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1. Abel, G. & Harlow, N., The Stop Child Molestation Book, Xlibris, 2001.

2. Carroll, R.T., "Penile plethysmograph," Skeptic's Dictionary, March 1, 2006.

3. Burton, D. & Smith-Darden, J., 1996 Nationwide Survey of Treatment Programs & Models, Brandon, VT: Safer Society Foundation, 2000.

4. Burton, D. & Smith-Darden, J., North American Survey of Sexual Abuser Treatment and Models 2000, Brandon, VT: Safer Society Foundation, 2001.

5. Center for Sex Offender Management, "Understanding Juvenile Sexual Offending Behavior," December 1999.

6. Goldin, R., "Lie Detector Tests," Statistical Assessment Service, May 2006.

7. Peters, J.M., “Using the Abel Assessment for Sexual Interest to Infer Lack of Culpability in a Criminal Case,” American Prosecutor's Research Institute Update, Vol. 14, No. 12, 2001.

8. Righthand, S. & Welch, C., "Juveniles Who Have Sexually Offended," U.S. Office of Juvenile Justice and Delinquency Prevention, March 2001.

9. Yankowski, L., Testimony to the Arizona Senate's Committee on Children's Psychological Treatment Programs, September 16, 1992.

Ethical Treatment for All Youth
Email: etay@ethicaltreatment.org

About the author


When children or teenagers are identified as possibly deviant or offending, police or therapists often attempt to find out what kinds of stimuli sexually arouse them. Although interviewers may ask them directly, children facing the prospect of being labeled as sexually deviant are reluctant to answer honestly. Therefore, presumably objective means are often used: sexual interest tests, polygraphs, and/or plethysmographs.

Sexual Interest Tests

A sexual interest test involves showing a person photographs of adults and children and measuring their visual reaction time in order to determine who they are sexually interested in. The only such test available is the Abel Assessment of Sexual Interest (AASI). The developer of this test explains, “The test-taker, who remains in street clothes, sits at a desk in front of a computer. The computer measures his sexual interest in pictures of children and adults dressed in bathing suits, as the test-taker would see them at the local swimming pool...This test is suitable for early diagnosis and is designed to be acceptable to the family of a 12-year-old child.”1

Scientists, however, do not accept the AASI as valid. It has never been tested on a representative sample of American children to determine what normal and abnormal responses would be. Assistant United States Attorney James M. Peters writes:

The developer withholds as 'trade secrets' data that might be analyzed and replicated, a factor that confounds rigorous scientific review...studies upon which the first phase of the AASI is based have used penile plethysmography (PPG) as the standard...[but] PPG results are, themselves, not reliable enough...the few independent researchers who have published their data have argued that the reliability and validity of the first phase of the AASI is not yet established...Dr. Abel’s recently published study on the second phase of the AASI, claiming to discriminate between non-child molesters and molesters who deny molesting children, has notable drawbacks...The probability score is generated by comparing the current subject to a pre-determined 'sex-offender profile,' in direct opposition to ethical and practice standards...It can be argued that the AASI has gained acceptance because many treatment professionals have purchased it—more than 1000 according to the Abel web site...Conversely, it can be argued that the scientific community has not accepted it because scientists have not been allowed to access and review the data, much of which is closely-held, and therefore remain skeptical.7


Sometimes polygraphs—that is, lie detectors—are used to force the youth tell the truth about his or her sexual feelings and activity. (Polygraphs are also used to enforce compliance with treatment requirements.) A 1996 survey found that 20% of juvenile sex offender programs for children ages 12 and up used them. It did not indicate whether any programs for younger children did so.3 Like the AASI, polygraphs are not accepted by scientists for use on adults, let alone juveniles.

  • The use of lie detectors has little basis in science...Overall, we give lie detector tests a failing grade.6
    --Statistical Assessment Service, George Mason University
  • Although controversial, the use of polygraph tests in treatment programs for juveniles who have been sexually abusive is increasing...Research regarding the reliability and validity of the polygraph for assessing juvenile sex offenders is very limited. Some researchers have seriously questioned the validity of the polygraph...Both false positives and false negatives occur, and the emotional impact of polygraph administration on juveniles and the resulting effects on the therapeutic process remain unknown.8
    U.S. Office of Juvenile Justice

  • To date, there is little research on the polygraph’s reliability and validity in the evaluation of sexually abusive youth.5
    Center for Sex Offender Management


The penile plethysmograph (PPG) is a device that was used in the early 1900s to diagnose homosexuality. It is still used today to measure sexual deviance among males. It is connected to a male's penis to directly measure his sexual arousal while he is exposed to sexually arousing photographs or audiotapes involving adults, adolescents, and children. This is referred to as "phollometric assessment."

