Task-dependent "reversed" handedness: why use left hand for some tasks? How is it controlled by the brain?

Question

I am right-handed. Which means that when I hammer down a nail, I hold the nail in my left hand, with which I can hold it straight and at a controlled position.

This is true in situations where the task of holding something in place is simultaneous with a more complex task, such has hammering, done with the right hand. But I note that even when there is no other task, I personally use my left hand to hold in place, e.g., a bottle that I am filling up in a stream of water.

To generalize a little, it seems to me that while I use my right hand for precise motion or applying a force, I'll use my left hand to maintain a position against forces.

Is this behaviour something documented? Does one develop specific brain control to implement this controlled-position tasks?

Answer 1

The dynamic-dominance hypothesis of handedness states that the essential factor that distinguishes dominant from nondominant arm performance is the facility governing the control of limb dynamics. Sainburg (1) writes that

It should be noted that dominant arm advantages do not apply to all tasks, or all aspects of tasks. Healey et al. (1986) examined an extensive range of tasks and found that four factors or groups of tasks accounted for 80% of the variance in hand preference among the 110 subjects tested. Tasks that were almost exclusively associated with dominant arm use included activities requiring precision in interjoint coordination and trajectory formation. (...) In contrast, tasks that involved spatially orienting a body segment posture were more often performed with the nondominant arm. These tasks included posturing the hand to point toward a distant object, which is similar to other functional tasks such as holding a piece of paper that is being cut with scissors, or orienting the hand in space for catching a baseball. Such postural orientation tasks are less dependent on intersegmental dynamics, since the trajectory used to attain the posture is not critical for task success. The dynamic dominance hypothesis thus appears to account for the extent to which hand preferences for specific activities are lateralized.

This appears to be consistent with your experience.