Line bisection by left-handed preschoolers: a phenomenon of symmetrical neglect.

When a normal dextral attempts to bisect a horizontal line placed across his/her midline, there is a tendency for the transection to be placed slightly to the left of true center, a tendency which may be a little more pronounced when the left hand is used. However, left-handed children at or younger than 5 years of age err substantially to the left with the left hand and to the right with the right hand. This symmetrical neglect of extents contralateral to the hand currently in use, which may possibly reflect relatively greater commissural immaturity in left-handers, was not seen in dextral children of comparable ages, whose performance closely followed adult patterns.