 One theory is that social groups are formed to reduce the discomforts of incarceration, and are therefore directly caused by the nature of imprisonment, while others believe that personal experience and the structure of each particular institution have more impact on inmate social structure.Additionally, some scholars believe that social groups form differently in male and female populations, while others hold that groups are fundamentally the same in men's and women's prisons.Charles Tittle conducted a study of inmate social groups in a Federal hospital serving a large groups of prisoners suffering from narcotics addiction in 1969, in which he compared the experiences of female inmates to those of the males.