Andrew Gumbel explains:
Prisoners going into solitary [confinement] sometimes imagine they can take advantage of their isolation to read, or study, or develop an interest in painting, but, invariably, they grow listless and unfocused within just a few days — unable to concentrate for even short periods of time. In a 2003 paper, Craig Haney of the University of California, Santa Cruz noted: “There is not a single published study of solitary or supermax-like confinement in which nonvoluntary confinement lasting for longer than 10 days […] failed to result in negative psychological effects.”
The evidence of these studies clearly contradicts the official line that isolating prisoners is a necessary measure to reduce prison violence.
Violent incidents at California prisons have actually increased by almost 20 percent since Pelican Bay opened and long-term isolation became institutionalized statewide. When a national commission spearheaded by a retired federal appeals judge and a former US attorney general looked into the matter in 2006, they concluded that responsibility for prison violence lay primarily with the prison authorities, not the prisoners themselves. A system that either packs prisoners into overcrowded cells or isolates them, then fails to provide an adequate daily structure of work, exercise, reading and socializing, is a system ready to explode.