Andreas Mokros

Behavioural crime linking in serial homicide

Abstract The present study aimed to identify dimensions of variation in serial homicide and to use these dimensions to behaviourally link offences committed by the same offender with each other. The sample consisted of 116 Italian homicides committed by 23 individual offenders. Each offender had committed at least two homicides. As some offenders had worked together and some murders involved more than one victim, there were 155 unique pairings of offenders and victims. Dichotomous variables reflecting crime features and victim characteristics were coded for each case. Using Mokken scaling, a nonparametric alternative to factor analysis, seven dimensions of variation were identified. Five of the dimensions described variations in the motivation for the killings. Three of these were concerned with aspects of instrumental motivation whereas two of the motivational scales described variations in sexual motivation. The two remaining dimensions dealt with the level of planning evident in the crime scene behaviour of the offender. Two dimensions were identified: one consisting of behaviours suggesting a higher level of control and another describing impulsiveness. Using discriminant function analysis with the dimensions as independent variables and the series an offence belonged to as dependent variable, 62.9% of the cases could be correctly assigned to the right series (chance expectation was 6.2%). The implications of the results for serial homicide investigations are discussed.

Diminished Cooperativeness of Psychopaths in a Prisoner's Dilemma Game Yields Higher Rewards

Maladaptive social behavior is one of the defining characteristics of psychopathic personality disorder. Nevertheless, maladaptive social behavior has only rarely been observed among psychopaths in experimentally controlled situations. The authors assessed the behavior of criminal psychopaths from high-security psychiatric hospitals in a computer simulation of a social dilemma situation. The psychopaths showed a markedly higher proneness to competitive (i.e., noncooperative) behavior than did healthy adults from the general population. The odds ratio between defection and being a psychopath was estimated at 7.86 in the sample. The probability to choose selfish instead of cooperative behavior was significantly linked to the following subscales of the Psychopathy Personality Inventory-Revised (S. O. Lilienfeld & M. R. Widows, 2005): rebellious nonconformity, Machiavellian egocentricity, and the total score. On average, the psychopathic participants accumulated higher gain and more strongly exploited their counterpart than did the healthy participants.

A Cumulative Scale of Severe Sexual Sadism

The article assesses the scale properties of the criterion set for severe sexual sadism in a sample of male forensic patients (N = 100). Half of the sample consists of sexual sadists; the remainder is sampled at random from the general group of nonsadistic sex offenders. Eleven of 17 criteria (plus the additional item of inserting objects into the victim’s bodily orifices) of Marshall, Kennedy, Yates, and Serran’s list form a cumulative scale. More specifically, this scale comprises all the 5 core criteria that Marshall and his colleagues considered particularly relevant. The resulting 11-item scale of severe sexual sadism is highly reliable (r tt = .93) and represents a strong scale (H = .83) of the Guttman type (coefficient of reproducibility = .97). The 11-item scale distinguishes perfectly between sexual sadists and nonsadistic sex offenders in the sample.

Psychopathy and Sexual Sadism

Psychopathic personality disorder and sexual sadism share several common characteristics, such as emotional detachment from the suffering of others or the preparedness to inflict pain or injuries. Based on a sample of 100 male forensic patients (all of them sex offenders, half of them sadistic), the concept of psychopathy and sexual sadism as a unified construct was tested empirically. Pooling indicator variables for psychopathic and sexually sadistic disorders showed that a two-factorial solution yielded a better fit than a single-factor model. The two factors identified psychopathy and sexual sadism as separate latent variables. More specifically, the data were compatible with a path model in which affective deficits and behavioral disinhibition of the psychopathy domain are precursors to sexually sadistic conduct.

Emotional empathy and psychopathy in offenders: an experimental study.

