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European Journal of Criminology

DOI: 10.1177/1477370806059082 2006; 3; 85 European Journal of Criminology

Mons Bendixen, Inger M. Endresen and Dan Olweus Self-Reported Antisocial Behaviour in Early Adolescence

Joining and Leaving Gangs: Selection and Facilitation Effects on

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Joining and Leaving GangsSelection and Facilitation Effects on Self-Reported

Antisocial Behaviour in Early Adolescence

Mons BendixenNorwegian University of Science and Technology, Norway

Inger M. EndresenUniversity of Bergen, Norway

Dan OlweusUniversity of Bergen, Norway

A B S T R A C T

Gang membership is repeatedly reported to be one of the strongest predictorsof antisocial behaviour. However, whether this association primarily reflects aselection effect or whether it primarily is related to a facilitation of antisocialbehaviour within the gang has scarcely been an object of empirical study. Thispaper examines how antisocial behaviour and gang membership are associatedamong adolescents across time, using longitudinal data from a representativesample of Norwegian adolescents (N = 1203). Initial cross-group comparisonsrevealed that gang members were markedly more involved in general antisocialbehaviour than non-gang members not only during periods of active gangmembership but also during other periods, thereby supporting the theory thatthere is a selection effect. This effect was smaller for violence than for otherforms of antisocial behaviour. Results from longitudinal analyses that comparedbehavioural changes among gang members and non-gang members duringperiods when the gang members joined and left a gang demonstrated thatactive gang affiliation strongly facilitated general antisocial behaviour as well asviolent behaviour. Taken together, the results give strong support to the theorythat both selection and facilitation processes contribute to the associationbetween gang membership and antisocial involvement.

K E Y W O R D S

Gang Membership / Antisocial Behaviour / Violence / Selection / Facilitation.

Volume 3 (1): 85–114: 1477-3708DOI: 10.1177/1477370806059082

Copyright © 2006 European Society ofCriminology and SAGE Publications

London, Thousand Oaks CA, and New Delhiwww.sagepublications.com



Introduction

The association between an individual’s involvement in antisocial behav-iour and gang membership is one of the strongest and most consistent inthe criminological literature (Elliott et al. 1985; Elliott and Menard 1996;Thornberry et al. 1994). Regardless of methodology and design, empiricalstudies repeatedly have shown that adolescents who are members of a gangare markedly more involved in antisocial behaviour than their non-memberpeers (for an overview, see Spergel 1990). The membership effect has beendemonstrated across a great variety of behaviours such as theft, burglary,vandalism, truancy, drug sales and drug use, and is especially strong formore serious and violent offences (Thornberry et al. 1993).

Although the association between gang membership and antisocialbehaviour appears indisputable, criminologists seem to disagree about thetemporal sequence of the two factors, and whether the factors are causallylinked or not. According to Thornberry and associates (1993), the mechan-isms underlying this relationship are poorly understood owing to the lackof longitudinal data.

The general shortcoming of cross-sectional designs in disentanglingtemporal events makes these designs insufficient for drawing any conclu-sions regarding the nature of the link between antisocial behaviour andgang membership (Thornberry et al. 1993; Henry et al. 1994; Tonry et al.1991: 27–9). To understand better how gang membership influences in-dividuals’ antisocial behaviour across time, members and non-gang mem-bers must be followed long enough to observe their behaviour before,during and after periods of active gang membership.

Thornberry and colleagues (1993) have outlined three models as abasis for exploring the temporal sequence and underlying processes for thestrong gang–delinquency association. The first model focuses on the forma-tion of the gang and the selective affiliation processes that take place priorto gang formation. In this model, it is assumed that gangs recruit memberswho already are delinquent, or at least have a high propensity for delin-quency, before joining the gang (the selection model). The second modelemphasizes the facilitation or social learning processes that take placewithin the gang and among gang members. In this model, gang member-ship is considered to be a major cause of the increased delinquency amonggang members (the social facilitation model). The third model is based ona combination of the first two, and the underlying assumption is that socialfacilitation and selection processes may work together in forming thestrong association between gang membership and antisocial behaviour.Thornberry et al. use the term enhancement model for this combinedmodel. A short presentation of the three models, their theoretical basis and

86 European Journal of Criminology 3(1)



their implications for antisocial behaviour before, during and after activegang involvement follows.

