Which example of research with prisoners would be allowable under the regulations?

The example of examining age at first arrest as a predictor of adult criminal history is allowable under the regulations primarily because it focuses on a correlational study design that does not involve exposing participants to additional risks or interventions. This type of research typically involves the analysis of existing data or retrospective studies, which are often less invasive and do not subject the prisoners to harmful conditions. The focus here is on understanding patterns and associations rather than inducing any change in behavior or treatment.

In contrast, the other options involve specific interventions, direct comparisons, or studies that could be perceived as placing more significant psychological or physical burdens on the participants. For example, studying the effects of rehabilitation programs on juvenile delinquents may require active involvement and could raise ethical concerns regarding consent and coercion, especially in a vulnerable population. Similarly, comparing psychological effects of incarceration between different age groups might introduce variables that complicate informed consent and psychological safety. Research on recidivism rates, while informative, may also involve sensitive topics that require careful ethical considerations regarding the potential implications for the individuals involved. Thus, option A stands out for its compatibility with ethical research practices in regard to working with prisoners.