Subsequently I met with the nurse, who explained to me that most of the residents were suffering from Post Traumatic Stress Disorder (PTSD) and that it was well documented that PTSD severely impairs one's ability to do math.
A recent Stonehill graduate and I agreed to work with him, and for the next two years she and I visited the SCI unit periodically and worked with him (I worked on math and she worked on everything else - she spent much more time there than I did). As it turns out, he was one of the best students I have ever had, with boundless curiosity and a great love of learning, but what the nurse told me was absolutely true.
I quickly learned that, after posing a math problem, I needed to wait paitiently for up to five minutes while he thought about how to solve the problem. I would say something like "If x+4 = 7, what is x?", and wait. He would think out loud, saying "x plus 4, x plus 4, that's 7". For the next several minutes, he would obviously be engaged in intense concentration, continuing to repeat the problem. After several minutes of strenuous effort, he would say "It's gotta be 3". He would almost always get the right answer, but it required a great deal of effort and will power.
Later I heard the keynote speaker at the Association for Psychological Science (APS) conference say that "We now know that with PTSD, the damage to the prefrontal cortex is severe and permanent".
This story has a happy ending. Through the efforts of my co-tutor, his situation came to the attention of Governor Duval Patrick, and he was presented with a well-deserved honorary GED.