Explanatory models

In the first model, it is assumed that peer selection is the main processaccounting for the strong relationship between delinquent behaviour andgang membership. The selection model contends that gangs primarilyattract adolescents already involved in antisocial and deviant behaviourand that virtually no new behaviour is generated at the individual level asan effect of joining a gang. Rather, the increased levels of antisocial anddeviant behaviour associated with gangs are truly an effect of antisocialelements ‘flocking together’. Several studies have found that adolescentstend to select friends with similar backgrounds, attitudes and personalitytraits as themselves (see review by Rowe et al. 1994). For example, Kandel(1978) found in her study of friendship pairs that the vast majority offriendship similarity in minor delinquency was the result of selection andthe average influence effect was small. In their General Theory of Crime,Gottfredson and Hirschi claim that ‘adventuresome and reckless childrenwho have difficulty making and keeping friends tend to end up in thecompany of one another, creating groups made up of individuals who tendto lack self-control’ (1990: 158). In short, they consider lack of self-controlto be the primary determinant of crime and analogous acts through itsinteraction with crime opportunity. Gang members are assumed to perceivereduced risks of sanctions by diffusing and confusing the responsibility fortheir acts; gangs or groups ‘act as a mask and a shield, as a coverfor activities that would not otherwise be performed’ (Gottfredson andHirschi 1990: 209). Within this framework, the gang does not so muchinstigate the production of antisocial behaviour as reduce the probability ofgetting caught. However, even if gang membership may be perceived as anopportunity factor (Huang et al. 2001), opportunity is not considered tohave an independent effect on antisocial behaviour beyond its interactionwith self-control according to Gottfredson and Hirschi’s theory. The pre-dictions from the selection model are that gang membership followsantisocial/delinquent behaviour, and joining or leaving a gang is notlikely to produce any major changes in antisocial behaviour at theindividual level.

A largely different explanation for the strong gang–delinquencyassociation is provided by the social facilitation model. This model, whichemphasizes the socialization processes within the gang, does not considergang members to be particularly different from non-members prior to or

Bendixen, Endresen and Olweus Joining and leaving gangs 87



after their periods of active membership. The group norms and varioussocial processes activated by the gang are thought to facilitate involvementin delinquency and violence, and gang membership is viewed to be a majorcause of deviant behaviour. Changes in antisocial/delinquent involvementare assumed to follow changes in gang membership status.

This model is compatible with socialization theories, such as differ-ential association theory or social learning theories (Sutherland and Cressey1978; Akers 1997). The typical temporal sequence proposed by Akers isthat associations with delinquent peers will precede delinquency: ‘thesequence of events, in which deviant associations precede the onset ofdelinquent behavior, will occur more frequently than the sequence of eventsin which the onset of delinquency precedes the beginning of deviantassociations’ (1997: 69). The groups with which one is in differentialassociation are essential in this theory, since they are assumed to providethe major social contexts in which all the mechanisms of social learningoperate. According to the facilitation model, an increase in antisocial/delinquent behaviour after joining a gang is expected and a decrease afterleaving the gang, since the learned behaviour will no longer receive enoughsocial support and reinforcement to be sustained.

The enhancement model, proposed by Thornberry et al. (1993), is amixed model based on the assumption that both selection and socialfacilitation processes contribute to the association between gang member-ship and delinquent behaviour. In this model, gangs are assumed to recruittheir members from adolescents who are already delinquent. Further, sincegangs provide an atmosphere that encourages delinquency and sometimesmakes it easier, delinquent behaviour will be facilitated.

Several authors have integrated aspects from control theory andsocial learning theory into combined explanatory models (for an overview,see Akers 1997; Thornberry and Krohn 1997). Thornberry (1987; Thorn-berry and Krohn 2001) has proposed an interactional theory of delin-quency, which is considered to be a theoretical elaboration rather than atheoretical integration of prior theories. This perspective holds that bothprocesses (deviant behaviour leading to deviant peer associations anddeviant peers contributing to increased deviance) operate to producedeviant behaviour over the life course (Thornberry and Krohn 1997). Inthis theory, the fundamental cause of delinquency is assumed to beweakened social constraints (Thornberry 1987). However, what is requiredif the freedom resulting from weakened bonds is to be channelled intoserious and prolonged delinquency is an interactive setting in whichdelinquency is learned, performed and reinforced (Thornberry 1987: 865).According to the enhancement model proposed by Thornberry et al. (1993,2003), one would expect higher rates of delinquency among gang members




than among non-gang members before joining a gang owing to socialselection and a significant increase after joining a gang owing to thefacilitation effect.

In the present study, the proposed mixed enhancement model will beexamined along with the facilitation model and the selection model. Weconsider the models outlined by Thornberry et al. (1993) to be a usefulbasis for an exploration of the contribution of selection and facilitationprocesses to the association between gang membership and antisocialbehaviour or delinquency, and our design is clearly influenced by theirstudy. Before turning to the description of the present study, we will discussthe available longitudinal research that has focused on these questions.

Prior research

Prior published studies on how the level of involvement in antisocialbehaviour is associated with joining and leaving antisocial gangs are scarce.Longitudinal studies examining this issue have been reported by Esbensenand Huizinga (1993), using data from the Denver Youth Study, by Thorn-berry et al. (1993, 2003), using data from the Rochester Youth Develop-ment Study, and by Lacourse et al. (2003), who used data from theMontreal Longitudinal Experimental Study. Recently, Gordon and col-leagues (2004) reported on results from the Pittsburgh Youth Study. Inaddition, results from an unpublished study by Hill et al. (1996) using datafrom the Seattle Social Development Project have been briefly summarizedby Thornberry (1998).

