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In search if an etiological model of pedophilia

Kurt Freund*


Epidemiological and "quasi-developmental" research into pedophilia is reviewed. Both types of inquiry were made possible only by the use of the phallometric method which assesses erotic sex and age preferences by continuous recording of penile volume changes. This method by itself, however, has shortcomings, which are pointed out. It appears likely that pedophilia research may acquire a firmer basis by further development of brain imaging.

Key words

Pedophilia; Phallometry; Brain Imaging.


Pedophilia belongs among the paraphilias, or pathological erotic preferences. These can be crudely divided into two broader categories: paraphilic "target" preferences and paraphilic activity preferences. In the former, the targets of erotic or sexual cognition are not primarily (other) physically mature persons, and the paraphilic activity preferences are characteristically highly atypical for sexually normal persons. Pedophilia seems to be primarily a target preference, however, it has been more recently demonstrated that there are regular connections between paraphilic activity preferences and target preferences (Freund, 1994).

Identification of the Disorder

The recognition of pedophilia as a specific disorder is attributable to Krafft-Ebing (1886); however, some authors continue to use this term to denote a variety of different clinical pictures. This was pointed out by Ames and Houston (1990) and Araji and Finkelhor (1985). The revised third edition of the Diagnostic and Statistical Manual of Mental Disorders (D.S.M. III-R, 1987) lists the essential feature of pedophilia as "recurrent, intense sexual urges and sexually arousing fantasies of at least six months’ duration, involving sexual activity with a pre-pubescent child" (p. 284). For our purposes the period of childhood is defined as ending at age 12, an age limit adopted from Gebhard et al. (1965).

Diagnosis and Diagnostic Research

Fantasies focusing on children, as mentioned in D.S.M. III-R (1987), do constitute one of the foremost characteristics of pedophilia, however, relying on self-reports of fantasies is of little diagnostic value since pedophiles rarely admit their true erotic fantasies. Because pedophilia is very rare in females (Gebhard et al., 1965), all diagnostic research could be focused on males only. Therefore, instead of relying on reports of such fantasies, we have been diagnosing pedophilia by phallometry, which is a continuous recording of penile volume changes during the presentation of pictures of nude female and male children and adults. According to their phallometric responses, pedophiles are those who erotically prefer children to adults. This is also the case when the stimuli are verbal and depict sexual interaction between the tested individual and a child versus such sexual interaction with an adult. Phallometrically, about 80% of sex offenders who victimized two or more children (unrelated to them) are diagnosed as pedophiles, whereas only about 5% of sex offenders against women are mis-diagnosed as pedophiles (Freund and Watson, 1991). It must pointed out, however, this data was collected from labs using volumetric phallometry, a computer diagnosis which included signals of faking, and strong stimuli; hence our results may be more reliable than those of less equipped labs.

Therapy and Therapy-Research

There are currently three therapeutic approaches. The first is psychotherapy, derived from experiments with animals (Pavlovian and Skinnerian learning — Laws and Marshall, 1990; Pithers, 1990). The second focuses on serotonergic medication (see the critical review by Federoff, 1993). Lastly, the third is sex drive reducing medication or sex drive reduction by testicular enucleation (Berlin and Meinecke, 1981; Freund, 1980; Hucker, 1985, 1992; Wille and Beier, 1989).

The opportunistic offenders will probably profit from any kind of psychotherapy or counseling and from punishment itself also. However, although the phallometric method is fraught with insufficiencies, it still reliably divides therapeutic candidates into true pedophiles and opportunistic sex offenders against children. Once this division has been made, the assessment of therapeutic effect could be carried out separately for each of these two offender groups. For many reasons, the long-term use of the various medications is not feasible and testicular enucleation as a therapy for the paraphilias is socially unacceptable in most western countries.

Epidemiological Research

The following was an epidemiological study which also has etiological implications. Epidemiological studies can currently be conducted only with individuals accused of offenses against children, and not with pedophiles proper. Only in rare cases are such sex offenders against children individually assessed and differentiated into true pedophiles and opportunistic offenders. At present, similar serious limitations hamper all systematic research on pedophilia.

Two earlier studies on paraphilias (Gebhard et al., 1965; Mohr et al., 1964) reported that the proportion of sex offenders against female children to that of sex offenders against male children was about 2:1. In our own endeavors (Freund et al., 1984; 1987)) we also found a similar proportion. A literature search (Cameron, 1985) that involved 17 additional studies on sex offenders against children, listed the ratio of victimized female to male children in the majority of cases also as approximately 2:1. This differs substantially from the ratio of gynephiles (men who erotically prefer physically mature females) vs. androphiles (who erotically prefer adult members of their own sex) which is minimally 20:1 (Gebhard, 1972; Hirschfeld, 1920; Kinsey et al., 1948; Whitam, 1983).

