This study deals with psychological correlates of long-term imprisonment on a representative sample of 175 men serving either indeterminate sentences or determinate sentences of 10 yrs or more in a number of English prisons. 4 groups of prisoners were delineated, matched for age but differing in mean total length of prison experience, and a battery of cognitive tests was administered to each S. Analysis of the data showed no decline in general intellectual capacity with increasing length of imprisonment, but hostility and introversion increased significantly. A group of men who had been released on parole subsequent to testing did not differ significantly on these measures from a matched group who had been considered for parole but detained for a further period. This fact is interpreted as supporting the hypothesis that imprisonment, rather than selection procedures, was responsible for the differences noted.
British Journal of Criminology,
Vol. 13, no. 4 (Oct 1973), pp. 312-330