiana State University placed pregnant crickets in an enclosure where they were stalked, but not eaten, by a wolf spider, whose fangs had been coated with wax to protect the crickets.
The young of the spider-exposed mothers turned out to be more predator-savvy than those with mothers who were not exposed to the wolf spider; they stayed hidden longer, and were more likely to freeze when they encountered spider feces or spider silk.
In a second experiment, the researchers placed the juvenile crickets in an arena with a starving wolf spider with fully functioning fangs. Eventually, the spider got all the crickets, but the young born from spider-exposed mothers lasted longer in the arena of death.
The research was published last month in The American Naturalist.
What remains unclear is exactly how the crickets are warning their unborn. “We don’t know a specific mechanism,” said Jonathan Storm, a professor at the University of South Carolina Upstate in Spartanburg and one of the authors of the paper.
Although it is conjecture at this point, he said, “It’s possible that there could be some sort of hormone transmitted.”
Mind: Evidence That Little Touches Do Mean So Much
By BENEDICT CAREY, The New York Times, February 23, 2010
Psychologists have long studied the grunts and winks of nonverbal communication, the vocal tones and facial expressions that carry emotion. A warm tone of voice, a hostile stare — both have the same meaning in Terre Haute or Timbuktu, and are among dozens of signals that form a universal human vocabulary.
But in recent years some researchers have begun to focus on a different, often more subtle kind of wordless communication: physical contact. Momentary touches, they say — whether an exuberant high five, a warm hand on the shoulder, or a creepy touch to the arm — can communicate an even wider range of emotion than gestures or expressions, and sometimes do so more quickly and accurately than words.
“It is the first language we learn,” said Dacher Keltner, a professor of psychology at the University of California, Berkeley, and the author of “Born to Be Good: The Science of a Meaningful Life” (Norton, 2009), and remains, he said, “our richest means of emotional expression” throughout life.
The evidence that such messages can lead to clear, almost immediate changes in how people think and behave is accumulating fast. Students who received a supportive touch on the back or arm from a teacher were nearly twice as likely to volunteer in class as those who did not, studies have found. A sympathetic touch from a doctor leaves people with the impression that the visit lasted twice as long, compared with estimates from people who were untouched. Research by Tiffany Field of the Touch Research Institute in Miami has found that a massage from a loved one can not only ease pain but also soothe depression and strengthen a relationship.
In a series of experiments led by Matthew Hertenstein, a psychologist at DePauw University in Indiana, volunteers tried to communicate a list of emotions by touching a blindfolded stranger. The participants were able to communicate eight distinct emotions, from gratitude to disgust to love, some with about 70 percent accuracy.
“We used to think that touch only served to intensify communicated emotions,” Dr. Hertenstein said. Now it turns out to be “a much more differentiated signaling system than we had imagined.”
To see whether a rich vocabulary of supportive touch is in fact related to performance, scientists at Berkeley recently analyzed interactions in one of the most physically expressive arenas on earth: professional basketball. Michael W. Kraus led a research team that coded every bump, hug and high five in a single game played by each team in the National Basketball Association early last season.
In a paper due out this year in the journal Emotion, Mr. Kraus and his co-authors, Cassy Huang and Dr. Keltner, report that with a few exceptions, good teams tended to be touchier than bad ones. The most touch-bonded teams were the Boston Celtics and the Los Angeles Lakers, currently two of the league’s top teams; at the bottom were the mediocre Sacramento Kings and Charlotte Bobcats.
The same was true, more or less, for players. The touchiest player was Kevin Garnett, the Celtics’ star big man, followed by star forwards Chris Bosh of the Toronto Raptors and Carlos Boozer of the Utah Jazz. “Within 600 milliseconds of shooting a free throw, Garnett has reached out and touched four guys,” Dr. Keltner said.
To correct for the possibility that the better teams touch more often simply because they are winning, the researchers rated performance based not on points or victories but on a sophisticated measure of how efficiently players and teams managed the ball — their ratio of assists to giveaways, for example. And even after the high expectations surrounding the more talented teams were taken into account, the correlation persisted. Players who made contact with teammates most consistently and longest tended to rate highest on measures of performance, and the teams with those players seemed to get the most out of their talent.
The study fell short of showing that touch caused the better performance, Dr. Kraus acknowledged. “We still have to test this in a controlled lab environment,” he said.
If a high five or an equivalent can in fact enhance performance, on the field or in the office, that may be because it reduces stress. A warm touch seems to set off the release of oxytocin, a hormone that helps create a sensation of trust, and to reduce levels of the stress hormone cortisol.
In the brain, prefrontal areas, which help regulate emotion, can relax, freeing them for another of their primary purposes: problem solving. In effect, the body interprets a supportive touch as “I’ll share the load.”
“We think that humans build relationships precisely for this reason, to distribute problem solving across brains,” said James A. Coan, a a psychologist at the University of Virginia. “We are wired to literally share the processing load, and this is the signal we’re getting when we receive support through touch.”
The same is certainly true of partnerships, and especially the romantic kind, psychologists say. In a recent experiment, researchers led by Christopher Oveis of Harvard conducted five-minute interviews with 69 couples, prompting each pair to discuss difficult periods in their relationship.
The investigators scored the frequency and length of touching that each couple, seated side by side, engaged in. In an interview, Dr. Oveis said that the results were preliminary.
“But it looks so far like the couples who touch more are reporting more satisfaction in the relationship,” he said.
Again, it’s not clear which came first, the touching or the satisfaction. But in romantic relationships, one has been known to lead to the other. Or at least, so the anecdotal evidence suggests.
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