Esbensen and Huizinga (1993) concluded from their study of a ‘high-risk’ neighbourhood sample of principally African-American and Hispanicmales and females that gang members were, compared with non-gangmembers, more involved in ‘street offences’ (theft, violence, selling drugs,etc.) and ‘serious offences’ (theft, violence, vandalism, fraud, etc.) prior toand after periods of active gang membership. To a lesser extent, this wasalso true for the category of ‘illicit drug use’. During the year of activemembership, however, Esbensen and Huizinga reported that the gangmembers’ involvement was substantially higher than non-members’ in-volvement irrespective of the offending category. In general, their analysessupported a mixed model, even if the social facilitation effect was strongerthan the effect of social selection.

Thornberry et al.’s (1993) study involved a sample of boys fromRochester, New York. Separate analyses were performed on various groupsof transient and stable gang members over a period of three years. Thedependent variables were ‘person offences’ (violence), ‘property offences’




(including acts of vandalism, theft, joy-riding and fraud), ‘drug sales’, ‘druguse’ and a ‘general delinquency’ index covering the items from the firstthree categories. Regarding the transient gang members, who stayed in thegang for no more than one year, they concluded that their data were mostconsistent with the social facilitation model. A notable exception was thecategory ‘property offences’, which turned out to be relatively insensitive tochanges in gang membership status. Transient gang members were notsignificantly more involved than non-members in any of the categoriesanalysed in periods before and after active gang membership. This was alsotrue of stable gang members (who were active gang members for at leasttwo consecutive years), with the notable exception of the ‘general delin-quency’ index, for which the analyses demonstrated selection as well asfacilitation effects. Thornberry and associates maintained that the ‘strong-est support for the facilitation model is found in the analysis of the type ofbehavior most often associated with gangs – crimes against the person’(1993: 80).

Recently, Thornberry and colleagues published additional analyses ofthe Rochester study including data from the fourth year (Thornberry et al.2003). By applying more advanced multivariate models that also controlledfor unmeasured characteristics of the individual, they were able to separatethe effects of selection from those of facilitation. Similar to their earlierresults, these new analyses showed that selection effects were generallysmall or modest across the various domains of antisocial behaviour,and facilitation effects were strong and consistent in these more recentanalyses too.

Lacourse et al.’s (2003) study of violent behaviour among a sample ofwhite, French-speaking adolescents of low socioeconomic status largelysupported Thornberry et al.’s (1993) findings. The results from the Mon-treal study showed that transitions into delinquent groups significantlyincreased involvement in violent offending whereas transitions out ofdelinquent groups were associated with decreased levels of violent offend-ing. Slightly elevated levels of violence were also present before joiningdelinquent groups, suggesting some selection effect. However, this effectwas evident only among students with a history of childhood delinquentbehaviour.

Thornberry’s (1998) summary of the unpublished results from theSeattle sample suggests that the mean levels of violence were found to beespecially elevated during the year of active gang membership and sub-stantially reduced after active membership. Although the level of violencewas somewhat higher before joining a gang, Thornberry (1998) concludedthat the results were most consistent with the social facilitation model. The




selection effect was less consistent and less powerful than the demonstratedfacilitation effect.

Similarly to Thornberry et al.’s more recent results, Gordon andcolleagues’ (2004) also found evidence for selection effects across differentdelinquency outcomes in their study of a representative sample of boys inpublic schools in Pittsburgh. By using advanced multiple regression modelsthey were able to adjust for unmeasured pre-existing individual differencesas well as controlling for age, seasonality and calendar time trends. Still, theauthors report that the most consistent finding was that the boys reportedmore drug sales, drug use, violent and property delinquency in periodswhen they were active members compared with periods before and afteractive gang involvement.

Although the most consistent findings regarding the gang–delinquency relationship have pointed to the strong socialization effectsthat take place within gangs, these recent studies indicate that selectionprocesses are also at work. This is further underlined in a number oflongitudinal studies that have uncovered risk factors for later gang mem-bership through the use of different analytic methods. For example,bivariate analyses have shown that violence and externalizing problems(Hill et al. 1999) and conduct disorders and self-reported delinquency(Lahey et al. 1999) were among the strongest predictors for later becominga gang member. In addition, Thornberry and colleagues (2003) found thatviolent delinquency predicted gang membership for males when the effectsof other predictors across various domains were controlled for.

In sum, the Denver, Rochester, Montreal, Seattle and Pittsburghstudies clearly support a facilitative effect of gang membership across avariety of antisocial behaviours. Violent behaviour seems to be particularlystrongly related to gang membership in demonstrating increased levels ofoffending mainly in periods of active membership. Still, the Denver YouthStudy taken together with the more recent findings from the Rochester andPittsburgh studies and the studies on risk factors for gang entry indicatesthat some selection effects are present.

