Hand to brain...

after about 10 weeks in the mother's womb, the human foetus already shows a distinct left- or right-handedness, say scientists from Northern Ireland. They say their finding could mean that contrary to the conventional idea that the brain dictates 'handedness', the reverse may be true: handedness may direct the way our brain develops.

Glenda McCartney and Peter Hepper at Queen's University, Belfast, used ultrasound to 'watch' the earliest hand movements of over 87 10-week-old foetuses to see which hand they moved most. It turned out that about 85 per cent of the foetuses were right-handed -- just as in the adult population ( New Scientist , Vol 158, No 2128).

To check whether this pattern changed later, the duo further scanned 17 foetuses at three-week intervals. This confirmed that once the hand preferences are established, they stick. The arm movements occur so early in the foetal development that the brain has not begun to control these, Hepper observes. Instead, the flailing hands are probably just a result of reflexes, he says. "There is no possible role for the brain at this early a stage," he notes.

The results may stand the conventional theory on it head. "What we are suggesting is that perhaps differential arm movement leads to differential brain growth," says Hepper. "Movements cause brain speciality, and not the other way around," he argues.

However, Marion Annett, a developmental psychologist at the University of Leicester, uk , is not convinced. "I think it is a very interesting finding. But I do not think it necessarily follows that the hand influences the brain," she points out.

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