part0027

Ponseti et al. (2012) found significant differences between 24 persons with pedophilia from the Dunkelfeld Project, all of whom admitted their sexual interest in prepubescent children, and 32 teleiophilic individuals using sexual stimuli depicting nude men, women, boys, or girls, including genital close-ups. Both the pedophilic and teleiophilic groups were split approximately equally into those interested in males or in females. The study found significant differences, particularly in brain areas involved in the processing of sexual stimuli, including the caudate nucleus, insula, thalamus, amygdala, fusiform gyrus, cingulate cortex, temporal cortex, occipital cortex, and cerebellum. These areas in turn are functionally connected and related to structural differences found in previous neuroimaging studies, suggesting an emerging understanding of the functional and structural network differences underlying pedophilia (Cantor et al., 2015; Poeppl et al., 2015). Using a classification algorithm based on these differences, Ponseti et al. reported 100% specificity and 92% sensitivity, which is much higher than what is found for pedophilia measures (see Chapter 2 ).

More recently, Ponseti et al. (2016) also reported impressively high classification accuracy—91% specificity and 95% sensitivity—using stimuli depicting faces varying in gender and age category only. They recruited 24 pedophilic and 36 teleiophilic men; the pedophilic men were approximately evenly split in their attraction to boys or girls; 11 were help-seeking persons with pedophilia from the Dunkelfeld Project, and thus mostly unknown to the criminal justice system, whereas 10 of the remaining 13 men had been previously convicted of sexual offenses (mostly child pornography offenses) and were being seen in an outpatient clinic. I bring this detail up because this sample partially addresses the reliance on officially identified offenders in past work. On the other hand, the teleiophilic individuals were nonoffending controls and thus some of the differences might be explained by criminal status; results were not presented separately for the Dunkelfeld versus criminal subsample of pedophilic men.

A great deal of clinical and public speculation has considered whether childhood sexual abuse is related to the etiology of pedophilia (e.g., Garland & Dougher, 1990; Hanson & Slater, 1988). As noted in the previous chapter , evidence is mixed regarding a link between childhood sexual abuse and sexual offending against children, with a significant association in cross-sectional studies but a weak or nonspecific association in longitudinal studies. A potential moderator for the strength of the abuse–offending association is pedophilia or a predisposition to pedophilia, where the abused–abuser link exists among pedophilic individuals but not among nonpedophilic individuals. In Jespersen, Lalumière, and Seto (2009), we found that sex offenders against children (some of them likely to have pedophilia) were more likely to have been sexually abused than offenders against adults, whereas the reverse pattern was found for physical abuse history. In adolescents, sexual abuse history is also correlated with sexual offense characteristics known to be correlated with pedophilia, including having boy victims (Becker, Kaplan, & Tenke, 1992; Kaufman, Hilliker, & Daleiden, 1996; Worling, 1995; but see Aylwin, Studer, Reddon, & Clelland, 2003), multiple child victims (Becker & Stein, 1991; Renshaw, 1994), and younger victims (Kaufman et al., 1996).

More indirect evidence for an association between childhood sexual abuse and pedophilia comes from Lee, Jackson, Pattison, and Ward (2002), who classified 64 adult sex offenders into pedophilia, biastophilia (coercive sex), exhibitionism, or multiple paraphilia groups. Childhood emotional abuse and childhood behavior problems were common across the paraphilia subgroups and were more prevalent in all the paraphilia groups compared with 33 nonviolent offenders. Childhood sexual abuse was specifically associated with pedophilia because it did not distinguish biastophilic or exhibitionistic individuals from the others. Two studies found that adult sex offenders who reported being sexually abused as children were more likely to admit being sexually aroused by children themselves (Fedoroff & Pinkus, 1996; Freund & Kuban, 1994). Several studies have found that adolescent sex offenders who were sexually abused showed relatively greater sexual arousal to children than to adults (Becker, Hunter, Stein, & Kaplan, 1989; Becker et al., 1992; Hunter & Becker, 1994). I was not able to find comparable phallometric studies conducted with adults who have sexually offended, except for Lussier, Beauregard, Proulx, and Nicole (2005), who found that childhood sexual abuse by an extrafamilial perpetrator was related to sexual arousal to children, assessed phallometrically. Lussier et al. also found that higher scores on a sexualization factor—comprising paraphilic sexual fantasies, sexual offending history, and sex drive as reflected in masturbation and conventional sexual experiences—mediated an association between sexual abuse by an extrafamilial perpetrator and sexual responses to stimuli depicting sexual violence toward children.