The discrepancy between the proportions of heterosexual and homosexual offenders against children, on the one hand, and of gynephiles and androphiles on the other, was unexpectedly large. However, Abel et al. (1987; 1988) reported that sexual offenders against male children have many more victims than such offenders against female children. According to the data of these authors, the mean number of victims of offenders against female children was 19.8, while that of such offenders against male children was 150.2. Abel et al. (1987,1988) pointed out that the much larger number of victims of offenders against male children increases the risk of these offenders’ being caught. However, the rate of increase for this risk and the number of victims remains unknown. Mohr et al. (1964) also reported a higher recidivism rate in sex offenders against male children, as contrasted with sex offenders against female children. Fitch (1962) concurred; whereas Gebhard et al. (1965) reported only a marginal difference.

The tendency of the offenders against male children to have a greater number of victims suggests that this group may contain a larger proportion of true pedophiles than the group of offenders against female children. This conjecture concurs with the results of two earlier studies. One of these studies, (Freund et al., 1987), compared sex offenders against female minors and sex offenders against male minors ("incest" offenders excluded). Among the offenders against female children there were more individuals who had only one victim rather than two or more victims, whereas among offenders against male children the opposite was true.

Another earlier study calculated the sensitivity of the phallometric method in diagnosing multi-victim offenders against girls, and used the ratio of those diagnosed versus non-diagnosed as pedophiles with single-victim offenders, to arrive at an estimate of the numbers of true pedophiles in this group. A similar operation was carried out using other specified subgroups and analogously with offenders against male children (Freund and Watson, 1991).

Using these estimates, we converted the "raw" proportions of specified subgroups within the group of sex offenders against female children and within the group of sex offenders against male children into estimates of the proportions of "true" heterosexual and homosexual pedophiles. The result of this conversion was a ratio of heterosexual versus homosexual pedophiles of 1.44:1. However, the earlier cited finding of Abel et al. (1988) of a mean number of victims 7.6 times larger for offenders against male children than the mean number of victims for offenders against female children also has to be considered. After recalculation of this increased risk of an offender’s being caught, and under the supposition that this risk increases proportionally and linearly with each victim, our estimate of the ratio of the offenders against female children versus offenders against male children was recalculated to approximately 11:1. For a number of reasons, this may be an upper limit or, more likely, quite exaggerated. One reason is that this estimate did not take into account that the low number of victims of offenders against female children, found by Abel and co-workers, must have been strongly influenced by the fact that there were substantially fewer pedophiles among the offenders against female children than there were against male children. The ratio of heterosexual to homosexual pedophiles was, however, still substantially smaller than the ratio of heterosexual versus homosexual males who erotically preferred physically mature persons. The most parsimonious interpretation of this result is that the heterosexual and homosexual types of pedophilia are substantially more closely related to each other than to the heterosexuality or homosexuality of males who erotically prefer physically mature partners. Also, pedophilia has little in common with homosexuality or heterosexuality in males who prefer physically mature partners.

Differences in Self-Reported Masculinity and Femininity

The derived proportion of heterosexual and homosexual pedophiles given above, appears to indicate that there may be differences other than sex-preference between them.

Two earlier studies (Freund and Blanchard, 1987; Freund et al., 1984) demonstrated that Part A of the Gender Identity scale (Freund et al., 1974; 1977) successfully differentiated between androphiles and offenders against male children, but not between offenders against male children and offenders against female children. On the other hand, the 1987 study (quoted above) seems to indicate that Blanchard’s (1983) retrospective Physical Aggressiveness scale differentiated between homosexual and heterosexual pedophiles. However, this study was a comparison of sex offenders against female children and sex offenders against male children, and not of phallometrically diagnosed heterosexual and homosexual pedophiles. It may have been confounded by the differing proportions of true pedophiles among the heterosexual and homosexual offenders. This comparison has to be replicated with phallometrically diagnosed pedophiles before it can be acknowledged as valid.

The Abused Abuser Theory

One of our two solely etiological studies was about the abused abuser theory of pedophilia. The majority of professionals (and particularly of semi-professionals) working in the area of pedophilia believes that this propensity is due primarily, if not exclusively, to an individual’s developmental experience rather than to a pre-experiential innate or physiologically acquired condition. The prevailing version of this conjecture supposes that pedophilia, or at least an individual’s proneness to sexually offend in adulthood, is due to having been sexually abused in childhood by an adult. The main problem with this conjecture is its dependence on self-reports about childhood sexual abuse among accused or charged sex offenders against children. It has been shown that a large proportion of such offenders fabricate childhood sexual abuse as an excuse or form of exoneration for their behavior (Hindman, 1988).

