What it means for something to be a bad experience for an individual is for it to make the individual feel bad. Negative feelings define bad life experiences, whereas positive feelings define good ones.
It could be argued that whether a moment is positive or negative for a person does not depend solely on that person's physiological experience of it. Indeed, disagreeing with our thesis may well require such an argument. But what else could make it positive or negative?
This passage neglects the fact that there are two different things we might mean in talking of 'bad life experiences'. We might mean to talk of subjectively unpleasant experiences, as the authors do. (But then their claims are tautological, when surely they had hoped to establish a substantive conclusion.) Alternatively, we might mean to talk of a life experience (or event) that was bad for you, i.e. undesirable for your sake. For a possible example of the latter, consider the experience of being subtly mocked (without realizing it). Though the undesirable feature of this circumstance is not subjectively transparent to you, nonetheless you (and others who care about you) generally have reason to hope that no such event actually befall you -- or so one might plausibly claim. This is the substantive question of welfare, which the authors fail to address or - it seems - even recognize.
In Solum's follow-up post, the authors set out their core argument as follows:
each of us has a veil of experience, and anything that happens outside that veil of experience and never affects it (even indirectly) has no effect on our lives.
Here they appear to confuse the metaphysical question whether an event "affects" you, in the sense of altering your intrinsic properties, with the normative question of welfare: whether it "affects" you in the sense of being an event that you have self-interested reasons to care about. (In fairness, I think even Shelly Kagan may have once made a similar mistake.) These are wildly different questions, and if one thinks that they are linked in any way, this would require substantial argument. It is far from obvious that welfare supervenes on our intrinsic properties. (Presumably only hedonists will believe this.) Sometimes people talk of one's "life" or "life story" in a broader sense that includes all of the external events and relations that could conceivably be relevant to assessing one's life along any dimension (one's success, popularity, and - of course - welfare). It would then follow trivially that one's welfare supervenes on the intrinsic properties of one's "life" in this broad sense. But this is compatible with any of the main theories of welfare, since one's "life" in this broad sense includes all manner of external events and relations.
I was also struck by the authors' self-defeating arguments against objectivism. Consider the following:
According to the objectivist view, not only don't the individuals know what's good for them, but their view of what's good for themselves doesn't determine what's good for them--no matter how considered or accurate (in terms of happiness) a view it is.
But the authors' own view is no different in this regard. They are hedonists, not preferentists. Even if I care about truth more than happiness, the authors will paternalistically insist that happiness is in fact what's good for me. For them, individuals' own views of "what's good for themselves" are strictly irrelevant -- no matter how "considered" and well-informed our self-regarding preferences might be. (Of course, even preferentists think that people might have false beliefs about welfare: some people believe the competing theories, after all! But there's no avoiding that.)
Their main objection to preferentism is that people may have preferences about distant events that are intuitively irrelevant to their welfare. (They mention 'Sheila the environmentalist', who passively hopes that a rare foreign squirrel avoids extinction.) But this merely shows that preferentists need to restrict which desires count in determining one's welfare, say to those that concern one's own "life story". One might wish to critically examine whether various such proposed restrictions are sufficiently well-defined and non-circular to do the job. But the only such view that the authors consider is the explicitly circular view according to which only "self-interested" preferences count for determining your self-interest. They then respond:
A self-interested, restricted theory of welfare demands that the individual actually receive some benefit before one can say that her welfare has increased; this conception of "benefit" is rendered meaningless unless the individual actually experiences the benefit. To claim otherwise--to argue that an individual's welfare can improve without that improvement registering subjectively--is to welcome Sheila and her Sri Lankan squirrel back into the fold.
But this is effectively just to assert that no independent restriction can be found. There's no argument here, and they appear completely oblivious to the fact that philosophers like Derek Parfit (with his "success theory") have actually proposed some prima facie plausible candidates for this role -- proposals that they're really obliged to engage with. It's extremely frustrating.
[Compare 'psychologists mangling philosophy'. As a general rule, if you're going to attempt scholarly work that's beyond your disciplinary expertise, it would seem wise to consult with a colleague from the relevant discipline, so that they might flag these sorts of problems.]