Mar. 8, 1999 By Victoria White
GAINESVILLE, Fla.---While much of the world is accustomed to driving in the right lane, in some ways the human brain might be better suited to left-side navigation, a new University of Florida study suggests.
“In our laboratory experiment, which did not involve driving, we found that the brain may pay more attention to faraway distractions when they are on the left than on the right, a visual attentional bias that causes people to be drawn toward the distraction,” said Dr. Anna Barrett, a visiting research assistant professor in the UF College of Medicine’s department of neurology.
“For U.S. drivers, ‘left far space’ is extremely important, because that is where we see oncoming traffic.”
Barrett worked on the experiment with Dr. Kenneth Heilman, the James E. Rooks Jr. professor of neurology, and Dr. Gregory Crucian, a visiting research assistant professor in neurology. Their work is one piece of a wider effort by scientists to understand how the brain processes and prioritizes information received through the senses. Such research holds wide-ranging implications for understanding how people learn and remember, respond to emergencies or even how they are attracted to commercial advertising.
Most drivers appear to have little trouble adjusting to this attentional bias, said Barrett, who presented her findings (2/11/99) in Boston at the annual U.S. meeting of the International Neuropsychological Society. But it may pose difficulties for those who have suffered a brain injury or who may be impaired neurologically-- by alcohol consumption, for example.
“Several years ago, we met a patient who had had a stroke who told us one of her major concerns was that she veered when she drove,” said Barrett, explaining the study’s origins. “She noticed that when there were people on the side of the road, she would steer toward them. She had problems with directing her movements in space when she could see a distraction ahead.”
Barrett’s work builds upon research conducted in Heilman’s laboratory. Heilman and his colleagues at UF’s Center for Neuropsychological Studies and the UF Brain Institute have demonstrated that the brain’s right hemisphere plays a dominant role in governing how people allocate attention.
“The way the brain is set up, images viewed on the left go directly to the right side of the brain for processing,” Heilman said. It stands to reason, then, that what is viewed on the left side would really grab your attention because it goes right to the hemisphere that is dominant for attentional functions.”
In an age when scientific research often requires expensive imaging systems or other high-technology devices, Barrett’s experiment is notable for the simplicity of its design. The equipment included a laser pointer and four lines of different lengths, which were shown repeatedly to nine research participants. Each participant viewed the lines at distances of 1 foot and 5.5 feet. Only right-handed people participated, because the brains of left- and right-handers can differ in how they distribute functions between the left and right hemispheres.
“We asked the participants to use the laser pointer to indicate the middle of the line segments,” Barrett said. “I stood quietly to either the left or the right of the line to see whether a stimulus that was irrelevant to their task--myself--affected their performance.”
Each participant performed 48 line bisections. They consistently misjudged the center by placing it farther to the left than it actually was.
“What was particularly interesting, however, was that in far space, their error to the left was influenced by where I stood,” Barrett said. “Subjects pointed about 3.5 inches farther leftward when I was standing on the left than when I stood on the right of the far line.”
The lines used at the far distance were about 48.5 and 53 inches long.
“If you’re driving 30 mph under optimum conditions, and something distracts you in far left space, 3 inches of steering error probably has little effect,” Barrett said. “But if you’re speeding at 80 mph, you have a neurological impairment, and something distracting comes into left far space, such as an oncoming car, you could be at greatly increased risk of accident because of this attentional bias."
International Neuropsychological Society: http://www.med.ohio-state.edu/ins/index.html
National Institute of Neurological Disorders: http://www.ninds.nih.gov
Recent UF Health Science Center news is available at http://www.health.ufl.edu/hscc/index.html
More information about the UF Brain Institute is found at http://www.ufbi.ufl.edu
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