Hand preference decided at 10 weeks

LONDON (Reuters) - Whether a person will be right-handed or left-handed could be decided early in the womb when the foetus is about 10 weeks old.


Scientists who studied ultrasound scans of 1,000 foetuses and followed the progress of some of them after birth, found that if a foetus preferred to suck its right thumb more than its left at 10 to 12 weeks old the child tended to be right-handed.


"The hand you favour as a 10-week-old foetus is the hand you will favour for the rest of your life," New Scientist magazine said on Wednesday.


The findings, by Peter Hepper and researchers at Queen's University in Belfast, Northern Ireland challenge current thinking that hand preference does not develop until a child is 3 or 4 years old.


The scientists also looked at hand movement in the womb which begins at about 10 weeks and found a similar association between preference and handedness after birth.


Hepper said there is no evidence that the brain has any control over the early movements in the womb and suggests it is more likely to be a local reflex arc of the spinal cord.


"He speculates that the foetus may have a preference for one side of its body simply because that side develops slightly faster," the magazine added.