Question 2: Doubtless some of the behaviors I listed have completely different explanations, some of which might not involve masochism at all. Which do you think involve enjoying pain? Can you cluster them by causal mechanism?
None of the examples necessarily involve the enjoyment of pain so they don’t necessarily fit the technical meaning of masochism. They do fit the colloquial definition of masochism though, which is somewhat different. More along the lines of ‘enjoying doing things that make you feel like a tough badass even though pain may be an undesired side effect’. I do that kind of thing (and most of your list) rather enthusiastically but don’t enjoy pain itself much at all. Sure, if running marathons didn’t hurt they would lose some of their appeal—but only indirectly and because it’d mean anyone could be doing them.
None of the examples necessarily involve the enjoyment of pain so they don’t necessarily fit the technical meaning of masochism. They do fit the colloquial definition of masochism though, which is somewhat different. More along the lines of ‘enjoying doing things that make you feel like a tough badass even though pain may be an undesired side effect’. I do that kind of thing (and most of your list) rather enthusiastically but don’t enjoy pain itself much at all. Sure, if running marathons didn’t hurt they would lose some of their appeal—but only indirectly and because it’d mean anyone could be doing them.