My experience is that a very high proportion of offenders have learning disabilities and/or mental health problems plus a difficult unhappy life experience. Genuine rehabilitation is most unlikely. It would be so much better if the life circumstances of these people had been such that the situations leading to their imprisonment simply didn't arise. There's research indicating that a percentage have specific language difficulties which can lead to lack of comprehension of situations and implications for behaviour. Additionally, if they could express their thoughts more clearly, it would reduce the likelihood of an instant recourse to violent reaction. I believe that prisons are now employing Speech and Language therapists. Also, now I come to think of it, the introduction of a good nutritional diet has been found to have a beneficial effect on behaviour in young offenders.