The sexual abuse link is further complicated because child pornography offenders are less likely to be sexually abused than contact sex offenders, yet they are more likely to have pedophilia or hebephilia (Babchishin et al., 2015). It may be the case that sexual abuse history is tied to expressing pedophilia in the form of contact sexual offending, but not in the form of child pornography offending. Otherwise, one would expect child pornography offenders or self-identified individuals with pedophilia to have more extensive childhood sexual abuse histories.

Santtila et al. (2015) found that sexual interest in children under the age of 16—which would encompass pedophilia, hebephilia, and attraction to adolescents that might constitute ephebophilia or normative sexual attractions—was associated with childhood sexual as well as physical abuse. There were too few respondents to focus on sexual interest in only younger children. Sexual interest in children under age 16 was also associated with higher sexual desire, more frequent sexual fantasies, and more frequent masturbation, consistent with the idea that some pedohebephilia-like attraction (and behavior) is associated with high sex drive or hypersexuality. Klein, Schmidt, Turner, and Briken (2015) also found a positive association between childhood sexual abuse and admission of pedophilia or hebephilia in a community sample of over 8,000 German men, although the base rates were not reported.

Most sexually abused children do not go on to sexually offend, indicating that individual differences in personal vulnerabilities underlie any effects of sexual abuse on pedophilia or sexual offending. For example, many of the sexual offending models described in the previous chapter suggest that individuals with biological vulnerabilities are more susceptible to adverse childhood experiences such as sexual abuse (e.g., Ward & Beech, 2016). The most obvious vulnerability is being male. Most known persons with pedophilia and most offenders against children are male, yet the majority of child sexual abuse victims are girls. Evidence indicates that childhood sexual abuse affects the psychosexual development of girls as well, but in a way that puts the girls themselves at risk, rather than others (e.g., Trickett, Noll, & Putnam, 2011). Salter et al. (2003) found that sexually abused boys who later committed sexual offenses were significantly more likely to also have experienced neglect, lacked parental supervision, or witnessed serious intrafamilial violence.

Some evidence suggests that when sexual abuse takes place is important. Grabell and Knight (2009) found evidence to suggest a critical age window between ages 3 and 7 for an association between childhood sexual abuse and hypersexuality in adolescent sex offenders, where hypersexuality has been identified as a potential factor in adult sex offender research. Sexual abuse that occurred at an older age was less strongly related. It is still possible that sexual abuse at a younger age is relevant; however, a child is less likely to remember the sexual abuse. Research exploring this idea with parent reports, child protection records, and other sources would clarify whether there is a critical time window, and what ages are involved.

Another potential influence is the nature of the sexual abuse in terms of perpetrator–victim relationship, the sexually abusive behavior, and possibly the duration of the abuse (Burton, 2003; Finkelhor, 1979; Hunter, Figueredo, Malamuth, & Becker, 2003; Knight & Prentky, 1993). Burton, Miller, and Shill (2002) found that sexually abused youth were much more likely to later commit sexual offenses if they were sexually abused by both men and women, the perpetrator used violence, the abuse took place over several years, and the abuse included penetrative acts. Salter et al. (2003) found that having a female perpetrator was associated with later sexual offending among sexually abused boys, which jibes with the self-report data suggesting a higher proportion of female perpetrators of child sexual abuse than official crime statistics would indicate.

Nunes, Hermann, Malcom, and Lavoie (2013) found that among 462 sex offenders, those who had been sexually abused before the age of 16 had younger victims and more evidence of pedophilia, as reflected in sexual victim characteristics as captured by the Screening Scale for Pedophilic Interests (SSPI; Seto & Lalumière, 2001) than those who had not been sexually abused. This was based both on self-report and on officially documented childhood sexual abuse. Moreover, offenders who had a male perpetrator of their childhood sexual abuse had more evidence of pedophilia on the SSPI than those who had a female perpetrator.

