Do right-handed people live longer?Expert answers to this and other questions from curious readers.
There’s always been something sinister about being left-handed. But shorter life spans? That’s downright creepy. The notion apparently sprang from a Canadian psychologist named Stanley Coren, who declared in his 1992 book, The Left-Handed Syndrome, that left-handers, on average, lived about a decade less than right-handers do.
For the previous decade, Coren and others who study “handedness” in the population (90 percent are right-handed, with twice as many lefties among men than women) had amassed data that seemed to show that as the population aged, the percentage of lefties kept decreasing.
What could be killing off the lefties so virulently? Lots of hypotheses arose. The dangers of operating machines and equipment designed for right handers. A developmental or pathological irregularity. A greater desire to take risks. Nobody knew.
Until 1993. In that year scientists at the National Institutes of Health and Harvard University co-authored a study published in the American Journal of Public Health. They examined the death reports of nearly 4,000 Bostonians over the age of 65. Critically, each report contained accurate information about hand dominance, gathered for a separate study. The result? Over six years, the death rate for righties was 32.2 percent, for lefties 33.8 percent, a statistically insignificant difference.
Dr. Marcel Salive, one of the co-authors, said he thought data from previous studies had been misinterpreted. “As a consequence of that interpretation,” he told The New York Times, “a lot of people had unwarranted fears.”
So take heart, lefties. Even though the misinformation persists, you weren’t handed a mortal curse at birth.
Is it true people use only 10 percent of their brains?
Among the most popular science myths, this one has been around for more than a century. Nobody knows how it got started, but it’s certainly been a useful motivational tool for generations of nagging parents (“Billy, just think what you could make of yourself if you tried using the other 90 percent!”), advertisers who hint that if we use their products we must be pretty smart cookies, and psychics who claim their powers come from the untapped portion.
Along the way, dozens of prominent scientists—including Albert Einstein, William James and Margaret Mead—have helped preserve the adage. While these folks were highly qualified in their fields, none was a neuroscientist.
“If it were the case that we used only 10 percent of our brain,” says Professor Reza Shadmehr, a neuroscientist at Johns Hopkins University School of Medicine, “then damage to a small part should have little impact on our abilities. We know from studies of stroke patients that when a small portion of the brain is damaged, there are often devastating consequences.”
“Even while you sleep, the brain is quite active, particularly during rapid eye movement [REM] sleep when dreaming occurs,” says Dr. Sterling Johnson, assistant professor of medicine at the University of Wisconsin School of Medicine and Public Health. “In this stage of sleep, the brain’s electrical activity is the same as in your normal wakeful state.”
Besides clinical observations, brain scans (both PET and MRI) also provide evidence that many places in the brain are active during a variety of tasks, according to Dr. Eric Chudler, a neuroscientist at the University of Washington in Seattle.
“It appears that there is no hidden storehouse of untapped brain power,” Chudler notes. “We use all of our brain.”
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