Previous studies associated psychopathy in adults with deficits in empathy but these studies did not directly compare cognitive and emotional facets of empathy. The present study sought to establish whether psychopathy is associated with impairments in emotional empathy among adult offenders. Participants were 90 male offenders scoring low (n = 29), medium (n = 33) or high (n = 28) on the Psychopathy Checklist-Revised (PCL-R) and n = 28 male noncriminal controls. Empathy functioning was assessed through self-report and computerized decision tasks, differentiating between perspective-taking (cognitive empathy) and compassion (emotional empathy). Against expectations, level of psychopathy among the offenders was not associated with either emotional or cognitive empathy. Offenders however had lower scores for both cognitive and emotional components of empathy functioning than controls. Both facets of empathy showed small but significant positive correlations with education level and social desirability. The methods employed to assess differences in empathy functioning may not be sensitive enough to assess differences in forensic samples.

Functional Cortical and Subcortical Abnormalities in Pedophilia: A Combined Study Using a Choice Reaction Time Task and fMRI

INTRODUCTION Pedophiles show sexual interest in prepubescent children but not in adults. Research into the neurofunctional mechanisms of paraphilias has gathered momentum over the last years. AIM To elucidate the underlying neural processing of sexual interest among pedophiles and to highlight the differences in comparison with nonparaphilic sexual interest in adults. METHODS Nine pedophilic patients and 11 nonpedophilic control subjects underwent functional magnetic resonance imaging (fMRI) while viewing pictures of nude (prepubescents, pubescents, and adults) and neutral content, as well as performing a concomitant choice reaction time task (CRTT). MAIN OUTCOME MEASURES Brain blood oxygen level-dependent (BOLD) signals and response latencies in the CRTT during exposure to each picture category. RESULTS Analysis of behavioral data showed group differences in reaction times regarding prepubescent and adult but not pubescent stimuli. During stimulation with pictures displaying nude prepubescents, pedophiles showed increased BOLD response in brain areas known to be involved in processing of visual sexual stimuli. Comparison of pedophilic patients with the control group discovered differences in BOLD responses with respect to prepubescent and adult but not to pubescent stimuli. Differential effects in particular occurred in the cingulate gyrus and insular region. CONCLUSIONS The brain response of pedophiles to visual sexual stimulation by images of nude prepubescents is comparable with previously described neural patterns of sexual processing in nonpedophilic human males evoked by visual stimuli depicting nude adults. Nevertheless, group differences found in the cingulate gyrus and the insular region suggest an important role of these brain areas in pedophilic sexual interest. Furthermore, combining attention-based methods like CRTT with fMRI may be a viable option for future diagnostic procedures regarding pedophilia.

Is pedophilic sexual preference continuous? A taxometric analysis based on direct and indirect measures.

The present study addressed the question of whether deviant sexual preferences for children can be considered a taxon, utilizing data from a multimethod assessment battery. The test battery comprised direct self-report as well as indirect latency-based measures (Implicit Association Tests, viewing time) of deviant sexual preferences for children. In a mixed sample of adult men (N = 304, including sex offenders against children, sex offenders against adults, and controls who were either nonsexual offenders or nonoffenders), 27% of the offenders convicted for child sexual abuse or child pornography charges were identified as a homogeneous and distinct latent class. Additional taxometric analyses corroborated the notion of a pedophilic subgroup. Individuals in this pedophilic group showed elevated scores on measures of deviant sexual preference for children over adults. The offense histories of the individuals from the pedophilic cluster indicated an increased likelihood of pedophilic preference as assessed by a file-based summary index. We interpret the results as evidence for pedophilic sexual preference as a distinct and taxonic clinical construct.

Assessing measurement invariance of PCL-R assessments from file reviews of North American and German offenders.