Given this converging evidence of an abuse–perpetration link, I discuss possible mechanisms next, focusing on learning explanations. Burton (2003) suggested that learning helped explain the link between childhood sexual abuse and later sexual offending against children, either through imitation of the perpetrator’s behavior, conditioning because of pairing any sexual stimulation caused by the sexual abuse with the types of acts that took place, or by shifting attitudes and beliefs about adult–child sex. In support of these ideas, Burton (2003) reported that adolescent sex offenders who had been sexually abused tended to perpetrate the same kinds of abusive acts they had themselves experienced. Similarly, D. K. Hall, Mathews, and Pearce (1998) found that children who reported becoming sexually aroused during their sexual abuse experiences were more likely to engage in problematic sexual behavior involving others (e.g., unwanted touching). It is interesting to note that D. K. Hall et al.’s sample included both boys and girls between the ages of 3 and 7, which can be compared with the same critical age window suggested by Grabell and Knight (2009). Other factors that distinguished sexually abused children who acted out from those who did not was whether the child was required to actively be involved.

Other writers have suggested that masturbatory conditioning may play a role in the etiology of pedophilia (e.g., Laws & Marshall, 1990; McGuire, Carlisle, & Young, 1964). Many people have their first sexual experiences with similar aged peers when they are children or young adolescents. Some individuals may pair the physical cues of young persons—such as small body size, androgynous body shape, absence of pubic hair, and absence of secondary sexual characteristics—with the sexual pleasure elicited by these initial experiences, and eventually learn to associate these cues with the powerful reinforcement of masturbation to orgasm, consistent with Toates’s (2009) incentive motivation model. Others have the same initial experiences as children, but they continue to have sexual experiences with similar-aged peers as they grow older and do not develop a conditioned response to prepubescent children. Persons with pedophilia are somehow blocked in making this adjustment, suggesting that learning may affect only individuals who are already predisposed for other reasons or who have unusual early sexual experiences (e.g., sexual interactions with other children with adult involvement, in sexual abuse circumstances.) Thus, conditioning is not a sufficient explanation for the etiology of pedophilia but may play a role in a stress–diathesis model wherein at-risk individuals have unusual early experiences and then undergo conditioning. An analogy can be drawn to other major mental disorders for which both genetic and environmental influences play a role.

The evidence regarding a role for conditioning in the development of pedophilia is sparse. As just noted, D. K. Hall et al. (1998) found that sexually abused children who reported evidence of sexual arousal during the sexual abuse episodes were more likely to engage in problematic sexual behavior. Dennison and Leclerc (2011) found that adolescents who had committed repeat offenses against children were more likely to have been sexually abused than those who had not. Dandescu and Wolfe (2003) found that the frequency of pedophilic sexual fantasies increased after the first sexual offense reported by their sample of 57 sex offenders with child victims. However, two thirds of the men in Dandescu and Wolfe (2003) already reported pedophilic sexual fantasies before the first offense, suggesting conditioning may have strengthened rather than initiated their sexual interest in children (although it is possible that the fantasies that preceded the first offense were reinforced by masturbation to those fantasies). Alanko et al. (2010) found that male Finnish twins who reported early sexual experiences with other children had younger preferred and actual sexual partners as adults and were more likely to report an interest in children or youth under the age of 16. This effect seemed stronger if the cotwin was female, both in terms of a greater likelihood of childhood sexual experiences and younger preferred and actual partners.

Indeed, evidence about the impact of positive conditioning on initiating sexual interest in novel targets or activities is equivocal. Probably the earliest demonstrations were reported by Rachman (1966) and by Rachman and Hodgson (1968), who reported significantly increased sexual arousal to pictures of boots among community volunteers after pairing those pictures with pictures of nude women, but these studies did not have the appropriate control conditions. Lalumière and Quinsey (1998) presented 10 nonoffending men with 11 pairings of a slide of an attractive, partially nude woman with a more intense, highly arousing video depicting heterosexual intercourse; another 10 men were exposed to 11 slide presentations only. This study showed evidence of weak positive conditioning: The men in the paired condition showed a 10% increase in their sexual arousal to the slide, and the men in the unpaired condition showed an 11% decrease in sexual arousal, probably due to habituation. In contrast, Plaud and Martini (1999) found mixed results in a conditioning study of nine male volunteers, whereas Hoffmann, Janssen, and Turner (2004) found a significant positive effect of conditioning on sexual arousal in a total sample of 29 nonoffending men, assigned to different conditions. Not much other experimental work has been conducted on human conditioning of sexual arousal (see Hoffmann, 2012). Pfaus, Erickson, and Talianakis (2013) described clear effects of conditioning on subsequent sexual behavior in an animal model of fetishism involving rats who had sexual rewards paired with or without a jacket.

