Not only that, but medical doctors claim that the shift of the heart is of too little consequence to be a factor. Another theory for handedness is related to the last one mentioned. Most soldiers hold their shield with their left hand to protect their heart while engaged in battle, and thus use their right hand to hold their weapon. Those last few theories were ones that are rather obsolete. The next two theories that shall be presented are ones that are currently held as very possible and likely.
Many scientists believe that handedness is genetic.
This factor disposes it's carrier to be right-handed. She studied this theory by interviewing children whose parents were both left-handed. She studied the speed with which the children could perform a peg-sorting task. These results back up her prediction that the hand preference of those without the factor would be determined by chance. The human brain is divided into two hemispheres, the left and the right hemispheres.