Drawing strongly on the previous studies, this paper investigates howgang membership is associated with antisocial involvement across time in arepresentative sample of Norwegian, predominantly white, adolescents.More specifically, we want to examine the magnitude of the selection andfacilitation effects for general antisocial behaviour and interpersonal vio-lence. Questions raised are:

1. Do gangs primarily attract adolescents already involved in antisocial behaviour, ordo gangs primarily facilitate antisocial behaviour?

2. Does the magnitude of these two effects differ between general antisocial behav-iour and violence, as indicated in prior studies?




Since no results have yet been published from European studies on thelongitudinal association between involvement in antisocial behaviour andgang membership, this study helps to show whether the conclusions drawnfrom North American studies can be more widely generalized.

Methods

The present study is part of a large-scale, longitudinal research programmeon ‘The school as a context for social development’ under the direction ofDan Olweus. The main focus of the project was on bullying in school and,particularly, on the effects of a school-based intervention programme inreducing such problems (see, e.g., Olweus 1991, 1993a, 1993b, 1994,2005). The data used in the present study were collected in May/June 1983,here designated Time 1, in May/June 1984 (Time 2) and in May/June 1985(Time 3). It should be noted that the Olweus Bullying Prevention Pro-gramme was implemented in the period between Time 1 and Time 2. It hasbeen documented that the programme had positive effects on the level ofbullying as well as on substance use and antisocial behaviour in general(e.g. Olweus 1991, 1994).

Sample

Data were collected from four relatively large cohorts of students from thecity of Bergen in Norway. Bergen, with slightly more than 200,000inhabitants, is the second-largest city in Norway. The subjects participatingin the project were in grades 5–8 (according to the current grade designa-tion system) at Time 1. However, only students in grades 7 and 8 wereasked questions about membership of antisocial gangs.

Subjects in classes at the same grade, who were therefore of approxi-mately the same age, were regarded as belonging to a cohort (Olweus andAlsaker 1991). The classes to be included in each cohort were selected atrandom from all those at the relevant grade in Bergen. Hence, each cohortis broadly representative of students in the relevant grade in schools inBergen; also, students in Bergen are to a large extent representative of thosethroughout towns in Norway. Close comparisons between the cohorts arepossible, because each is representative of students in the relevant grade,and the methods of selection used for students in each grade werethe same.

A total of 56 classes (28 at each grade level) drawn from 28elementary schools (grade 7) and 14 secondary/junior high schools (grade8) participated. The modal age for students in grades 7 and 8 at the firstmeasurement occasion (Time 1) was 13 and 14, respectively. The total




number of students who answered the questionnaire on antisocial behav-iour at Time 1 in these cohorts was 1292 (586 girls and 706 boys). Thisrepresents 93.8 percent of the total eligible sample of 1377 students. AtTime 2, 79.8 percent of these students were still in the project, and 75.2percent of the Time 1 students participated at Time 3. The number ofstudents with valid longitudinal data at at least two of the three time pointswas 1203.

Previous analyses have shown that students who were particularlystrongly involved in antisocial behaviour dropped out of the study indisproportionate numbers at Time 2 or Time 3 (Bendixen and Olweus1999). This selective attrition may have reduced the initial selection effectfor joining gangs because some of the most extreme subjects were notavailable for analysis.

Procedure

The subjects answered the questions about antisocial behaviour (as well asother relevant questions) in their regular classrooms. Two research assis-tants administered the questionnaires with the teacher absent. Each meas-urement occasion lasted for two or three school periods of 45 minutes each.The students were encouraged to give sincere answers to the questions, andthey were told that their responses would be confidential (confidentialitywas achieved by means of a code system). Detailed instructions about howto respond were written on the front page. The research assistants read thisaloud in the class and an example was given. The assistants were availablefor help during the whole session.

Measurements

Two dependent variables were used in the present study: general antisocialbehaviour (Total scale of antisocial behaviour, 17 items) and violentbehaviour (Violence scale, 5 items on violence and causing trouble in publicnot covered by the total scale). The wording of the items covered bythe scales is shown in the appendix. The scores on the total scale and theviolence scale were based on item responses reflecting participation or non-participation in the depicted antisocial act in the specified period – ‘thisspring term’ (approximately five months). The response alternative ‘at notime this spring’ was coded as ‘0’, whereas having committed the behaviourin question one or more times during the spring was coded as ‘1’. Thescores on the items were added to form a composite score reflecting thevariety of antisocial acts. A subject’s variety score, which is a sum score,indicates the range or number of different offence types or antisocial acts of




a certain category in the specified period admitted to by the subject . As anindicator of the internal consistency of the scales, Cronbach’s alpha for thetotal antisocial behaviour scale (boys and girls in the two cohorts pooled)was .78 (Time 1), .81 (Time 2) and .76 (Time 3). The corresponding valuesfor the violence scale were .61 (Time 1), .77 (Time 2) and .65 (Time 3). Theraw stability coefficients (Pearson’s r) between Time 1 and Time 2 (one-yearinterval) were .58 and .35 for the total scale and the violence scale,respectively. Between Time 1 and Time 3, the stability coefficients were .45(total scale) and .30 (violence scale). More details about the development ofthe scales and their psychometric properties, reliability and constructvalidity are given in Bendixen and Olweus (1999).

