If so, what should we call the more general phenomenon of "deriving pleasure from one's own pain"

I don't know, but not "masochism." Whether these behaviors even hang together as a "general phenomenon" is an empirical question that is not yet answered. Let's look at some of Phil's examples:

• Listening to music turned up so loud that it hurts

Are people who do this actually enjoying the pain, or they merely tolerate it because they like loud music?

• Movies, especially horror movies
• Roller coasters

I once read that one of the main enjoyments in horror movies is not watching it, but the relief afterward; if true, this would be a difference from masochism. Another difference from masochism is that horror movies may be experienced as scary, while in masochism, sensations that would normally be painful are not necessarily experienced as painful.

However, a component that horror movies share with masochism and rollercoasters is arousal of the sympathetic nervous system (i.e. fight-or-flight). Whether horror movies also result in release of endorphins, like exercise and masochism, I don't know.

• Enjoying exercise

My guess is that in painful exercise, people aren't really deriving pleasure from their pain. Rather, pain is signifying that they are getting closer to their exercise goals, and is linked to feelings of accomplishment. People may derive pleasure from endorphins released during exercise, which would be a similarity with masochism. Furthermore, exercise may involve an altered state of mind, like masochism.

• Being Bruce

For this point, we do have a name: self-defeating behavior. There may be many motives for self-defeating behavior, such as insecurity, negative self-concept, or desire to be right about beliefs that limit oneself. Although these factors may coexist with masochism in some people, there is no reason to believe that the link is necessary or that they are part of masochism. There is also currently know evidence that self-defeating behavior is linked to certain factors in masochism, such as arousal of the sympathetic nervous system or release of endorphins.

As for masochism itself, it's misleading to describe it as "deriving pleasure from one's own pain." Sensations that non-masochists might experience as pain (or masochists themselves when not aroused), masochists might not experience as pain, but rather as pleasure or stimulation. In The Social Dimension of Sex, Roy Baumester suggests that masochism involves temporary escape from the self (which to me, is plausible as a factor in masochism, but not as a complete explanation). This would be a similarity with exercise, videogames, and perhaps horror movies. However, the particular self-escaping mental state would be different: the flow state) of exercise and videogames is not the same state as subspace. Escaping oneself is different from defeating oneself, which requires a self to defeat.

In Phil's supposedly masochistic pursuits, there are actually a bunch of completely different factors:

• Experiencing typically painful sensations as pleasure
• Experiencing pain, but as information about one's success
• Seeking pain or failure as confirmation of one's insecurities
• Escaping the self
• Enjoying sympathetic nervous system arousal
• Enjoying endorphins
• Enjoying the relief you feel after pain or discomfort
• Sexual pleasure

Something else to emphasize about masochism is the sexual element, particularly the link to sexual submission (though submissiveness and masochism are not the same thing). In my view, there is something fundamentally different about the psychology of masochists from typical "vanilla" people, and perhaps a biological difference also; that's why I like the description of BDSM interests as a different sexual orientation, or set of sexual orientations. It's problematic to take the psychology of this taxon of people, and generalize from it to the psychological traits of the general population.

Most of Phil's items, including sexual masochism, have some similarities with all other items, and fundamental differences from all the other items. Not all these phenomena are accurately described as deriving pleasure from one's pain, and they can't be fit into the term masochism; doing so will lead to more analytical confusion than clarity.

and, for sadism, "deriving pleasure from other people's pain")? The latter thing, especially, seems to me to be just about the worst thing in the world, and it would be a great tragedy if, out of an overzealous desire to avoid bigotry, we lost the ability to criticize and be emotionally resolved against it.

First, I should say that my objections to Phil's post are not on the grounds of bigotry. Second, I agree with you we should not lose our ability to criticize terrible things due to a politically correct avoidance of "labeling" and necessary categorizations.

Yet the need to morally condemn something shouldn't make us careless about how we categorize it. Like masochism, "sadism" is often used in a non-rigorous way. Enjoying giving someone pain in a safe, sane, and consensual context, is different from the behavior of sexually-motivated serial killers, who do not care about consent and have genuine impulse-control problems. And giving sexually-motivated pain is different from enjoying giving pain out of hatred, experimentation, or political motivations.

In my view, the word sadism should be reserved for when there is a sexual motivation. Otherwise, describing killers and mass-murderers as "sadistic" obscures the many non-sexual motivations behind killing. Although sexually-motivated serial killers are highly cognitively accessible due to the availability heuristic, the "worst thing in the world" (at least in the sense of the body count caused) is probably not sexually motivating killing, but rather political and ideological related killing.