Differential finger movements and hand preference.

In an attempt to replicate a study by Kimura and Vanderwolf (1970), normal left-handed and right-handed subjects were asked to flex a single finger or pairs of fingers at the middle joint. Both hands were found to be equally proficient at this task and no differences between right- and left-handers were found. When left-handers were divided into inverters and non-inverters according to hand-writing posture, a left hand superiority was a found for the right-handed and the left-inverted subjects, while the left-non-inverters showed a right hand superiority. Paired finger flexion was found to be more useful in discriminating between the handedness groups. These findings support the idea that the neural mechanism for hand preference is not based on an asymmetry in the control of fine movement. They also support the theory that two separate groups of left-handers exist, and the they can be differentiated by their handwriting postures.