The main independent variable in this study was gang membership.Although there is some controversy regarding the definition and identifica-tion of a gang (see Spergel 1990; Klein 1995; and Curry and Decker 1998for reviews), the identification of a gang member is a rather straightforwardprocess. According to Curry and Decker, ‘the most powerful measure ofgang membership is self-nomination’ (1998: 6). Support for this assertion isfound in a large number of studies using diverse methodologies such as self-reports, interviews and police records. On each of the three measurementoccasions, cohort members were asked three questions: ‘Have you (duringthe past five months): (1) Been a member of a group or gang that hasvandalized property (destroyed things like benches, seats in a movie or abus, telephone booths, etc.)? (2) Been a member of a group or gang that hasbullied or pestered other people? (3) Been a member of a group or gangthat has drunk alcohol and then been noisy and rowdy?’ The surveyquestions differed somewhat from those posed by Thornberry et al. (1993)and Esbensen and Huizinga (1993). Thornberry and associates asked therespondents only whether they belonged to a street gang, without seekingany further information on the gang’s illegal orientation or activity, colours,signs, organization or turf. Esbensen and Huizinga, on the other hand,asked follow-up questions in order to discriminate members of criminalgangs from respondents who were part of informal youth groups. Althoughthe questions asked in this study differed somewhat from those used byEsbensen and Huizinga, the content of the questions was basically similar;both sets of questions clearly emphasized the antisocial or criminal dimen-sion of gang activity.

On each of the three measurement occasions, between 9 percent and11 percent of the students responded ‘yes’ to at least one of the three gangquestions. The majority of the students were involved in ‘drinking anddisorder’ gangs. Being a gang member in one domain (vandalism, bullying,or drinking and disorderly) was highly correlated with membership in




another domain (Pearson’s r for dichotomous items averaged .40), andCronbach’s alpha for the gang membership variable was above .60 on eachof the three measurement occasions. However, there was a notable changeof emphasis between the domains over the three measurement occasions.Among those who continued as gang members, an increasingly largerproportion got involved in the ‘drinking and disorder’ domain across timeat the expense of involvement in the ‘vandalism’ and the ‘bullying’ do-mains. Acknowledging both the relatively strong inter-correlations betweenthe three domains, and that the most common antisocial behaviour patternduring the adolescent years involves different types of behaviour (see, e.g.,Klein 1984), we decided to treat gang membership as a single conceptstraddling the three domains. If cohort members answered ‘yes’ to one ormore of the three gang questions on any measurement occasion, they wereconsidered gang members.

Table 1 shows a sample matrix describing the gang affiliation of thevarious groups organized according to the stability of their membership.The transient gang members said they were active on one of the threemeasurement occasions only, whereas the stable gang members said theywere active on two or three of the measurement occasions. Included in thematrix are students who completed the questionnaire on at least two ofthe three occasions (e.g. gang member at T1, absent at T2, not a gangmember at T3 was classified as transient member, Time 1 only). Because thefive-month reference period covers only approximately half of the totaltime-span of three years, we may have missed a few gang members whowere active only between the reference periods. However, we do not thinkthis problem is large. As described in Bendixen and Olweus (1999), themain advantage of using the five-month period (‘this spring term’) ratherthan the more conventional 12-month reference period was that it repre-sented a more natural memory unit to the students.

As we can see from Table 1, 249 of the students (almost 21 percentof the sample of 1203) said they were gang members on at least one out ofthree measurement occasions. Being a gang member was, however, a ratherunstable characteristic. Three out of four gang members (190 out of 249)were active members at only one point in time, and are defined here astransient members. Gang members (both transient and stable) accountedfor 24 percent of the male students and 17 percent of the female students;38 percent of gang members were females. Despite this substantial involve-ment of females (see also Bjerregaard and Smith 1993 and Esbensen andHuizinga 1993), the stable gang members were predominantly boys. Gangmembers of both sexes were predominantly students from the older of thetwo age cohorts (two out of three).




Analyses

In our early investigations we performed separate analyses on the differentsub-groups of gang members, producing a rather complicated picture of theeffects of gang membership on antisocial behaviour. Taking account of thiscomplexity, two types of analyses were performed: (1) cross-group analy-ses, contrasting involvement in antisocial behaviour and violence for non-gang members versus gang members in non-active periods; and (2)longitudinal analyses comparing (a) the same subjects in active versus non-active periods of gang membership, and (b) change across time in antisocialand violent behaviour among gang members versus non-gang members(group by time effects). Initially, boys and girls were analysed together, butsupplementary analyses were later performed on the male sub-sample.