Besides this literature on the positive conditioning of sexual arousal in nonoffending men and women, one can also look at the paraphilia treatment literature, which has used aversive and other conditioning paradigms for decades now, to reduce sexual response to paraphilic stimuli. In particular, studies have evaluated the impact of aversive conditioning to suppress sexual arousal to stimuli depicting children and masturbatory conditioning to increase sexual arousal to adults. I have already discussed masturbatory conditioning, in which stimulus cues are paired with the reward of masturbation and orgasm. In aversive conditioning, unpleasant stimuli, such as the smell of ammonia salts or mild electric shock, can be paired with repeated presentations of arousing sexual stimuli (e.g., images of children). Over time, the pairing of the sexually arousing stimuli with the noxious stimulus will reduce response. (For older but still current reviews of the efficacy of conditioning approaches for changing paraphilic sexual arousal patterns, see Barbaree, Bogaert, & Seto, 1995; Barbaree & Seto, 1997).

Behavioral conditioning can significantly decrease pedophilic sexual arousal among sex offenders, but it is unclear how long these changes are maintained, what mechanisms are actually responsible for the changes in sexual arousal patterns, and whether the changes reflect an actual shift in sexual preference or the learning of greater voluntary control over sexual arousal (Lalumière & Earls, 1992; Mahoney & Strassberg, 1991). These are all important questions: If changes fade over time, then this suggests the need for “booster” sessions to maintain changes; a better understanding of mechanisms would enable researchers to better hone conditioning techniques; and understanding whether changes reflect changes in preference versus changes in ability to control sexual arousal has implications for the understanding of pedophilia as a sexual orientation for age (Seto, 2012, 2017b).

These different lines of research suggest that conditioning is not sufficient to explain the development of pedophilia, although it may play a role in reinforcing expressions of pedophilia, such as how often someone fantasizes and masturbates to thoughts about sex with children. Experimental efforts to increase sexual arousal to nonpreferred stimuli have produced small effects in the lab (10% after only 11 presentations [Lalumière & Quinsey, 1998] vs. a potential long lifetime of conditioning), and it is unclear how long conditioned sexual responding can be maintained. No empirical evidence indicates that pedophilic men are more likely to have sexual experiences with other children when they were children themselves, although pedophilic offenders may be more likely to experience sexual abuse by much older youth or adults (Jespersen et al., 2009; Seto & Lalumière, 2010). Some persons with pedophilia report an onset of sexual interest in children before any sexual contact with children (Dandescu & Wolfe, 2003; Freund & Kuban, 1993b). A big question that remains to be explored is why the sexual abuse experience results in behavior directed toward children rather than toward adults, given the perpetrators were adults and most conditioning paradigms would suggest any sexual arousal experienced during the abuse is paired with the adult rather than with self.

Whether the mechanism involves learning or not, it is possible that childhood sexual abuse has a pervasive effect on subsequent sexual development, increasing not only the likelihood of sexual offending against children but also other sexual behavior. In their small study of 36 individuals, McElroy et al. (1999) found that paraphilic subjects were more likely to have a sexual abuse history than nonparaphilic subjects. No association was found by Kafka and Hennen (2003) using a larger clinical sample. Knight and Sims-Knight (2003) found that the association between sexual abuse history and sexual offending was mediated by hypersexuality (high sex drive, high levels of fantasy, sexual preoccupation, feelings of compulsivity), such that childhood sexual abuse increased the likelihood of hypersexuality and that in turn increased the risk of sexual offending by adults. On the other hand, this mediation was not demonstrated in two subsequent studies of juvenile sex offenders (Daversa & Knight, 2007; Knight & Sims-Knight, 2004). Cale, Leclerc, and Smallbone (2014) looked at noncriminal sexuality in a sample of 546 incarcerated sex offenders. Childhood sexual abuse was related to an earlier onset of sexual activity, more pornography use, more masturbation, more fantasy, but lower levels of satisfaction and perceived sexual success as an adult.

