Experimental investigation to identify neuropsychological impairment in convicted paedophile offenders

Abstract

BACKGROUND. Neuropathological processes affecting the left frontotemporal lobes and their connections with subcortical structures have been reported in individuals who sexually assault minors. However, these findings are not necessarily conclusive, and knowledge is limited as to how such factors influence the 'blocking' adult sexual relations, disinhibition, emotional congruence and sexual arousal to children; or indeed if functional disorders are more significant. METHOD. A combination of neuropsychological (LNNB Form II) and personality (MMPI-2) probes where used to ascertain the profiles of male subjects satisfying DSM-III criteria for paedophilia, and a comparison was made with male rapist and homicide offenders to identify a characteristic neuro-behavioural syndrome. All groups were matched for premorbid intelligence, drug/alcohol abuse, socio-economic status and incarceration period. Hypotheses of greater dysfunction localised to the lefthemisphere fronto-temporal lobe areas, and more disturbed personality and psychopathology in the paedophile offenders were tested. The Multiphasic Sex Inventory (MSI) was also used to confirm the diagnoses of the sexual offenders and to assess psychosexual functioning. RESULTS. The offender groups were undifferentiated in terms of frequency of overall neuropsychological dysfunction, yet 26.8 per cent had clinically significant cognitive impairment, and a further 23.2 per cent were diagnosed as 'Borderline.' However, pattern of expressive speech and writing deficits in the paedophile group's LNNB-11 profile was consistent with subclinical features of Transcortical Motor Aphasia-Type I syndrome (i.e. non-fluent verbal output - decreased spontaneity of expression and impoverished narrative speech, but with intact comprehension, repetition of spoken language; clumsily produced letters and hypereconomy of written content; and apathy). Damage to the left-hemisphere dorsolateral prefrontal cortex (DLPFC) is known to be associated with this type of aphasia, which in tum increases the probability of dysexecutive syndrome (i.e. limited planning and maintenance of goal-directed behaviour and behavioural flexibility). The impact of this syndrome was clearly reflected by socialdeficit type features found in the paedophile's MMPI-2 48' /84' profile which are consistent with a schizotypal personality disorder (i.e. apathy, social withdrawal, constricted affect, odd speech and behaviour). Additionally, psychosexual functioning, rationalisations and cognitive distortions relating to offence behaviours was found to be more deviant in paedophiles than rapists. CONCLUSION. From a developmental perspective, neuropathology of the circuits connecting the dorsolateral prefrontal cortex with sub-cortical areas, presenting as dysexecutive syndrome, may be significant in explaining the paedophile' s lack of adjustment to, indifference for, and alienation from the adult world; increasing the probability for emotional and sexual dependency on children. Several possibilities for future research are identified and practical uses for the findings of this study are presented.