The left hemisphere encodes tool use. Its preference for this is so strong that even left-handed folks encode tool-use in the left hemisphere, which means that the round trip from hand to brain goes left hand -> right hemisphere (b/c each hemisphere controls the opposite side of the body) -> left hemisphere (tool circuits) -> right hemisphere -> left hand, which is waaay less efficient than right hand -> left hem -> right hand. (https://www.ted.com/talks/iain_mcgilchrist_the_divided_brain)

So, the left hand's failure to pantomime screwdriver use probably reflects the commissurotomy patient's right hemisphere's inability to access her left hemisphere's knowledge of tools. (That this only happens when eyes are closed probably means the right hemisphere just observed and copied the right hand's behavior when eyes were open.)

Had a fun chat with someone interested in this at a bar a few weeks ago who offered a theory that the best pro basketball players are right hand/right eye dominant or left hand/left eye dominant, and that anybody with mixed dominance just can't cut it. Apparently the military just wont take you as a pilot or sniper if you have mixed hand/eye dominance?

Calling it now: laterality is central to who we are, and is currently underappreciated—especially in AI research (though I'd be delighted to hear from AI folks who disagree!).

EDIT: lots