Sexual abuse may affect psychophysiological development, as some evidence suggests it is associated with a lower age of onset of puberty, perhaps through the results of stress (e.g., cortisol affecting puberty timing; Belsky, Steinberg, & Draper, 1991). Three studies have found that sexually abused adult sex offenders reported an earlier onset of masturbation than other adult offenders, wherein onset of masturbation is related to both puberty onset and hypersexuality (Cale et al., 2014; Cortoni & Marshall, 2001; Smallbone & McCabe, 2003). J. Brown, Cohen, Chen, Smailes, and Johnson (2004) found that men or women who experienced two or more episodes of childhood sexual abuse had an earlier onset of puberty by an average of 2 years.

An alternative explanation for these findings is that earlier maturing children are at greater risk of being sexually abused by nonpedophilic men. Another alternative explanation is that the association is genetically mediated because a substantial proportion of childhood sexual abuse is perpetrated by parents or other family relatives, and that predisposition might be passed on genetically or familially. Analyses of sexually abused children distinguished by relationship to perpetrator support this idea. Burton, Miller, and Shill (2002) found that whether the perpetrator was related to the abuse victim was associated with later sexual offending.

The evidence regarding a genetic predisposition toward sexual offending or pedophilia is limited but growing. It begins with a small study in the 1980s showing familiality of paraphilic behavior, including pedophilic behavior (Gaffney, Lurie & Berlin, 1984). Alanko, Salo, Mokros, and Santtila (2013) conducted the first study that I am aware of regarding the heritability of sexual interests, fantasies, and behavior involving children under the age of 16, using a twin design. This is not ideal because it would include not only persons with pedophilic interests but also persons with hebephilic and perhaps ephebophilic interests; very few respondents admitted to sexual interest or fantasy to children age 12 or younger. Nonetheless, the incidence of sexual interest in children under age 16 was 3%, and the concordance was higher for monozygotic than dizygotic twins. Heritability was estimated at 15%.

Långström, Babchishin, Fazel, Lichtenstein, and Frisell (2015) analyzed Swedish registry data, focusing on 21,566 men who had been convicted of a sexual offense between 1973 and 2009. Fathers (odds ratio [ OR ] = 3.7) and brothers (5.1) were much more likely to also have convictions for sexual offenses than paternal ( OR = 2.1) or maternal (1.7) half-brothers. Statistical modeling suggested that genetic factors explained 40% of the likelihood of sexually offending, compared with 58% for nonshared environmental and 2% for shared environmental factors. The evidence for genetic effects was stronger for sexual offenses involving children than for offenses involving adults (46% vs. 19%).

It would be surprising if pedophilia had no heritability, given evidence of moderate heritability for many other aspects of sexuality, including sexual orientation for gender (Bailey & Pillard, 1995), age at first intercourse (Dunne et al., 1997), interest in casual sex (Bailey, Kirk, Zhu, Dunne, & Martin, 2000), and excessive or public masturbation by children (Långström, Grann, & Lichtenstein, 2002). Similarly, it would be surprising to find no heritability for sexual offending against children, given robust evidence for moderate heritability of criminal and violent behavior (e.g., Frisell, Pawitan, Långström, & Lichtenstein, 2012; Walters, 1992). Heritability estimates might reflect variation in the traits or predispositions underlying pedophilia, such as the male-typical preference for youthfulness (see Quinsey & Lalumière, 1995; Quinsey, 2003).

Our understanding of pedophilia can be informed by advances in other areas, and indeed our understanding of other chronophilias could be advanced by using what has been learned about pedophilia to generate hypotheses. Growing evidence indicates nonexclusivity in age preferences, for example, individuals who are sexually interested in both prepubescent and pubescent children, or in prepubescent children and adults (Stephens, Seto, Goodwill, & Cantor, 2017a). This also has implications for the understanding of pedophilia and hebephilia in particular, because the overlap between these two forms very likely indicates common causes.

