Researchers in Auckland are studying twins to see whether a person's genes determine whether they will become left or right-handed.
They are particularly interested in identical twins, known as "mirror twins", because one is left-handed and the other is right-handed.
Auckland University psychology professor Mike Corballis has a Marsden Fund grant to examine whether "handedness" is linked to genetics and brain asymmetry.
He says almost a quarter of identical twins differ when it comes to which hand dominates.
Professor Corballis says he believes a particular gene may control right-handedness but if that gene is lacking, which hand a person will prefer becomes random.
He is recruiting pairs of twins, and others, for the three-year study, which will incorporate the use brain scans to study the brain structure and functioning of mirror twins.