Two of our earlier publications on this topic (Freund et al., 1990; Freund and Kuban, 1994), using various groups of males, investigated the connection between the subject’s retrospective self-reports of having been sexually abused in childhood, his erotically preferred age bracket, and type of offense. The earlier of these two studies was only preliminary and will not be discussed in detail. The second study included 83 pedophilic sex offenders against female children, 52 sex offenders against female children who, however, erotically preferred adult women, 34 sex offenders against adult women and 134 gynephilic volunteer controls. The differentiation between pedophilic and non-pedophilic sex offenders against children was determined by means of phallometry.

The main statistical procedure used in this study was logistic regression. The result verified two significant predictors: erotic age preference (pedophilia versus an erotic preference for adults), and sex offender status. However, this latter predictor, was actually a combination of two predictors, namely, status of a sex offender against children and status of a sex offender against adult females. It derived its predictive potential mainly from the status of being a sex offender against children. The described result seemed to support the abused abuser theory. We must, however, not forget that this study could only test the validity of the clinical observation of a higher frequency of self-reports of (heterosexual) pedophiles having been sexually abused in childhood and not whether the pedophiles were really sexually abused.

Finkelhor (1984) pointed out the presence of a large "error" of the abused abuser theory. The present study specified this error: Only about one third of the pedophiles indicated sexual abuse in their childhood. Under these conditions it would be a mistake to conclude that an association between pedophilia and a self-report indicating sexual abuse in childhood, settles the problem of causation of pedophilia. Further etiological possibilities will have to be investigated.

Because of the demonstrated possibility of a physiological disposition towards pedophilia, the following discusses research into the physiological aspects, which has been and is largely omitted, in particular by learning theorists and "anthropological" ethologists (Feierman, 1990). First, however, a reminder to avoid misunderstandings. The popular division of etiologies into "innate" and learned (experiential) is misleading and should instead be replaced by examining the nature of the involvement of each component. However, the difference between females and males in regard to pedophilia (mentioned earlier) makes it very likely that there is a strong physiological factor.

Retrospective Self-reports about Erotic Curiosity

The "Abused Abuser" study indicated that a majority of pedophilic sex offenders did not report seduction in childhood. We tried to re-investigate this incongruity. This additional research was an attempt to specify when the first difference appeared between male children and pubescents who as adults would prefer children and those who would prefer physically mature persons. We approached this problem also by means of a self-report study (Freund and Kuban, 1993).

This study investigated three aspects of the development of erotic sex and age preferences in males: (a) whether the supposition of a strong innate factor or an early postnatally acquired factor (most likely physiological) in the development of pedophilia can be supported by childhood memories, (b) whether the experience of an almost abrupt decrease in the erotic appeal of children in boys who later become gynephilic, can be supported by the retrospective self-reports of a large group, (c) whether the establishment of erotic sex preference precedes the establishment of erotic age preference.

This study made two initial suppositions: (a) that curiosity to see persons in the nude during childhood can be viewed as an indicator of developing erotic interest, and (b) that the retrospective self-reports used in the study reflected reality sufficiently and could be employed in probing the development of erotic curiosity in childhood. The subjects of the study were phallometrically diagnosed pedophiles who admitted to having sexual fantasies about children or pubescents, and control volunteers. The inquiry consisted of the following eight questions incorporated in the Sexual Preferences Scheme (EPES, Freund, 1965, unpublished): 1 Prior to age 7 were you curious to see female children your age in the nude? 2 Prior to age 7 were you curious to see female grown ups in the nude? 3 Between ages 7 and 11 were you curious to see female children your age in the nude? 4 Between ages 7 and 11 were you curious to see female grown ups in the nude? The four additional EPES questions (5 to 8) had the same wording, with the difference being that the word "female" was replaced by "male".

The retrospective reports about childhood curiosity differed substantially from the earlier described retrospective self-reports concerning sexual abuse in childhood, which, when answered in the positive, could to some degree exonerate the offender and fault the earlier abuser. None of the possible answers to the questions asked in this study was as obviously endowed with the potential to bias an interviewer favorably towards the offender, and if occurring, the most likely distortion resulting from offender bias would be a diminution of the true number of pedophiles claiming a childhood curiosity to see nude children.

The results of the study suggested that a greater proportion of pedophiles reported a childhood curiosity to see nude children and not adults than did the other groups. This suggests that, in a substantial proportion of pedophiles (possibly in all of them), this paraphilia may well have been present from early childhood or infancy or may have developed from an innate disposition. The study also suggested that throughout the developmental process of erotic sex and age preferences in males, the establishment of erotic sex preference precedes that of erotic age preference, and that the establishment of erotic sex preference in gynephiles and heterosexual pedophiles occurs earlier than it does in androphiles and homosexual pedophiles. Furthermore, according to the memories of volunteer gynephiles, the almost abrupt decrease of the impact of the erotically non-preferred age bracket, in this case of female children, occurred around the onset of puberty.