For example, future research may find that the structural and functional differences identified in this chapter for pedophilia may also be found in samples of persons with mesophilia or gerontophilia, suggesting differences are related to chronophilias other than teleiophilia more generally, rather than being specific to pedophilia. On the other hand, with finer resolution, researchers may find that some areas implicated in facial recognition are more activated when seeing young versus old faces, giving credence to the idea that activations reflect and direct interest in particular age groups. As another example, cross-sectional and longitudinal research may show that childhood sexual abuse history is specific to pedophilia or hebephilia, rather than other chronophilias, suggesting different psychosexual developmental trajectories are involved.

Research on other paraphilias may also be of value because of paraphilic comorbidity. Pedophilic individuals are more likely to engage in other paraphilic behavior than men randomly selected from the general population; for example, some pedophilic individuals have also engaged in exhibitionistic (12%–13%) or voyeuristic (11%–36%) behavior (Abel, Becker, Cunningham-Rathner, Mittelman, & Rouleau, 1988; Bradford, Boulet, & Pawlak, 1992; Chivers, Dawson, Curry, Bradford, & Seto, 2015; Freund, Seto, & Kuban, 1997). A troubling group are pedophilic men who are also biastophilic or sexually sadistic, because they would presumably be the most likely to use force or physically injure children (Chaplin, Rice, & Harris, 1995).

Blanchard et al.’s (2000) canalization hypothesis about pedophilia suggests neurodevelopmental perturbations disrupt normative sexual development, leading to the onset of one or more paraphilias related to the specific timing, location, and nature of these neurodevelopmental perturbations. Thus, men with paraphilias other than pedophilia might differ from nonparaphilic men in slightly different ways than pedophilic men differ from nonpedophilic men, but with overlap. Paraphilic comorbidity suggests that factors that increase the likelihood of one paraphilia increases the relative risk of others. The assumption is that multiple, pervasive, or intense perturbations can result in the development of multiple paraphilias. The fact that certain paraphilias tend to co-occur more often suggests an underlying structure to variations in sexual interests (e.g., courtship disorders of voyeurism, exhibitionism, and frotteurism; Freund & Seto, 1998; Freund et al., 1997).

It is not necessarily that pedophilic individuals are different in kind rather than in degree. A few studies have tackled this question. Mackaronis, Strassberg, and Marcus (2011) did not find a taxon, which would indicate pedophilia is a difference in kind, but their study was limited by focusing on three self-report scales from the Multiphasic Sex Inventory, only one of which was more specific to pedophilia (child molestation scale vs. sexual obsession and cognitive distortions/immaturity). Also, given taxometric analyses are power hungry, they had a relatively small sample of 371 sex offenders against children.

Schmidt, Mokros, and Banse (2013) also had a relatively small sample (for taxometric analysis purposes) of 304 men that was more heterogeneous than Mackaronis et al. (2011) because it included sex offenders against adults, non–sex offenders, and nonoffenders; 183 men had been convicted of contact offenses against children ( n = 155) or child pornography offenses ( n = 28). Schmidt et al. found evidence of a pedophilia taxon, comprising 27% of offenders with crimes involving children (45 contact and 4 child pornography offenders). As expected, members of this pedophilia taxon scored higher on measures of sexual interest in children, including the SSPI (only scorable for those with contact sexual offenses), viewing time, implicit association test, and self-report. Not quite consistent with previous research in that a higher proportion of the contact offenders (about half with boy victims) were assigned to the pedophilia taxon than the subgroup of child pornography offenders, even though past work suggests child pornography offenders are more likely to have pedophilia (Blanchard et al., 2007; Seto, Cantor, & Blanchard, 2006).

King (2010) did not conduct a taxometric study of pedophilia per se. Instead, he applied taxometric analysis to data from a large sample of 900 adult sex offenders considered for civil commitment. Of these 900 offenders, 366 had exclusively offended against victims age 16 or older; 353 had exclusively offended against victims under the age of 16; and the rest had both child and adult victims. Of those who had offended against victims under the age of 16, the majority (266) were deemed to be high in fixation using the Massachusetts Treatment Center typology for offenders against children, and thus were the most likely to be pedophilic. King identified a neurodevelopmental disorder taxon identified by low IQ, cognitive impairments (e.g., attention problems, learning disorders and symptoms of thought disturbance). This taxon overlapped with the high fixation group of offenders against children, but it could not be construed as a pedophilia taxon because only half (48%) of the probable 157 taxon members were high fixation offenders and these 76 overlapping offenders represented only 29% of the high fixation group. To illustrate the strength of the association, high fixation offenders against children were 2.8 times more likely to be in the taxon than their counterparts. The association was stronger for social competence than for high fixation among offenders against children, with those who were low in social competence being 4.3 times as likely to have taxon membership, suggesting the taxon may have more to do with a neurodevelopmental and social incompetence link than with pedophilia per se.

