The inability to switch the POA during an ongoing activity when an interruption or an intervening circumstance requires such a switch is one of the most characteristic signs of frontal lobe system (FLS) dysfunction. The latter is manifested by relatively deficient myelination of frontal lobe pathways on the one hand and specially deficient action behavior on the other. The other major sign, the inability to plan, is apparently outgrown during childhood. In addition to its identification in normal children and youths charged with indictable acts, FLS dysfunction apparently is manifested by some criminals, according to clinical observations. Therefore, it is hypothesized that a previously unidentified subgroup exists among apparently normal young adult offenders who are unable to switch POA within a hierarchy of principles and that they will be revealed by the already established Trail Making Test B (TMT-B) and by the new brief clinical Narratives Test (NT). The test results on 30 criminals corroborate the hypothesis. On the NT, 36 percent, and on the TMT-B, 33 percent of young adult men charged with criminal acts (serving sentences of up to 2 years) demonstrated specifically immature action behavior indicative of FLS dysfunctioning. Probable etiological factors include a developmental lag in the myelinization of the frontal lobes, such as is associated with deprivation of practice in functioning; however, pathology, particularly due to trauma, has yet to be ruled out. Practical applications of this possible physiolgical dysfunction include prescribing remedial exercises to cope with FLS dysfunction. Twenty-six references are provided. (Author abstract modified)