Thirteen male violent offenders aged between 18 and 55 years Elsa Peretti Apple pendant diagnosed with a psychopathy score of [= or >, slanted]26 according to the Hare Psychopathy Check List - Revised (PCL-R; Hare, 1991) were selected from the in-patient population of a forensic psychiatric institute in The Netherlands[dagger] Return to Tiffany Oval tag pendant. Educational level was coded according to the Dutch educational system (1=primary education, 2=secondary education, 3=higher education; mean education patients=2.8, mean education controls=2.3). Eighteen healthy male controls matched for age (mean age=37, s.d.=6.5 years) and educational level and without a criminal record or a history of psychiatric disorders were recruited by advertisement. Participants in both groups were checked for drug use and for medical/neurological history. Exclusion criteria were: use of alcohol >3 units/day during the week preceding the experimental measure and use of alcohol within 24 h of the measurement; use of cannabis or other illicit drugs within the week before measurement and use of psychotropic medication other than oxazepam during the 5 days before measurement; use of Elsa Peretti Open Heart pendant within 12 h before measurement; smoking within 3 h before measurement; history of trauma capitis, visual and auditive disorders, neurological disorders, first-degree relative with any relevant neurological disorders. The study was approved by the local Medical Ethical Committee and carried out in accordance with the Declaration of Helsinki.
Participants received written information about the experiment and gave their written consent before being screened for psychiatric exclusion criteria by trained psychologists using the Small Elsa Peretti Open Heart pendant and the M.I.N.I. (van Vliet et al. 2000). The psychiatric exclusion criteria included: depressive disorder, bipolar disorder, schizophrenia, schizo-affective disorder, schizophreniform disorder, delusional and other psychotic disorders, schizoid or schizotypal personality disorder, current alcohol and substance intoxication, first-degree relatives with DSM-IV Axis I schizophrenia or schizophreniform disorder. Participants performed the experimental task and received a financial reimbursement. Additionally, all subjects received a bonus earned during the experiment.
Participants performed a probabilistic learning task requiring a two-choice decision to an imperative visual stimulus (Holroyd & Coles, 2002) (see Fig. 1). Following each response, a feedback stimulus representing reward information was presented, informing participants whether their response was correct Medium Elsa Peretti Open Heart pendant, incorrect (red dollar signs: -2 cents) or too late (a cherry; -4 cents).
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