Suppose that Sensitive and Insensitive commit the same crime, under the same circumstances. They are both convicted and sentenced to spend four years in identical prison facilities. In fact, their lives are alike in most respects, except that Sensitive is tormented by prison life and lives in a constant state of fear and distress, while Insensitive, living under the same conditions, finds prison life merely difficult and unpleasant. Though Sensitive and Insensitive have sentences that are identical in name—four years of incarceration—and the circumstances surrounding their punishments appear identical to a casual observer, their punishment experiences are quite different in severity.
Many theorists provide a retributive justification for punishment. They believe that offenders deserve to suffer for their crimes. They typically also believe that an offender’s suffering should be proportional to the seriousness of his offense. For example, murderers should be punished more than thieves, who should be punished more than jaywalkers. Sensitive and Insensitive, however, have committed crimes of equal seriousness, and, on this view, they should suffer the same amount. In this example, they don't. Most retributivists seem committed to the perhaps surprising outcome that we ought to take account of the differences in the punishment experiences of people like Sensitive and Insensitive.
The response that Sensitive and Insensitive should receive equal punishments for equal crimes is not itself a challenge to the calibration view. At issue is, "What does it mean to have an equal punishment?" My claim here is that the only plausible way to understand retributivist suffering is in terms of experiential suffering; so that's what would need to be equalized (if you think punishments should be equal for identical crimes).
Many consequentialist punishment theorists believe that we should punish in order to deter crime, incapacitate offenders, and rehabilitate criminals. They do not seek to maximize punishment because punishment itself has negative consequences. Among those negative consequences, many consequentialists would quite directly incorporate offenders’ negative subjective experiences into their assessments of the costs of punishment. So a cost-benefit analysis of punishing Sensitive will likely look different than a cost-benefit analysis of punishing Insensitive.
More generally, consequentialists cannot optimize their deterrence strategies without taking account of different people’s anticipated subjective experiences. A group of people who are very sensitive to the risk of suffering in prison are likely to be optimally deterred at a different level than people who are very insensitive to the risk of suffering in prison. A world with calibrated sentences makes it easier to optimally deter a larger number of people. Therefore, absent concerns about cost and administrability, consequentialists are also committed to the view that we ought to consider the differences in the punishment experiences of people like Sensitive and Insensitive.
But what about the very important concerns about cost and administrability? And how does this topic relate to neuroscience? Stay tuned . . . (The text above is adapted from this draft article. Law review editors interested in the piece are invited to contact me.)