New report challenges notion that left-handers die prematurely

April 05, 1993|By Los Angeles Times

LOS ANGELES -- A University of California at Los Angeles study due next month is likely to help settle the long-simmering dispute over whether left-handed people die earlier than their right-handed counterparts.

Contrary to the highly publicized claims that a statistical shortage of elderly left-handers in the population means that left-handers do die earlier, the UCLA study suggests that there is no significant difference in the death rates of the two groups. The researchers found that many older persons classified as right-handers were born lefties whose parents and teachers forced them to convert.

The issue reached new levels of contention two years ago when psychologists Stanley Coren of the University of British Columbia and Diane Halpern of California State University at San Bernardino reported that left-handers in California's San Bernardino and Riverside counties die an average of eight years prematurely. Their report was met with a hail of criticism and was followed closely by a flurry of scientific publications both supporting and rebutting their findings.

None of that evidence has swayed believers on either side of the issue, but the new report may have more credibility because it directly addresses the issue that is at the nub of the controversy:

Why are there so few left-handers among the elderly in the population?

Mr. Coren, Ms. Halpern and others argue that some left-handers are more susceptible to disease and that all left-handers are susceptible to the risks of using tools, cars and other implements of a modern society designed for right-handers.

The bulk of scientists, however, have long argued that this apparent lack of old left-handers simply reflects social pressures earlier in this century that caused parents and teachers to force left-handed children to write and eat with their right hands. But there was no proof for this contention -- until now.

UCLA psychologist Paul Satz and his colleagues at UCLA and the University of Bergen in Norway took what Mr. Satz termed the "rather simple-minded" approach of asking 2,787 people not only which hand they use for a variety of tasks, but also whether they had been made to switch hands as a child.

Their results, to be reported in the May issue of the journal Neuropsychologia, show that many people, particularly those who are now over 60, say they were indeed forced to switch as children and that this increased proportion in the older groups largely offsets the decline in incidence of left-handers.

"The left-handers are still present in older populations," Mr. Satz concluded. "They simply show up on most surveys as right-handers."

Mr. Coren, shown the UCLA report, argues that hand-switching does not account for all the loss of left-handers with increasing age. Mr. Satz's figures still show a small trend toward fewer left-handers in the older populations, but it now seems clear, other experts said, that the risk to left-handers is substantially smaller than Mr. Coren and Ms. Halpern have argued.

In the population at large, about 9 percent of women and 13 percent of men are left-handed, but many studies have shown a peculiar age distribution. At the age of 10, 15 percent of the population is left-handed. At 20, 13 percent. By age 50, the proportion drops to 5 percent, and beyond age 80, it is less than 1 percent.

Scientists are not sure why left-handedness develops. Genetics may cause up to half the cases.

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