Does prison work?
Does it change people and prevent crime?
Is punishment an effective way to change people's behavior?

I recently read "On the Effectiveness of Prison as Punishment" by Stuart Henry, Ph.D. from http://www.is.wayne.edu/stuarthenry/Effectiveness_of_Punishment.htm

This is what I learned:

"Psychological research on punishment in has shown that mild punishment can be effective in changing behavior, but the evidence is less clear about the effectiveness of severe punishment. Effectiveness of punishment is increased by:
1. Frequency of application
2. Immediacy of application
3. Punishment used in conjunction with positive reinforcement of pro-social behavior

However, punishment, especially in its severe form has several negative effects:
1. Avoidance or escape
2. Alienation of those punished, to the point of inaction
3. Aggressiveness, both targeted and generalized, by those punished
4. Conditioning of the punishers through rewarding them for behavioral change
5. Reproducing punishment behavior in those punished"

Looking at the incarceration of drug offenders, punishment is not a good strategy to use according to this research. First, punishment for the crime is not frequent, immediate, or used along with positive reinforcement for desired behaviors. Also, punishment promotes a gap between offenders and society in the forms of alienation, avoidance, and resentment.