nextgenforensic

Examining preferential pedophilic interest as a risk factor for sexual recidivism

By Ian McPhail (@IanVMcPhail on twitter)

In my last two posts on nextgenforensic, I reviewed what we know about the latent structure of pedophilic interests and then examined the implications of this research by looking to see if non-preferential pedophilic interest was a predictor of sexual recidivism (tldr: it was not).

As a quick recap, my colleagues and I recently found, in five samples of men convicted of sexual offences, that the latent structure of pedophilic interest could be best characterized as: some men non-pedophilic; some men are non-preferentially pedophilic; and some men are preferentially pedophilic (that is, they have much greater interest in children compared to adults).

A further finding in our study was that the non-pedophilic and non-preferentially pedophilic men had about the same rate of sexual recidivism, while the preferentially pedophilic men had much higher rates of sexual recidivism.

This result was surprising because people in the field tend to think of pedophilic interest as a risk factor: that is, if a sexual offender has pedophilic interests, he is at higher risk to continue to commit sexual offences, even after he is released from prison after being incarcerated for a sexual offence. If this view is correct, we would have expected to see recidivism rates that are higher in both pedophilic classes of men, not just the preferentially pedophilic men.

Because this was not the case in our sample, and I was interested to follow-up on it, my last post looked at the past scientific literature looking at sexual recidivism rates in non-pedophilic sex offenders and non-preferentially pedophilic sex offenders. When I combined the results from five studies, the difference in sexual recidivism rates was basically nil. Taking stock of the evidence from the past research, I concluded that non-preferential pedophilic interest is not a risk factor for sexual recidivism.

In this post, I want to examine whether preferential pedophilic interest is a risk factor for sexual recidivism. I think what we find will have implications for the validity of the latent structural results my colleagues and I recently reported and will also further our understanding of whether pedophilic interest is indeed a risk factor for sexual recidivism.

Testing whether preferential pedophilic interest is a risk factor for sexual recidivism

Let’s take a look at the previous research that has examined whether preferential pedophilic interest predicts sexual recidivism by convicted sexual offenders. The results from five studies examining whether preferential pedophilia is related to sexual re-offending are presented in the table below.

Study Assess-ment method N d Rate in Non- Pedophilic Offenders Rate in Preferential Pedophilic Offenders
Beier (1998) DSM 35 1.310 30.8% 81.8%
Wilson et al. (2011) PPG 90 0.430 8.8% 17.9%
Eher et al. (2010) DSM 127 0.629
Eher et al. (2015) DSM 189 0.622
McPhail et al. (2018) PPG 210 0.491 29.1% 50%
Meta-analytic average 651 0.614

Here’s a short guide for the results table. The first thing to point out is that the men in these studies have all been convicted of a sexual offence. The studies examined rates of sexual re-offending after these samples of men were released from custody after serving a sentence for a sexual offence. I provided more detail on the importance of and methodology used in this kind of research in my last post.

The names of the authors of the study are in the first column.  The second column provides the measurement method used to diagnose pedophilic interest. I included here studies that used two methods of diagnosing pedophilia: the Diagnostic and Statistical Manual of Mental Disorders (labelled “DSM” in table) and phallometric testing (labelled “PPG” in the table).  These two methods are routinely used to identify pedophilic interests and represent reasonable measures of this sexual interest. One thing to note is that the DSM criteria measures whether someone is exclusively attracted to children, which means they have very little or no interest in adults. In contrast, the phallometric tests typically identify whether someone is preferentially attracted in children, which means that while they are most strongly attracted to children, they may still have a substantial interest in adults. I use the term “preferential” to capture both states of affairs.

[T]he re-offence rates in the preferentially pedophilic samples are basically double the rate of the non-pedophilic samples.

In the third column, the total sample size is given.  In the fourth column, the standardized mean difference is provided (i.e., d).  This statistic is a way of quantifying the difference in rates of re-offending between preferentially pedophilic and non-pedophilic men (the sexual recidivism rates for both groups are provided in the last two columns). To help interpret this statistic, a positive d value indicates higher sexual re-offence rates by preferentially pedophilic men.  A d of 0 means no difference in rates of sexual re-offence.  And a negative d indicates higher sexual re-offence rates by the non-pedophilic men. If preferential pedophilic interest is a risk factor that predicts sexual recidivism, we expect the d to be positive.