Cross-group differences were analysed using independent samples t-tests for each of the three measurement occasions. When the assumptionabout equal variance in the groups compared was not met, the ‘unequalvariance’ procedure in SPSS with corrected degrees of freedom was used.Profile analyses (the GLM repeated measures procedure in the SPSSpackage) were applied for comparisons of the cross-time changes.

In addition to tests of significance, effect sizes (d) were computed forindependent and dependent samples using the formulas advocated byCortina and Nouri (2000).1 For the computations of effect sizes reflecting

1 In estimating the effect size for independent samples with unequal group sizes, we usedformula (1.5): d = t [(1/n1) + (1/n2)]

.5 in Cortina and Nouri (2000). Formula (1.5) was alsoused for estimating group differences for difference scores. In estimating the effect size fordependent (correlated) samples, formula (5.2): d = tr [2(1 – r)/n].5 in Cortina and Nouri(2000) was used.

Table 1 Sample matrix for describing antisocial gang affiliation at three times

Time 1 Time 2 Time 3 n

Non-gang members Non-active Non-active Non-active 954

Transient gang membersTime 1 only Active Non-active Non-active 77Time 2 only Non-active Active Non-active 50Time 3 only Non-active Non-active Active 63

Stable gang membersTimes 1 and 2 only Active Active Non-active 19Times 1 and 3 only Active Non-active Active 13Times 2 and 3 only Non-active Active Active 17Times 1, 2 and 3 Active Active Active 10




group differences over time, the mean differences in the scores between thetwo points of time were used in the formula. The main advantages of usingeffect sizes over tests of significance are that effect sizes permit more directcomparisons of results across studies, and that the magnitude of theselection and facilitation effects can be estimated. However, when the as-sumptions of homogeneity of variance and equal sample sizes are not met(as would be expected when comparing gang members with non-gangmembers), the calculated effect size estimates in these samples may besubstantially different from those in the population and must be interpretedcautiously (Cohen 1977). To meet the risk of overestimation, we usedseparate variance t-values in Cortina and Nouri’s formula (1.5).

Hypotheses

From the three explanatory models outlined in the introduction, severalhypotheses can be generated:

• The selection model will be supported if:

1. gang members are more involved in general antisocial behaviour andviolence than are non-gang members whether or not they are currentlyactive members (cross-group comparison), and

2. changes in gang members’ involvement in general antisocial behaviour andviolence are virtually unrelated to whether they are entering or leavinggangs (cross-time comparison).

• The social facilitation model will be supported if:

3. gang members are more involved in general antisocial behaviour andviolence than are non-gang members only in periods when they are activemembers; in non-active periods their behaviour will not differ greatly fromthat of the non-gang members (cross-group comparison), and

4. changes in gang members’ involvement in general antisocial behaviour andviolence are related to whether they are entering or leaving gangs (cross-time comparison).

• The enhancement model will be supported if hypotheses 1 and 4 are confirmed.

Results

General antisocial and violent behaviour: Descriptive analyses

Across the three time periods, approximately half of the sample of non-gang members had committed at least one of the antisocial acts covered bythe total scale of antisocial behaviour during the previous five months. Incomparison, 80 percent of the transient gang members and more than 90




percent of the stable gang members had committed such an act. The genderdifference in antisocial participation was negligible. Regarding violentbehaviour, less than 10 percent of non-gang boys committed an act ofviolence during the previous five months. For girls who were not gangmembers the participation rate was markedly lower at 3.5 percent. Bycomparison, in the case of transient gang members, 25 percent of boys and11 percent of girls participated in violence. Stable gang members demon-strated the highest rate of participation in violent behaviour: approximately50 percent of the boys and more than 30 percent of the girls had committedan act of violence during the previous five months. In sum, these resultssuggest that, although general antisocial and violent behaviour wasstrongly linked to gang membership, not every gang member was involvedin general antisocial behaviour and a fairly substantial proportion were notinvolved in violent behaviour.

The mean scores on the total scale of antisocial behaviour are shownin Table 2. The original variety scores, which reflect the number of acts(between 0 and 17) that an individual had committed, have been recali-brated so that the range is 0–100. The figures in Tables 2 and 3 were basedon the total number of students responding at the time period in question:numbers are smaller for analyses requiring data from more than one timeperiod for the same student. As can be seen from Table 2, gang memberswere markedly more likely to be involved in general antisocial behaviourthan were non-gang members, and this remained true in periods before andafter active gang membership, and particularly during periods of activegang membership.

Involvement in violent behaviour was lower than for general anti-social behaviour (see Table 3). However, the pattern of involvementobserved for general antisocial behaviour was largely replicated for violentbehaviour, suggesting that involvement in violent behaviour was particu-larly strong in periods of active gang membership.

Cross-group differences

Between-groups t-tests were performed in order to examine hypotheses 1and 3 regarding gang members’ antisocial involvement in periods when notactively involved in gangs. These analyses contrasted non-gang memberswith gang members in non-active periods on each of the three measurementoccasions. The results from the analyses are displayed in Table 4.

