Suppose someone — who, for reasons that will become apparent, Quinn calls the self-torturer — has a special electric device attached to him. The device has 1001 settings: 0, 1, 2, 3, …, 1000 and works as follows: moving up a setting raises, by a tiny increment, the amount of electric current applied to the self-torturer's body. The increments in current are so small that the self-torturer cannot tell the difference between adjacent settings. He can, however, tell the difference between settings that are far apart. And, in fact, there are settings at which the self-torturer would experience excruciating pain. Once a week, the self-torturer can compare all the different settings. He must then go back to the setting he was at and decide if he wants to move up a setting. If he does so, he gets $10,000, but he can never permanently return to a lower setting. Like most of us, the self-torturer would like to increase his fortune but also cares about feeling well. Since the self-torturer cannot feel any difference in comfort between adjacent settings but gets $10,000 at each advance, he prefers, for any two consecutive settings s and s+1, stopping at s+1 to stopping at s. But, since he does not want to live in excruciating pain, even for a great fortune, he also prefers stopping at a low setting, such as 0, over stopping at a high setting, such as 1000
This passage as stated states that the increments to be increased are of the devices settings (i.e. amount of electric current). But the "puzzle" seem to arise when we consider increments of degrees of pain.
But pain is dependent not simply on one factor such as external stimulation from electric currents. It is a function also of psychological factors. Psychological experiments over the years have shown that individual's pain tolerance and subjective evaluation of the degree of pain vary considerably based on the individual's state of mind at the time. People may experience more pain and tolerate more pain such as electric shocks or having their hand immersed in ice water simply by changing a state of mind either self-induced or by the experimenter or through some uninduced capricious change of the state of the mind. Thus the agent may experience two shocks with very small differences in electric current as drastically different in subjective pain.
So the agent may not be able to predict when his state of mind changes for the worse making him vulnerable to experience an intransitive and unbearable rise in pain in that incremental series of electric current. When it does happen it will be experienced as a pain that is noticeably greater than the pain resulting from the shock administered immediately before.
I think that many philosophical puzzles of rational choice such as Slote's "Satisficing maximizer" can also be solved by appealing to principles of unpredictability and context instability like I have here.