The purpose of the phallometric assessment is to provide objective data regarding sexual arousal. Additionally, it can assist in monitoring changes in sexual arousal patterns which have been modified by treatment. If methods such as the use of Depo-Provera or Depo-Lupron, masturbatory satiation or olfactory conditioning are employed as an adjunct to treatment, then the multidisciplinary team shall use plethysmography to measure the efficacy of these interventions...For individuals under the age of 14, or for those who may not have attained the maturational level associated with puberty, clinicians should seek interdisciplinary or institutional review of the physiological procedures.

Placement of the gauge should be at midshaft of the penis. Recording of full penile tumescence should be obtained whenever possible. The examiner should ensure that sufficient arousal has been recorded to accurately interpret data. When data is to be interpreted as a percentage of full erection, it is important to request the client to achieve full erection.

The examiner will have available a range of sexual stimulus material depicting various Tanner Stages of development for both males and females, including culturally diverse subject material. Stimulus materials should also be available to differentiate between consenting, coercive, forcible, sadistic and aggressive themes with both adults and children.

A survey conducted in 2000 found that 13% of programs for juvenile offenders ages 12 or over and 5% of programs for younger children used the plethysmograph.4 Although the authors of the survey believe the 5% figure was an error, there have been stories of children as young as 10 years old being tested with the device. Click here to see a TV news report about its use on children ages 12 and over in New York in 1993.

The validity of the plethysmograph has not been established when used on adults, let alone children. Like other tests, it has never been validated by testing on a representative sample of American children to determine normal responses.

Research has not been conducted to assess the arousal patterns of juveniles in the general population, therefore, there is no normative data...Although there is an absence of empirically based data, clinical impressions indicate that a higher percentage of developmentally delayed clients tend to respond with uniformly high arousal...In spite of these limitations, phallometric assessments can offer valuable information to those service providers working with the developmentally delayed population.
--Colorado Standards for the Treatment of Juvenile Sex Offenders

...the device has been the subject of many scientific studies and the results have been mixed, to put it kindly. The reliability and utility of the device have been argued in court and penile plethysmographic evidence has been declared inadmissible because of its 'questionable reliability.'...Therapists use the PPG to help them devise treatment programs and to measure the success of their treatment. All this is done without any concern, apparently, that there is no compelling evidence that sexual arousal or non-arousal from pictures or sounds significantly correlates with criminal deviant behavior...One glaring problem with the use of the PPG is the lack of standardized materials to use as stimuli for subjects, a factor which clearly biases the data. Therapists vary greatly in the kind of materials they use to arouse subjects. Some materials are rather tame, e.g., nude adults, children in underwear or bathing suits. Others use hardcore pornography, including depictions of rape and pedophilia. Furthermore, there is no standard of "deviancy" for arousal. Worse, if therapists can define certain arousal as deviant, they can then suggest treatments for the deviancy as well as having the power to declare when the 'deviant' is 'cured.' Convicted sex-offenders are in no position to protest either declarations that they have 'deviant arousals' or treatments forced upon them in the name of curing them of the 'disease' of 'deviant arousal.' More objectionable than the questionable scientific validity of the device, however, are the moral and legal questions its use raises. Some of the materials would probably be illegal on the open market because they constitute child pornography.2
--Skeptic's Dictionary

Also see this article about the lack of scientific validity of the plethysmograph. If plethysmographs are unreliable when used with adults, they are even more so when used with children and teenagers.

  • Research suggests that issues of client age and denial compromise the validity of plethysmographic assessment of juveniles. Younger clients appear to produce less reliable patterns of responding.5
    --Center for Sex Offender Management

  • The use of penile plethysmography with juveniles is particularly lacking in scientific support. Dr. Judith Becker in her testimony before this committee and before the Board of Psychologist Examiners candidly acknowledged that there is no normative data regarding the plethysmograph with juveniles...As this committee is well-aware, during the plethysmograph testing children are subjected to nude slides of men, women, and children, including photographs depicting bondage...children who responded to the "nude adolescent in bondage" photograph were informed of their responsiveness to these photographs -- in essence being told by an adult in authority that they exhibited a deviant sexual interest in bondage. Without data on the responsiveness of "normal children," these children were nonetheless labeled as deviant...9
    --Attorney Lois Yankowski

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Understanding the Issue

When experts are wrong
Casualties of war
   Lack of knowledge
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   Humiliation as therapy
   Arousal reconditioning
   Dangerous drugs
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Deja vu