Keywords: NOMAPs, research

Short Explanation, short comment, questions

Gieles, Frans E. J.
Type of WorkComment on an article

Pornography Use and Sexual Aggression: The Impact of Frequency and Type of Pornography Use on Recidivism Among Sexual Offenders
Drew A. Kingston, Paul Fedoroff, Philip Firestone, Susan Curry, and John M. Bradford. AGGRESSIVE BEHAVIOR, Volume 34, pages 1–11 (2008).

By: Frans E. J. Gieles, PhD, The Netherlands, 2021

Short Explanation

It is a quite difficult article, at least for the average student and Ipce reader.

  • The original lay out is a sea of letters nearly without any white line or list. Thus, I have made a more simple “Quotes from …” version. 
  • The statistics used are quite complex and not explained. Thus, I have made this short explanation

Static 99

This is a method to predict the likelihood of offending or re-offending of a person.
The method make a difference between

  • Static factors: these cannot be changed, e.g. age, and 
  • Dynamic factors: these can be changed, e.g. opinions.


A statistic value, e.g. p = the likelihood that a prediction is true, usually not only for the sample, but also for the population; usually noted with the Confidence Interval, CI, mostly chosen as 95%, within which the value will be found by repeated research.

Regression analysis

A statistic method to calculate and prove that two factors are connected, usually

  • x as an independent factor (e.g. age or independent groups) and
  • y as a dependent factor, that influences the independent factor (e.g. knowledge).

The χ2 test

Frequently used in the article. It is a statistical method to calculate and proof the differences between two independent groups.
In the article the Static 99 prediction (low, medium, high) and re-offending is chosen as the first level or block; the prediction is said to be significant.
Then, the authors add

  • ‘pornography use’ to the analysis in Block 2, and
  • ‘re-offending’ also in Block 3, to see if the χ2  changes.

The added category is than hold as responsible for the change.

Effect size

The researcher tests several possible working (intervening, moderating) factors that influence a phenomenon. Then, the degree of the influence of those factors is calculated as Effect Size.

A famous example is the research of the Rind .e.o. team, searching for effects of sexual experiences during childhood on the degree of well-being during adulthood. It appeared that

  • the factor ‘sexual experience’ could declare 1% of the variance during adulthood, but that
  • the factor ‘family environment’ (read: problematic family environment) declared 10% of the variance,

thus the latter has ten times more influence (effect size) than the former.

The effect size is in the article mentioned as “Chohen’s d´.

Some remarks and comments

“Deviant pornography”

This concept is defined as “any self-reported use of pornography containing children and/or violence.”

Problem 1:
This definition is, in my opinion, too broad, because of the “and/or” combination of “children” and “violence”. In a research project with 341 “child molesters” the connected notion of “children” and “pornography” is a possibly important  connection, at least in the hypothesis. Adding “violence” to the definition makes it unclear, which type of pornography the respondents have seen.
Moreover, at least not all ‘child pornography’ is also ‘violent pornography’. ‘Child pornography’ can also simply show nudeness, which is not the same as ‘violence’. Viewing nudeness can be illegal thus guilty, but can also be innocent.

Problem 2:
The concept deviant refers to the concept normal, but in a forensic context it actually refers to the concept illegal, which changes the psychological category ‘deviant’ into a juridical category ‘illegal’. An act, seeing images, is illegal if a law declares it as illegal and as a judge has confirmed this.
But laws continually change and are quite different by state and time. What was legal in 1985 may be illegal in 1990, in 2008 pr 2020.

For example, the definition of child pornography, thus illegal, has changed in many states after the Lanzarote Congress of 2007 and the Lanzarote Convention of 2010, after which e.g. the Dutch Minister of Justice in 2016 has changed the definition of illegal child pornography.


The Static 99 test is said to give a quite trustable prediction of (re-)offending because of a trustable high correlation between the score and the later offending. . Logically, neither the test, nor the score causes the (re-)offending. The scores only predict. The causes or sources of the (re-)offending are the factors measured by the test, thus the characteristics, the history and situation of the person tested.

Does the use of (deviant) pornography predict re-offending? Yes, the frequency at least for the high-risk offenders, and the type more or less for all offenders.
Again, the scores of the frequency and the type of pornography seen may predict re-offending, but cannot be said to cause re-offending. Viewing (child)pornography is  maybe not more than a trigger of an underlying already present and active source of cause. The first offending, the use of (deviant) pornography and the re-offending must have common cause or source, supposedly being lust and lack of self-discipline. As the authors say it:

“pornography may simply accelerate a process that is already underway.”
Thus, the reader should not read or interpret ‘predicts’ as ‘causes’. 

The reader should also know that such a prediction is not more than a chance of re-offending.


What to do? (1)

What to do if a person, convicted or not, appears to use child pornography?

  • Tell him that this raises the chance of (re-)offending because this is “scientifically proven”?Proved by which kind of science: only by statistic, thus quantitative research?
  • Thus arrest the person, force him to accept treatment or a clinic, if not a jail?

This is a difficult question with psychological as well as juridical and ethical connotations.

For help or treatment, there is more needed than statistic quantitative research; needed is qualitative research to the motives, characteristics, cognitions, feelings, abilities en more of those people.

Which people? Only the convicted offenders, but better (also) the non-convicted people, the non-offenders, nowadays called the “NOMAPs”: Non Offending Minor Attracted Persons”.

What to do? (2)

New research is needed because the situation anno 2021 is very different from the situation 1982 – 1992. Pornography in the latter era was difficult to reach in more or less hidden shops or parts of shops, nowadays it is easily reachable for everyone on the Internet – a quite different situation, as the authors already recognize.

In our era, scientists have acknowledged that too much research on ‘pedophilia’ actually has been research to ‘pedosexuality’, which is not the same.

Thus, new research should be about ‘pedophilia’ as a legal feeling or desire, not about ‘pedosexuality’ as an illegal way of acting.
Thus, new research might be about the NOMAPs, mentioned here above. Also, research should be not one-sided about possible offending, but about helping the person if he or she asks for help to live in a legal, social, and even quite happy way with pedophilic feelings or, better, not being by definition a disorder but an orientation.

How to do such research?

With the NOMAPs as respondents, there have supposedly not been offending acts, thus no re-offending, and supposedly few or no use of (child)pornography, thus the design of the research in the article of Kingston a.o. is not usable. Quantitative data are not known. Thus, a qualitative design will be the best. Don't count the people, listen to the people.