Gender and age interests interact in pedophilia. When assessed phallometrically, pedophilic men show less relative differentiation in their sexual arousal to boys versus girls than teleiophilic men do in their sexual arousal to men versus women (Freund & Kuban, 1993a; Freund, Watson, Dickey, & Rienzo, 1991). This probably reflects the fact that boys and girls are more similar in appearance than men and women, in terms of their body size and shape, and the absence of secondary sexual characteristics. However, it may also reflect a shift in the relative influence of gender and age cues, where gender cues are much more important for teleiophilic men. Among teleiophilic and exclusively gynephilic men, the greatest sexual response is to adult women, as expected, and then to adolescent girls, pubescent girls, and prepubescent girls, in that order (Blanchard et al., 2012). Sexual response to any female age/maturity category is usually higher than for any male category (Seto & Lalumière, 2001). In contrast, a pedophilic and gynephilic man may respond most to prepubescent girls, and then pubescent girls and prepubescent or pubescent boys.

Pedophilic men are more likely to be androphilic than teleiophilic men. Blanchard et al. (2000) found that 25% of the sex offenders with child victims preferred boys over girls, compared with general population estimates that suggest from 2% to 6% of men preferring men over women (Chandra, Mosher, & Copen, 2011; Laumann, Gagnon, Michael, & Michaels, 1994). In other words, same-sex attraction is approximately 5 to 10 times as likely among pedophilic than teleiophilic men. 4 This can also be explained by Blanchard et al.’s (2000) canalization hypothesis, whereby men who experience a perturbation in their age interests (teleiophilia to pedophilia) are also more likely to experience a shift in their gender interests (gynephilia to androphilia).

Blanchard et al.’s (2000) findings and canalization hypothesis fits well with Quinsey and Lalumière’s (1995) speculation that male sexual preferences are organized in a modular fashion: Some men show a shift in a hypothetical module for gender preferences (gay men), whereas others show a shift in a hypothetical module for age preferences (chronophilias other than teleiophilia). Men can also vary on other dimensions, including variations in self–other, living–nonliving, human–nonhuman, and dominance–submission, such that each person could be described in terms of how they place on a multidimensional sexual orientation space (see Seto, 2017b).

Etiological theories of pedophilia also need to be able to explain the large gender difference in the prevalence of pedophilia and hebephilia: Men are much more likely than women to seek child pornography or to engage in sexual offenses against prepubescent or pubescent children (Seto, 2013). Men are also much more likely than women to exhibit other kinds of paraphilias, except for masochism (Chivers et al., 2015).

The gender difference in pedophilia and sexual offending involving children is consistent with the large gender difference in the likelihood of engaging in crime and other antisocial behavior. But unlike the adaptive explanations proffered for males’ greater involvement in crime and other risk taking, it is highly unlikely that pedophilia has ever been adaptive for the individual with the condition, given the expected impacts of sexual interest in children on successful reproduction. Instead, the greater prevalence of paraphilias among men may reflect a generally greater susceptibility of men to developing neurodevelopmental conditions of many different kinds. Men are more likely than women to have conditions such as mental retardation, autism, and disorders, such that Gualtieri and Hicks (1985) described these conditions as selective male afflictions . Their hypothesis was that male-typical development is less canalized than female-typical development, because the fetal default is female in the absence of the organizing effects of testosterone. Lower canalization is then expressed in greater male variance across a wide range of traits, including extreme highs and lows. Thus, etiological theories of pedophilia and other paraphilias might gain a great deal from connecting consiliently to the larger literature on the etiology of male-biased conditions.

As this chapter shows, there are many major gaps in our understanding of pedophilia and hebephilia. By necessity, this chapter on etiology of pedophilia is more speculative than the previous chapter on the origins of sexual offending involving children. A major puzzle is how to explain pedophilia from a Darwinian perspective, because persons with pedophilia have fewer sexual contacts with sexually mature partners and, by definition, they are interested in nonfertile children. How could a condition that appears to be maladaptive be maintained in the general population? Even a small fitness disadvantage should cause a trait to disappear, without a counteracting effect that can maintain pedophilia at a low frequency in the population.

