Having spent a considerable portion of my adult life imprisoned, I don't think the contact with other criminals increases a person's penchant for criminality. I think the incarceration itself does though by essentially fucking your entire life up and resetting you to a hard zero. And while you are inside you are not making any improvement to your life, e.g. skill building, improving your emotional intelligence; and in fact you are usually letting any skills you might have had stagnate and deteriorate beyond use.