Sherman James, an epidemiologist [someone who researches epidemic diseases] at the University of Michigan, describes a personality type named John Henryism. The name refers to the American folk hero who, hammering a six-foot-long steel drill, tried to out-race a steam drill tunneling through a mountain. John Henry beat the machine, only to fall dead from the superhuman effort.

As James defines it, John Henryism involves the belief that any and all demands can be vanquished, so long as you work hard enough. On questionnaires, John Henry individuals strongly agree with statements such as "When things don't go the way I want, it just makes me work even harder," or "Once I make up my mind to do something, I stay with it until the job is completely done." They believe that with enough effort and determination they can regulate all outcomes.