Despite the many unanswered questions about the etiology of pedophilia, progress has been made. It is particularly gratifying that some of the hypotheses discussed in the first edition have been empirically tested, such as the recent studies of minor physical anomalies and other indicators of prenatal causes. For the other hypotheses, there are some good thesis and project ideas here, reader! For example, the nature of the association between childhood sexual abuse and sexual offending against children or pedophilia still needs to be better understood. Cross-sectional studies, not all of which rely on self-report, have found childhood sexual abuse specifically predicts the onset or persistence of sexual offending, but longitudinal studies have not (Hanson & Morton-Bourgon, 2004, 2005; Widom & Massey, 2015). It is possible that childhood sexual abuse has an indirect effect through perturbations of psychosexual development that are not readily detected by following abused and nonabused children over time and looking at criminal records. Several studies suggest childhood sexual abuse is associated with an earlier onset of masturbation, pornography use, fantasies, and activity, which in turn may increase the risk of sexual offending through a sexual preoccupation path or simply greater opportunity (Das & Otis, 2016). Consistent with this idea, Kingston, Graham, and Knight (2017) found that adverse childhood experiences were linked to hypersexuality in identified male sex offenders, 60% of whom had offended against children. Longitudinal studies involving repeat interviews and self-report measures, along with collateral observations, are expensive and difficult but they would be invaluable. On another front, the understanding of the functional and structural networks underlying pedophilia is starting to cohere. However, more studies are needed with larger samples, unbiased analyses, and preferably both nonsexually offending and nonoffending controls (Cantor et al., 2015; Poeppl et al., 2015).

Theoretical explanations for pedophilia are not mutually exclusive. Different causal pathways may lead to pedophilia (equifinality) creating multiple forms of pedophilia rather than a single phenotype. This may explain some of the apparent heterogeneity in findings, including group differences, predictive associations, and estimates of heritability. A good etiological theory will need to incorporate this complexity. Even if all pedophilia reflected neurodevelopmental perturbations—which is unlikely to be the case, as not all pedophilic offenders who have been scanned or tested show brain differences or score low in IQ and other cognitive measures—those perturbations occur in different ways. An analogy can be drawn to other mental disorders, such as depression or schizophrenia, for which researchers increasingly recognize that different causal pathways lead to these conditions, and assessment and intervention strategies are more effective when they are fitted to the specific phenotype.

Many of the hypotheses discussed in this chapter are quite speculative, but they demonstrate how a Darwinian perspective can help produce novel and testable ideas. Pedophilia, and other chronophilias involving persons who are not sexually mature, are a major Darwinian puzzle. Another major puzzle is the understanding of incest, that is, sexual offenses involving close genetic relatives. In the next chapter , I focus specifically on sexual offenses against close, genetically related children, especially one’s own daughter. I discuss ultimate explanations for incest, based on inclusive fitness and other Darwinian considerations, with the hope that this leads to a more rigorous understanding of proximate explanations for incest that might include spousal relationship conflict, family dysfunction, atypical sexual interests, and antisociality.

2 I was incredibly fortunate to work during a golden age of sexology research at CAMH involving the sexual behavior clinic set up by Kurt Freund, a pioneer in phallometric research on pedophilia, and later involving Howard Barbaree, Ray Blanchard, James Cantor, Michael Kuban, Martin Lalumière, Ron Langevin, and Robin Wilson. Past trainees who have gone on to become successful researchers include Tony Bogaert, Meredith Chivers, Amy Lykins, and Skye Stephens.

3 This analysis replicated previous findings showing that criminal status is associated with significantly lower scores on intelligence, but sex offenders show an even bigger effect. Other criminology work has shown this not simply the result of a detection bias, where less intelligent offenders are more likely to be caught (Lynam, Moffitt, & Stouthamer-Loeber, 1993; Moffitt & Silva, 1988). Instead, intelligence can be seen as a stand-in for relevant psychological traits, such as planning; problem solving; and capacity to gain goals through prosocial means, such as education and work.