It’s less clear how we should model this case from the point of view of FDT, and there are a variety of options. The most natural and illustrative, we think, is to assume that what actions you would or would not perform in various (hypothetical or real) circumstances determines whether you’re a psychopath. What actions you would perform in which circumstances is in turn determined by your decision algorithm. On this reading of this case, the potential outputs of your decision algorithm affect both whether you’d press the button and whether you’re a psychopath. In practice, this leads the FDT agent always to refrain from pressing the button, but for very different reasons from the CDT agent. [The FDT agent] reasons that if she were to press the button that kills so many people, then she would be a psychopath. She does not regard her psychopathic tendencies—or lack thereof—as a fixed state of the world isolated from what decision she actually makes here. This seems like the right reasoning, at least on this understanding of what psychopathy is. Psychopaths just are people who tend to act (or would act) in certain kinds of ways in certain kinds of circumstances. We can take for granted that everyone is either born a psychopath or born a non-psychopath, and that [the FDT agent’s] action cannot causally change this condition she was born with. Yet if this condition consists in dispositions to behave in certain ways, then whether [the FDT agent] is a psychopath is subjunctively tied to the decisions she actually makes. If you would not perform A in circumstances C, then you also would not be the kind of person who performs actions like A in circumstances like C. FDT vindicates just this sort of reasoning, and refrains from pressing the button for the intuitively simple reason of “if I pressed it, I’d be a psychopath” (without any need for complex and laborious ratification procedures). When we intervene on the value of the FDT(P,G) variable, we change not just what you actually do, but also what kind of person you are.
From Cheating Death in Damascus (bold emphasis mine):