Psychophysiological Assessmentalpha-assessment.jpg

While assessing and treating sex offenders is not an exact science, it is necessary to provide services which are as comprehensive and competent as possible. Psychophysiological assessment can add a significant dimension to sex offender assessment, to treatment progress measurement and to treatment objectives refinement.  Knowing an offender’s arousal profile can raise questions about the offender's truthfulness and can help counter denial.   It can also help in developing reoffense prevention plans.
Alpha’s laboratory can perform assessments for other treatment providers lacking this equipment.  Examinations can be scheduled for weekdays, evenings and Saturdays.
Psychophysiological Assessment tools available through
Alpha include:

  • Plethysmograph (PPG)
  • Abel Assessment for Sexual Interest™
  • Psychophysiological Detection of Deception (PDD)



Plethysmography is a way of measuring erectile response to various sexual stimuli. When used as a part of a psychophysiological assessment, it can help provide a profile of a client’s sexual interests or preferences.
In doing an assessment, the subject and the operator are in separate rooms. The subject places an expandable strain gauge on his penis and is shown sexually explicit stimuli. These stimuli are in the form of slides, videotapes, and audiotapes. The stimuli are designed to vary across age and gender categories as well as to types of aggression. Comparisons are drawn regarding the relative strength or intensity of arousal to different age ranges, gender, and aggression. The individual’s subjective opinion of how aroused he is to the stimuli is also obtained and compared to the measured arousal.
The plethysmograph has been shown to measure sexual preferences quite accurately for pedophiles, rapists, fetishists, and persons of differing sexual orientations. It is an “objective” physiological measure which has criterion-related validity. Of course, like any information, the results must be interpreted carefully and only applied within the context of the data from all other sources. In no case should the results be used without collateral information or as the sole determinant of decision-making.
The plethysmograph is not a “lie detector” and cannot be used to prove that a client acted out a particular behavior nor can the results be used to predict the probability of future offending. It is, however, a tool to help clarify an individual's sexual arousal patterns and, as such, can be a vital tool in the overall assessment and treatment of sex offenders.


 The Abel Assessment for Sexual Interest™

The Abel Assessment  for Sexual Interest™ is an alternative technique for evaluating the deviant sexual interest of sex offenders.  It is noninvasive, does not require stimuli depicting nudity and always yields some response (i.e., there are no "non-responders" or "flat-liners" as one occasionally observes with the PPG).  The Abel Assessment has two components, a questionnaire that asks about sexual thoughts, fantasies, and behavior, and a computerized assessment of self-reported arousal to slides depicting images of young boys and girls, male and female teenagers and adult men and women.  The Abel Assessment may be administered alone or as a complement to the PPG.  It can be used to evaluate men, women, boys and girls 12 years of age and older.  As with the  plethysmograph, the results should not be used without collateral information and should be part of a multi-faceted evaluation/assessment battery.


Psychophysiological Detection of Deception Exams

Psychophysiological Detection of Deception (PDD) Examinations combine the assessment methods of a polygraph and voice stress analysis to aid in determining if clients are being candid in their disclosures. The PDD exam is a tool available in the assessment and treatment of clients at Alpha and is used to verify full disclosure about a client's sexual offense and sexual history.  In addition, it is used to monitor compliance with the rules of probation and Alpha's treatment programs.  Arrangements can be made for PDD examinations for individuals who are not active clients of Alpha’s treatment programs.