TOLEDO, Ohio, Oct 21, 2001 (United Press International via COMTEX) — Researchers say when it comes to remembering vivid details of an event, left-handed people are more likely than right-handed people to have such memories.
Researchers suspect such detailed memories — not just recollection of facts but the events associated with them — are more likely to be created in people with strong connections between the two halves of the brain. People who are left-handed, and their immediate relatives, tend to have more connections between the different hemispheres of the brain than do people who are right-handed.
“I don’t think our results suggest in a global way that either lefties or righties have an advantage over the other in terms of remembering facts … but it suggests that left-handers might have richer memories than righties,” said Stephen D. Christman, a professor of psychology at the University of Toledo in Ohio.
Because only 10 percent of people are left-handed, it is difficult to study large numbers of them. So Christman and his colleague, Ruth E. Propper, looked at right-handed people who either had or did not have immediate relatives who were left-handed. Since handedness has a genetic component, right-handed family members of lefties also tend to have a thicker bundle of fibers connecting the two halves of the brain than do other righties.
In the first experiment, the psychologists studied 180 Air Force recruits, showing them lists of 55 words to study. In subsequent tests, those recruits who had immediate family members who were left-handed were better than those who did not when it came to listing words they recalled from the study session.
Right-handed people with only right-handed family members, in contrast, were better at completing word fragments than were the lefty relatives.
In a second experiment, the two researchers tested 84 right-handed undergraduate students by presenting words or letter strings in series. On a computer screen, objects displayed to the left of center will activate the right brain; the left-brain registers words or letters shown to the right of center. The researchers were trying to determine if event recall was associated with using both hemispheres of the brain.
Students were faster at remembering whether they had seen a word or letter string earlier in the test when the stimulus was initially presented on one side and repeated on the other. In contrast, students were better at recognizing whether a given item was a word or a random string of letters when the word or letter string was shown on the same side the second time.
The left-brain seems to remember facts, while the right brain adds in color and context, Christman said. “A single hemisphere can do it (remember an event) but not as quickly or as accurately as when you have both hemispheres working together,” he said.
This research “ties variation in an aspect of memory to a biological aspect of the human brain,” said Sandra Witelson, the Albert Einstein/Irving Zucker professor of neuroscience at McMaster University in Hamilton, Ontario. “We’ve always known there are variations in memory between people … this study shows that (one kind of) memory is associated with handedness, and handedness itself is known to be associated with brain structure.”
“These memory differences are interesting,” said Dahlia Zaidel, adjunct professor of psychology and behavioral neuroscience at the University of California, Los Angeles. Still, she cautions that while some studies have found that lefties have better connections between the two halves of the brain, other studies have shown no differences.
Christman’s findings are especially interesting because memories about events are crucial for the development of a person’s self-identity and understanding of who they are, Witelson said.
The findings that connections between brain hemispheres interact with how people remember events might help explain a long-standing question, Christman said. Most people cannot remember events from their earliest childhood. Vivid memories seem to form around the age of 4 or 5 at the earliest.
The reason recollections of events do not form earlier, Christman pointed out, is the bundle of fibers connecting the two halves of the brain does not mature until around 4 or 5. The two events might be linked, he suggested.
He said he is exploring whether lefties, who generally have more connections between the two parts of the brain, can recall earlier memories than can righties. He and colleagues also are exploring whether a simple technique to temporarily boost nerve signals between the brain hemispheres can boost memory. Wiggling the eyes back and forth for 30 seconds activates both brain hemispheres, he said. Though so far it as an untested hypothesis, he plans to study whether such rapid eye movements might help people remember simple things like, for example, where they parked their car.