A study by German scientists shows that it may be possible to identify paedophiles by scanning their brains as they look at pictures of adults and children
The differences in brain activity could pinpoint who was a paedophile and who was not at a rate of roughly 90 percent, according to the study.
The research, which involved professors from universities in Kiel, Berlin and Denmark, may have ground-breaking uses in the treatment of sex offenders, said Jorge Ponseti, one of the study's authors at the Christian Albrechts University of Kiel.
It is important to verify whether a first-time sex offender is truly a paedophile – in other words having an inherent attraction to prepubescent children – or merely committed a crime of opportunity, because treatment strategies are different for both groups Ponseti said.
“You can offer a paedophile drugs to lower sex drive or teach him in psychotherapy to avoid situations involving children, but you waste your time if you explain how to have a relationship with adult women,” Ponseti said. “You can approach someone who is not a true paedophile differently. It is important to know what kind of sex offender this is.”
Current techniques to determine whether someone is a paedophile, such as by using a device attached to the penis to measure arousal levels, are notoriously imprecise and not widely used in Germany. Some paedophiles are able to fool such devices by controlling their arousal levels.
Ponseti said he thinks the fMRI technique will be much more precise, although researchers are currently developing another study to see whether its possible for paedophiles to somehow fool it.
“Brain response to an emotional stimulus is very fast and it happens most likely before conscious acknowledgement of a picture takes place, so I think it is unlikely that faking will be successful,” Ponseti said.
Assessment of Pedophilia Using Hemodynamic Brain Response to Sexual Stimuli
Jorge Ponseti, PhD; Oliver Granert, MSc; Olav Jansen, Prof MD; Stephan Wolff, MSc; Klaus Beier, Prof MD, PhD; Janina Neutze, MSc; Günther Deuschl, Prof MD;Hubertus Mehdorn, Prof MD; Hartwig Siebner, Prof MD; Hartmut Bosinski, Prof MD
Arch Gen Psychiatry. Published online October 3, 2011. doi:10.1001/archgenpsychiatry.2011.130
Context Accurately assessing sexual preference is important in the treatment of child sex offenders. Phallometry is the standard method to identify sexual preference; however, this measure has been criticized for its intrusiveness and limited reliability.
Objective To evaluate whether spatial response pattern to sexual stimuli as revealed by a change in the blood oxygen level–dependent signal facilitates the identification of pedophiles.
Design During functional magnetic resonance imaging, pedophilic and nonpedophilic participants were briefly exposed to same- and opposite-sex images of nude children and adults. We calculated differences in blood oxygen level–dependent signals to child and adult sexual stimuli for each participant. The corresponding contrast images were entered into a group analysis to calculate whole-brain difference maps between groups. We calculated an expression value that corresponded to the group result for each participant. These expression values were submitted to 2 different classification algorithms: Fisher linear discriminant analysis and -nearest neighbor analysis. This classification procedure was cross-validated using the leave-one-out method.
Setting Section of Sexual Medicine, Medical School, Christian Albrechts University of Kiel, Kiel, Germany.
Participants We recruited 24 participants with pedophilia who were sexually attracted to either prepubescent girls (n = 11) or prepubescent boys (n = 13) and 32 healthy male controls who were sexually attracted to either adult women (n = 18) or adult men (n = 14).
Main Outcome Measures Sensitivity and specificity scores of the 2 classification algorithms.
Results The highest classification accuracy was achieved by Fisher linear discriminant analysis, which showed a mean accuracy of 95% (100% specificity, 88% sensitivity).
Conclusions Functional brain response patterns to sexual stimuli contain sufficient information to identify pedophiles with high accuracy. The automatic classification of these patterns is a promising objective tool to clinically diagnose pedophilia.