The consistent finding is that preferential pedophilia predicts sexual re-offending. When I compute a meta-analytic average that combines the ds for these five studies (the last row of the table), the average difference in sexual re-offending between these two groups is relatively large (d = 0.614). Even though the overall rate of recidivism was somewhat different across the studies, all the d values are well above 0 and the re-offence rates in the preferentially pedophilic samples are basically double the rate of the non-pedophilic samples.

Preferential pedophilic interest is a risk factor for sexual recidivism

Those are the data, but what does it all mean?

[Preferential pedophilic interest] is among the best predictors we have identified to date

First off, the meta-analytic average is rather large, which suggests preferential pedophilic interest is a strong predictor of future sexual recidivism in convicted sexual offenders. Just how large is this effect? An average d of 0.61 is larger than almost all other risk factors for sexual recidivism that have been studied in meta-analyses to date. For example, in a meta-analysis that looked at a large number of risk factors, the strongest predictor of sexual recidivism was not complying with the conditions of probation/parole, with a d of 0.62. In that meta-analysis, most risk factors’ d values were under 0.25. Further, a d of 0.61 is even larger than some well-established risk assessment measures, which are comprised of multiple items.

Comparing the predictive ability of preferential pedophilic interest to other risk factors, and even well-validated risk scales, makes it clear that it is among the best predictors we have identified to date.

Another heuristic we can use to assess what this average effect means is to see whether preferential pedophilia can be considered an “empirically supported risk factor”. A so-called empirically supported risk factor is one that has been studied 3 or more times and reasonably differentiates between re-offending and non-re-offending people. In the language of statistics, “reasonable” means when a meta-analysis of these studies is performed, the aggregate standardized mean difference (d) is at least |0.15| or greater. A simple comparison shows that preferential pedophilic interest meets these two criteria.

These findings I’ve presented suggest that preferential pedophilic interest is an empirically supported risk factor for sexual recidivism.

Putting it all together

To end this series of posts, I want to weave together what we have seen thus far.

It is reasonably safe to conclude that having a non-preferential sexual interest in children is not a risk factor for sexual recidivism. This may be a potentially surprising finding to some and one that poses a series of problems for the field and current clinical practice. The problems involve how to evaluate the level of risk a sexual offender poses when they experience pedophilic interest, but where their interest in prepubescent children is not preferential or exclusive. I would suggest the position that is supported by the evidence would be to conclude men with non-preferential pedophilic interest are not at elevated risk to re-offend. The data support this conclusion, even if it offends common-sense.

These two sets of results argue strongly in favor of clinicians and researchers always assessing whether pedophilic interests are exclusive or preferential.

Next, the value of considering whether pedophilic interest is exclusive or preferential is further supported by the robust and strong predictive relationship between preferential pedophilic interest and sexual recidivism. These two sets of results argue strongly in favor of clinicians and researchers always assessing whether pedophilic interests are exclusive/preferential or not. In clinical practice, to not do so may be unfair to the offender being evaluated and to potential victims. In research, not doing so may lead to inaccurate or misleading research results (which, in its own way is unfair to the participants of the research and the public that pays for the research).

Last, one of the main reasons I wrote this series of blog posts was to explore the implications of empirical examinations into the latent structure of pedophilic interests. This was a goal of mine because latent structural research is fairly abstruse, due to the complex statistics and methodological considerations involved. At first glace, research into latent structure of pedophilic interest appears to have very little to do with day-to-day clinical practice or future research efforts. The data presented in these three blog posts indicate that applying findings on the latent structure of pedophilic interests might have immediate and rather dramatic impacts on how we measure and understand pedophilic interest in sexual offenders.

McPhail, I. V. (2018, December 15). Examining preferential pedophilic interest as a risk factor for sexual recidivism [Weblog post]. Retrieved from https://nextgenforensic.wordpress.com/2018/12/15/examining-preferential-pedophilic-interest-as-a-risk-factor-for-sexual-recidivism/

 

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