填空题

Sinister Minds: Are Left-Handed People Smarter
A. In 1903, Cesare Lombroso, the father of modern criminology (犯罪学), summarized his views on the left-handed of the world. "What is sure," he wrote, "is that criminals are more often left-handed than honest men, and lunatics are more sensitively left-sided than either of the other two." Left-handers were more than three times as common in criminal populations as they were in everyday life, he found.
B. The prevalence among cheaters was even higher: up to thirty-three percent were left-handed—in contrast to the four percent Lombroso found within the normal population. He ended with a soft tone. "I do not dream at all of saying that all left-handed people are wicked, but that left-handedness, united to many other traits, may contribute to form one of the worst characters among the human species."
C. Though Lombroso’s science may seem suspect to a modern eye, less-than-favorable views of the left-handed have persisted. In 1977, the psychologist Theodore Blau argued that left-handed children were over-represented among the academically and behaviorally challenged, and were more vulnerable to mental diseases. "Sinister children," he called them. The psychologist Stanley Coren, throughout the eighties and nineties, presented evidence that the left-handed lived shorter, more impoverished lives, and that they were more likely to experience delays in mental and physical maturity, among other signs of "neurological insult or physical malfunctioning."
D. But over the past two decades, the data that seemed compelling have largely been challenged. In 1993, the psychologist Marian Annett, who has spent half a century researching "handedness," as it is known, suspected the basic foundation of Coren’s findings. The data, she argued, were fundamentally flawed: it wasn’t the case that left-handers led shorter lives. Rather, the older you were, the more likely it was that you had been forced to use your right hand as a young child.
E. The mental-health data have also been questioned: a 2010 analysis of close to fifteen hundred individuals that included the mentally ill and their non-affected siblings found that being left-handed neither increased the risk of developing mental disease nor predicted any other cognitive or neural disadvantage. And when a group of neurologists scanned the brains of four hundred and sixty-five adults, they found no effect of handedness on either grey or white matter volume or concentration, either globally or regionally.
F. Left-handers may, in fact, even derive certain cognitive benefits from their preference. This spring, a group of psychiatrists from the University of Athens invited a hundred university students and graduates—half left-handed and half right—to complete two tests of cognitive ability. In the Trail Making Test, participants had to find a path through a batch of circles as quickly as possible. In the hard version of the test, the circles contain numbers and letters, and participants must move in ascending order while alternating between the two as fast as possible.
G. In the second test, Letter-Number Sequencing, participants hear a group of numbers and letters and must then repeat the whole group, but with numbers in ascending order and letters organized alphabetically. Lefties performed better on both the complex version of the T.M.T.—demonstrating faster and more accurate spatial skills, along with strong executive control and mental flexibility—and on the L.N.S., demonstrating enhanced working memory. And the more intensely they preferred their left hand for tasks, the stronger the effect.
H. The Athens study points to a specific kind of cognitive benefit, since both the T.M.T. and the L.N.S. are thought to engage, to a large extent, the right hemisphere of the brain. But a growing body of research suggests another, broader benefit: a boost in a specific kind of creativity—namely, divergent thinking, or the ability to generate new ideas from a single principle quickly and effectively.
I. In one demonstration, researchers found that the more marked the left-handed preference in a group of males, the better they were at tests of divergent thought. (The demonstration was led by the very Coren who had originally argued for the left-handers’ increased vulnerability to mental illness.) Left-handers were better, for instance, at combining two common objects in novel ways to form a third—for example, using a pole and a tin can to make a birdhouse. They also excelled at grouping lists of words into as many alternate categories as possible.
J. Another recent study has demonstrated an increased cognitive flexibility among the ambidextrous (双手灵巧的) and the left-handed—and lefties have been found to be over-represented among architects, musicians, and art and music students (as compared to those studying science).
K. Part of the explanation for this creative edge may lie in the greater connectivity of the left-handed brain. In a meta-analysis of forty-three studies, cognitive neuroscientists concluded that the bundle of fibers that connects the brain’s hemispheres was slightly but significantly larger in left-handers than in right-handers. In 1989, a group of Connecticut College psychologists suggested that the creativity boost was a result of the environment, since left-handers had to constantly improvise to deal with a world designed for right-handers.
L. In a 2013 review of research into handedness and cognition, a group of psychologists found that the main predictor of cognitive performance wasn’t whether an individual was left-handed or right-handed, but rather how strongly they preferred one hand over another. Strongly handed individuals, both right and left, were at a slight disadvantage compared to those who occupied the middle ground—both the ambidextrous and the left-handed who, through years of practice, had been forced to develop their non-dominant right hand. In those less clear-cut cases, the brain’s hemispheres interacted more and overall performance improved, indicating there is something to left-handed brains being pushed in a way that a right-handed one never is.
M. Whatever the ultimate explanation may be, the advantage appears to extend to other types of thinking, too. In a 1986 study of students who had scored in the top of their age group on either the math or the verbal sections of the S.A.T., the prevalence of left-handers among the high achievers—over fifteen percent, as compared to the roughly ten percent found in the general population—was higher than in any comparison groups, which included their siblings and parents.
N. Among those who had scored in the top in both the verbal and math sections, the percentage of left-handers jumped to nearly seventeen percent, for males, and twenty percent, for females. That advantage echoes an earlier sample of elementary-school children, which found increased left-handedness among children with I.Q. scores above a hundred and thirty-one.
O. Lombroso’s scientific conclusions about criminal physiology may be closer to phrenology (颅相学) than to any modern understanding of the brain. But he might not have been so far off the mark when he hypothesized that by looking at someone’s hands, we could learn something about the inner workings of their minds—though those workings have more to do with cognitive achievement than any inclination to commit highway robbery. Michelangelo and da Vinci were left-handed, after all. As were three of the last four occupants of the White House; the only right-handed President since the end of the Cold War has been George W. Bush.
The fact that left-handers have to try hard to handle a world designed for right-handers contributes to their creative edge.