The two initial suppositions, on which this study was based, were a, that curiosity to see persons in the nude during childhood can be viewed as an indicator of developing erotic interest, and b, that the retrospective self-reports used in the study, reflected reality sufficiently and could be employed in probing the development of erotic curiosity in childhood, were proven adequate. The adequacy of our first supposition was made plausible by the observed increase of curiosity to see persons in the nude during the latter years of childhood, as contrasted with the period prior to age 7. The second supposition was made plausible by the high proportion of individuals who reported such a curiosity in regard to persons of the sex and age they preferred in adulthood.

A study by Gaffney et al., (1984) appears to suggest that this physiological factor is genetic. This study compared relevant information about the prevalence of the various kinds of paraphilias in first degree relatives of 33 pedophiles (defined according to DSM - III) hospitalized at Johns Hopkins for therapy, and of 33 patients hospitalized for depression. There was a greater prevalence of paraphilics in the families of the pedophilic probands and all were characterized by the probands as pedophiles and as males. The various paraphilics in the control group of depressives indicated a variety of paraphilias in their families. Furthermore, in contrast to the pedophilic sample, the morbidity risk in regard to paraphilias (calculated by means of a shortened Weinberg method) among the relatives of the paraphilics in the control sample was minimal. Our clinical experience does not correspond to these findings but our questioning of patients in this regard was quite superficial.

There may exist a genetic form of pedophilia without this disturbance being genetically transmitted in most cases. A patient whose pedophilia may have been due to genetic transmission was described in an earlier study (Freund and Blanchard, 1993, p. 560/561). He had four brothers, one of them, his twin, is most likely also pedophilic (see original study). Among the three older brothers, two started approaching him sexually when he was 10 years old. I saw both in adulthood when they were charged for pedophilic offenses.

Another type of findings, relevant to a possible physiological disposition towards pedophilia was reported by Langevin and his group. These investigators reported crude structural anomalies of the brain of pedophiles, detected by CAT (computer assisted tomography, — Langevin et al., 1985, 1988; Hucker et al., 1988, 1992; Wright et al., 1990). These studies are still in their initial phase.

Options for Further Research

The reviewed pedophilia studies were epidemiological and "quasi-developmental". Both types involved phallometry.

Quasi-developmental research uses retrospective self-reports about childhood experiences, behavior, or ideation, and may reveal promising directions for later true developmental research. The main shortcoming of our epidemiological pedophilia research is the lack of reliable methods of transforming assessments of large numbers of sex offenders against children into such outcomes regarding pedophiles.

The transformations used in the present epidemiological study compared the ratios of heterosexual and homosexual pedophiles. However, the number of victims of homosexual sex offenders against children appears exceptional; the increase of the risk of being caught, with the increasing number of victims, was arbitrary, and intentionally set to be rather too high than too low. This kind of research can be improved by utilizing various combinations of a number of types of subject selections. The phallometric assessments involved in both types of research need improvement. In particular, they should specify offender groups which are currently lumped together (e.g. homosexual pedophiles and hebephiles).

However, even such improved research in pedophilia can not be expected to render substantially more certain results than individual clinical observation. It also is to be expected that a majority of such research efforts will turn out to be irrelevant. Would it not be better to devote the manpower and funds available for research to more promising ("less risky") endeavors. Why should the practical urgency of the problem of pedophilia take precedence over the lack of scientific feasibility in this area?

On the other hand, for the systematic observer, this may not be a sufficient reason to leave her or his own clinical impressions unexplored, or to cease testing the clinical impressions of others. This pertains only if the methods used in such explorations are of sufficient clarity and can be formulated unambiguously enough to make replication possible by alternative methods.

The present writer’s impression is that the kind of research most promising in this area, and possibly the most feasible in the not too remote future would examine anomalies in brain structure. However, the possibilities of finding connections between pedophilia and insufficiencies in neural structures provided by CAT (computer assisted tomography) are very limited, and PET (positron emission tomography) can not be used for repeated assessments within a relatively short time period. MRI (magnetic resonance imaging) does have these problems to a much lesser degree, however, the spatial resolution achieved may still not be sufficient. The most recent development, the MSI (magnetic source imaging) however, which is a combination of Supermagnet MRI with EEG scanning (Gallen et al., 1993), appears promising in resolving this difficulty and may develop enough in the not too distant future sufficiently, to make possible the localization of brain structures relevant to paraphilia research.


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