Cross-cultural research on psychopathy necessitates assessment methods that are generalizable across linguistic and cultural differences. Multiple-group confirmatory factor analysis was used to compare the factorial structure of Psychopathy Checklist-Revised (PCL-R) assessments obtained from file reviews of North-American (N=2622) and German (N=443) male offenders. The analyses indicated that the 18 item, 4-factor model of the PCL-R obtained with the standard PCL-R protocol (interview and file review) also holds for file review data. On a factor-by-factor level, the data are commensurate with strong factorial invariance of factor loadings and item thresholds for the Interpersonal and Lifestyle factors, and with likely metric invariance for the Affective factor. The Antisocial factor showed structural differences between the two samples. The results imply that cultural or environmental factors more strongly influence the judgment and/or expression of antisociality. Based on the results, cross-cultural comparisons between North-American and German offenders in terms of PCL-R psychopathy should be limited to the Interpersonal and Lifestyle factors. Further research using data obtained through the standard protocol (i.e., interview plus file information) is encouraged.

Evidence for Heritability of Adult Men's Sexual Interest in Youth under Age 16 from a Population‐Based Extended Twin Design

INTRODUCTION Sexual interest in children resembles sexual gender orientation in terms of early onset and stability across the life span. Although a genetic component to sexual interest in children seems possible, no research has addressed this question to date. Prior research showing familial transmission of pedophilia remains inconclusive about shared environmental or genetic factors. Studies from the domains of sexual orientation and sexually problematic behavior among children pointed toward genetic components. Adult mens sexual interest in youthfulness-related cues may be genetically influenced. AIM The aim of the present study was to test whether male sexual interest in children and youth under age 16 involves a heritable component. MAIN OUTCOME MEASURES The main outcome measure was responses in a confidential survey concerning sexual interest, fantasies, or activity pertaining to children under the age of 16 years during the previous 12 months. METHODS The present study used an extended family design within behavioral genetic modeling to estimate the contributions of genetic and environmental factors in the occurrence of adult mens sexual interest in children and youth under age 16. Participants were male twins and their male siblings from a population-based Finnish cohort sample aged 21-43 years (N = 3,967). RESULTS The incidence of sexual interest in children under age was 3%. Twin correlations were higher for monozygotic than for dizygotic twins. Behavioral genetic model fitting indicated that a model including genetic effects as well as nonshared environmental influences (including measurement error), but not common environmental influences, fits the data best. The amount of variance attributable to nonadditive genetic influences (heritability) was estimated at 14.6%. CONCLUSIONS The present study provides the first indication that genetic influences may play a role in shaping sexual interest toward children and adolescents among adult men. Compared with the variance attributable to nonshared environmental effects (plus measurement error), the contribution of any genetic factors seems comparatively weak. Future research should address the possible interplay of genetic with environmental risk factors, such as own sexual victimization in childhood.

Association between brain structure and phenotypic characteristics in pedophilia

Studies applying structural neuroimaging to pedophiles are scarce and have shown conflicting results. Although first findings suggested reduced volume of the amygdala, pronounced gray matter decreases in frontal regions were observed in another group of pedophilic offenders. When compared to non-sexual offenders instead of community controls, pedophiles revealed deficiencies in white matter only. The present study sought to test the hypotheses of structurally compromised prefrontal and limbic networks and whether structural brain abnormalities are related to phenotypic characteristics in pedophiles. We compared gray matter volume of male pedophilic offenders and non-sexual offenders from high-security forensic hospitals using voxel-based morphometry in cross-sectional and correlational whole-brain analyses. The significance threshold was set to p < .05, corrected for multiple comparisons. Compared to controls, pedophiles exhibited a volume reduction of the right amygdala (small volume corrected). Within the pedophilic group, pedosexual interest and sexual recidivism were correlated with gray matter decrease in the left dorsolateral prefrontal cortex (r = -.64) and insular cortex (r = -.45). Lower age of victims was strongly associated with gray matter reductions in the orbitofrontal cortex (r = .98) and angular gyri bilaterally (r = .70 and r = .93). Our findings of specifically impaired neural networks being related to certain phenotypic characteristics might account for the heterogeneous results in previous neuroimaging studies of pedophilia. The neuroanatomical abnormalities in pedophilia seem to be of a dimensional rather than a categorical nature, supporting the notion of a multifaceted disorder.