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The possibilities of the participants faking the outcome of a phallometry assessment are well recognized. The main possibilities are as follows:
Motivations for such faking vary widely.
One obvious reason for faking disinterest is its utility for the offender's disposal, since it may support his claims that he does not need therapy or even that he is innocent. One should not forget, either, that many people undergoing therapy are highly hopeful of its success, so faking may also serve to demonstrate that their progress in therapy has been good: if the offender is no longer aroused by pictures of naked children then surely this is progress? After all, therapy is partially designed to help offenders to suppress deviant thoughts.
Similar motives may underlie faking interest: if the offender can show that he is aroused by adult men or women, then this is a contra-indicator of his paedophilia or evidence of the success of the treatment he has received. In other words, a faking pattern may emphasize apparent interest in adults and minimize apparent interest in children.
Furthermore, an offender who is keen to demonstrate that he is helpful and cooperative may fake arousal in keeping with his pattern of offending.
Overall, faking may take into account the reasons for the assessment, the benefits available to the offender as a result of demonstrating a particular pattern in the assessment, the beliefs of the offender about the measurement process, how it is seen by those responsible for his disposal through the system and the nature of the relationship between the offender and the staff dealing with him.
Research on faking has largely confirmed that the outcomes of assessment may be influenced by the use of particular instructions.
For example, Abel, Blanchard and Harlow (1981) gave one of two alternative instructions to groups of rapists, homosexuals, exhibitionists, paedophiles and others. Each was instructed either to "let himself become sexually aroused" or to "voluntarily suppress his erection to that stimulus by mental means" (p. 27). The suppression instruction worked well enough, although not completely successfully.
Similarly, Quinsey and Carrigan (1978) studied a community sample of (presumably non-deviant) men. They were asked, for a reward, to fake a sexual preference for slides of 5-11-year-old girls in various stages of undress although they had previously demonstrated a socially acceptable preference for young female adults. Four out of five of these men managed to fake the paedophile pattern. Quinsey and Carrigan suggest that paedophiles may not have this level of control over their arousal.
Using a procedure in which lights signalled an erection, it was found that only 30% could achieve control over their arousal. Supplementing this procedure with a mild electric shock as well as the signal light only increased the percentage who had control to 50%.
Perhaps more important is the study by Hall, Proctor and Nelson (1988), which demonstrated that overwhelmingly men were able to suppress their arousal to previously arousing material when given instruction in this. Four out of five completely eliminated signs of arousal; less than 4% were unable to reduce their levels of arousal to the previously arousing material.
While it is possible to reduce faking, most research using phallometry has not controlled for faking. Some clinicians and researchers scrutinize their pen records for what they consider to be tell-tale signs of crude faking, but this may only deal with faking's tip-of-the- iceberg.
Studies of faking prevention have largely tried to ensure that the participant engages with the erotic material presented and does not use masking fantasy or simply ignore the materials.
For example, ILaws and Rubin (1969) used an irregularly flashing light during a 10-minute erotic film; participants had to signal when they detected it. In this way, hopefully, concentration on the film in question would be enhanced. Nevertheless, participants were still able to inhibit erections to the film. Some of them created competing mental tasks such as doing sums to help them. Interestingly, participants found it much more difficult to maintain an erection in the absence of filmed erotica than to inhibit erections to erotica.
Henson and Rubin (1971) upped the difficulty of the task by requiring participants to describe the contents of the film. Even in these circumstances, when instructed to do so, some of the men were able to inhibit their
erections. Possibly, describing a film's contents is so distracting that
In an attempt to overcome the faking problem, Quinsey and Chaplin (1988) recruited a sample of men from the local community through newspaper advertising. The recruits admitted to no sexual offences. A mixture of stories were used, involving non-sexual interactions between male and female, consenting sex, rape stories involving brutal, physically violent forced sex and violent stories including mugging but with no sexual content.
Participants received (at different times)
Three-quarters of the participants in the research demonstrated a "perfect" pattern. In other words, they behaved in exactly the same way under the instructions to fake if they had the button pressing task to do as they did without instructions to fake. When just asked to fake without the additional task, faking was successful. In other words, the button pressing activity largely prevented faking. All of the participants said that it was difficult to create their own fantasies when required to monitor for violent and sexual content. Nevertheless, a few of them succeeded: one claimed that he jammed his finger into a protruding nail in the apparatus in order to turn himself off, another was a pilot who claimed that he was trained to do two things at once.
Thus, a high percentage of men are capable of faking the outcomes of a phallometric test, although this is most clearly and decisively shown for the suppression of sexual arousal. Furthermore, it is possible to complicate the task sufficiently to prevent the commonest
forms of faking in most men.
Nevertheless, practitioners cannot eliminate the small minority of men who can fake irrespective of the procedures employed. The fact that when encouraged to do so many men are capable of faking does not mean that the majority of men actually do fake during assessment; some may, but we do not know how many:
Quinsey and Chaplin (1988) describe how some of the offenders at their institution had been instructed by their peers on how to fake on the phallometric test! Because of this, research on phallometry there is largely limited to new clients at the institution who might not have been so influenced. Clearly, phallometry is not a simple, infallible measuring procedure but something involving complex social contingencies about which only limited knowledge and speculation are available. The question is the degree of faith one can have in available findings about phallometric differences between offender types.
Phallometry is not a "sexual lie detector" (Farrall and Card, 1988) because it is not sufficiently precise to divulge whether a man has offended or is likely to do so. It would be virtually useless as a community screening device to search for likely offenders. There would be too many false identifications to make it worthwhile and too great a possibility of faking.
Nevertheless, it does have uses: it gives strong pointers as to the ages and sexes that are arousing in men who may have difficulties in admitting their socially unacceptable sexual feelings. In such cases, where the phallometric data is at variance with what is disclosed, the additional information can be helpful in taking the therapy forward if used sensitively.