As can be seen from the upper panel of Table 4, non-active gangmembers scored significantly higher on the total scale of antisocial behav-iour than did non-gang members at all the three points of time. At T1,before joining the gang, non-active gang members (covering the ‘Time 2




only’, ‘Time 3 only’ and ‘Time 2 and 3 only’ groups) scored 0.65 standarddeviation units above non-gang members. Furthermore, the effect sizes (d)were moderate to large for non-active gang members at T2 (covering the‘Time 1 only’, ‘Time 3 only’ and ‘Time 1 and 3 only’ groups) and moderateat T3 after active membership (covering the ‘Time 1 only’, ‘Time 2 only’and ‘Time 1 and 2 only’ groups). Across the three time periods, the groupdifferences averaged 0.59 standard deviation units, and were even morepronounced when boys were analysed separately (d = 0.67). These resultsclearly support hypothesis 1 and the presence of a selection effect.

The results for the violence scale, displayed in the lower panel ofTable 4, showed that non-active gang members were significantly moreinvolved in violent behaviour than were non-gang members on all threemeasurement occasions. However, the group differences were less markedthan for general antisocial behaviour and averaged one fourth of a unit ofstandard deviation across the three time periods. For boys, the groupdifferences were equally small and non-significant at Time 1 and Time 3(before and after joining the gang). Although social selection seems to be a

Table 2 Mean scale scores on the total scale of antisocial behaviour: age 13 and age 14

cohorts

n Time 1 Time 2 Time 3

Non-gang members 954 7.7(8.8)

6.4(7.2)

6.2(6.0)

Transient gang membersTime 1 only 77 25.2

(29.4)13.3

(16.2) 10.3

(12.3)Time 2 only 50 17.2

(21.1)24.8

(32.2)13.7

(16.3)Time 3 only 63 17.2

(18.4) 16.7

(18.9)19.0

(19.6)

Stable gang membersTimes 1 and 2 only 19 36.2

(50.3)47.8

(58.2)17.3

(16.7) Times 1 and 3 only 13 37.4

(43.6)23.3

(27.8) 20.9

(24.6)Times 2 and 3 only 17 14.4

(15.6) 27.2

(26.3)25.3

(29.6)Times 1, 2, and 3 10 43.1

(47.2)44.5

(43.8)43.1

(45.1)

Note: Boys’ scores in parenthesis.




less crucial factor in explaining the association between gang membershipand violent behaviour among adolescents, the presence of a small selectioneffect suggests that hypothesis 1 cannot be rejected.

Analyses with repeated measures

Two sets of profile analyses were carried out for further examination of thefacilitative effect of active gang membership on antisocial and violentbehaviour. First, we made a rough comparison of gang members’ antisocialand violent behaviour in active versus non-active periods, using meanscores in active and passive periods for all gang members who were notactive throughout and across all measurement occasions, with the subjects’sex as a between-groups factor. Second, we compared the profiles of gangmembers in periods of joining and leaving with those of non-gang mem-bers. If the profiles of the two groups were significantly different, thiswould appear as a significant interaction (Time x Group) effect in theanalysis. In these analyses, subjects’ sex was included as a covariate.

The within-group analyses clearly showed that gang members’ in-

Table 3 Mean scale scores on the violence scale of antisocial behaviour: age 13 and age 14

cohorts

n Time 1 Time 2 Time 3

Non-gang members 954 2.6(4.2)

1.4(2.3)

1.1(1.6)

Transient gang membersTime 1 only 77 12.0

(16.3)5.5

(8.4)2.8

(3.9)Time 2 only 50 5.5

(9.2)14.3

(24.8)4.4

(6.3)Time 3 only 63 5.1

(5.9)3.3

(3.5)9.7

(13.1)Stable gang members

Times 1 and 2 only 19 23.2(38.0)

27.4(46.0)

6.2(6.7)

Times 1 and 3 only 13 15.3(20.0)

4.0(5.7)

18.5(24.4)

Times 2 and 3 only 17 5.0(6.0)

22.4(21.7)

13.8(20.0)

Times 1, 2 and 3 10 29.0(33.8)

28.9(25.7)

20.0(20.0)

Note: Boys’ scores in parenthesis.




volvement in general antisocial behaviour was markedly higher in periodsof active membership than in non-active periods for the same individuals(F(1,152) = 29.35, p < .001). The overall effect size of this within-groupdifference was moderate (d = 0.46). The difference between active andnon-active periods did not differ significantly for boys and girls (non-significant Time x Sex interaction).

As in the case of general antisocial behaviour, gang members weresignificantly more involved in violent behaviour in periods when theywere active members than in periods when they were non-active(F(1,152) = 15.88, p < .001). The overall effect size of this difference wasmoderate (d = 0.42). However, a significant Time x Sex interaction(F(1,152) = 10.97, p < .01) was evident for violent behaviour; thedifference between active and non-active periods was markedly larger forboys than for girls. In sum, these results show that active gang membershipis associated with high levels of general antisocial behaviour as well asviolent behaviour (supporting hypothesis 4). The following paragraphs

Table 4 Between-group differences in antisocial and violent behaviour for non-gang

members vs. gang members in periods of non-active membership: age 13 and age 14

cohorts

Mean score (s.d.)

