We don’t flog people in our prison system, or put them in thumbscrews or stretch them on the rack. We do, however, lock prisoners away in social isolation for 23 hours a day, often for months, years or decades at a time.

We prohibit the former and permit the latter because we make a distinction between physical and social pain. But, at the level of the brain where pain really resides, this is a distinction without a difference. Matthew Lieberman of the University of California, Los Angeles, compared the brain activities of people suffering physical pain with people suffering from social pain. As he writes in his book, “Social,” “Looking at the screens side by side ... you wouldn’t have been able to tell the difference.”

The brain processes both kinds of pain in similar ways. Moreover, at the level of human experience, social pain is, if anything, more traumatic, more destabilizing and inflicts more cruel and long-lasting effects than physical pain. What we’re doing to prisoners in extreme isolation, in other words, is arguably more inhumane than flogging.

Yet inflicting extreme social pain is more or less standard procedure in America’s prisons. Something like 80,000 prisoners are put in solitary confinement every year. Prisoners isolated in supermaximum facilities are often locked away in a 6-by-9-foot or 8-by-10-foot barren room. They may be completely isolated in that room for two days a week. For the remaining five, they may be locked away for 23 hours a day and permitted an hour of solitary exercise in a fenced-in area.