Non-gang Gang(non-active) d.f. t d

Antisocial behaviourT1 7.7 (10.2)

8.8 (10.6)17.0 (14.8)18.9 (15.8)

129.386.3

6.56***5.43***

0.650.67

T2 6.4 (10.0)7.2 (11.3)

15.6 (14.9)18.6 (15.8)

127.083.3

6.47***5.89***

0.640.75

T3 6.2 (9.7)6.0 (9.8)

12.2 (12.7)13.9 (13.4)

132.665.8

4.85***4.29***

0.490.60

Violent behaviourT1 2.6 (8.9)

4.2 (11.2)5.2 (12.7)6.9 (13.8)

128.790.7

2.12**1.66 n.s.

0.210.21

T2 1.4 (6.9)2.3 (9.0)

4.4 (10.9)5.8 (12.8)

125.583.3

2.83**2.28*

0.280.29

T3 1.1 (6.4)1.6 (7.9)

3.7 (10.9)4.8 (13.1)

125.363.0

2.47*1.82 n.s.

0.250.26

Note: Boys’ figures in italic.t- and d-values are based on separate variance estimates.*p < .05, **p < .01, ***p < .001, n.s. non-significant




describe the results of more detailed analyses of behavioural changes ingang members compared with non-gang members during periods whengang members leave or join gangs.

For gang members, four events were identified and analysed. Gangmembers could either be leaving or joining a gang between Time 1 andTime 2, or be leaving or joining a gang between Time 2 and Time 3.Students who joined or left a gang at a particular time were groupedtogether regardless of whether they were transient or stable gang members.Non-gang members, who constitute the vast majority of the cases analysed,by definition experienced no joining or leaving events across the threemeasurement occasions. Any change in behaviour for these subjects mustbe attributable to factors other than leaving or joining gangs, and thesenon-gang members serve as ‘controls’ in the analyses.

The results of the analyses of the total scale of antisocial behaviourare displayed in the upper panel of Table 5. Only interaction effects arereported. Significant Time x Group interaction effects were demonstratedfor all events except for ‘Joining between T2 and T3’. For the significantresults, the effect sizes of the difference scores were generally large. Onaverage, leaving or joining a gang produced a relative change in generalantisocial behaviour of 0.68 of a standard deviation unit.

To give a clearer illustration of the interaction effects, we have inFigure 1 plotted the profiles for the joining, leaving and ‘non-gang groupsbetween Time 1 and Time 2. As can be seen from Figure 1, the profiles forthe gang groups differed markedly from that of the non-gang members.Although the general antisocial behaviour for non-gang members decreasedslightly between T1 and T2, the decrease for the leaving group was clearlymore marked. Similarly, joining a gang between T1 and T2 markedlyincreased the level of antisocial behaviour.

For boys, the size of the effect of leaving on the total scale ofantisocial behaviour was similar to the effect of joining (mean d = 0.72).These results strongly support hypothesis 4 about the facilitative effect ofgang membership. A significant Time x Sex interaction effect was evidentfor changes in gang membership status between Time 1 and Time 2,suggesting that general antisocial behaviour changed more for boys thanfor girls when leaving or joining a gang.

For the violence scale (see the lower panel of Table 5), significantinteraction effects were demonstrated across all events, including joiningbetween T2 and T3. This is further illustrated in Figure 2, whichclearly shows that violent behaviour for the joining group increasedmarkedly between T2 and T3 whereas no behavioural change took placefor non-gang members. Leaving the gang between T2 and T3 was stronglyassociated with reduced levels of violent behaviour.




Table 5 Interaction (time x group) effects for gang members vs. non-gang members with

sex as a covariate: age 13 and age 14 cohorts

d.f. F d

Antisocial behaviourLeaving between T1 and T2 867

(451)48.49

(35.59)T x S 0.91

(1.01)Leaving between T2 and T3 759

(380)35.59

(12.02)0.86

(0.78)Joining between T1 and T2 858

(447)42.87

(35.42)T x S 0.90


(400)0.34 n.s.

(0.32) n.s.0.05

(0.03)

Violent behaviourLeaving between T1 and T2 851

(442)17.93

(8.80)T x S 0.56

(0.50)Leaving between T2 and T3 750

(375)35.57

(46.26)T x S 0.87


(438)50.82

(42.36)0.98


(395)19.58

(20.28)0.60

(0.74)

Notes: Boys’ figures in parenthesis. All F-values are significant at the p < .01 level except n.s.T x S: significant Time x Sex interaction. Effect sizes (d) are estimated from differencescores.

30

25

20

15

10

5

0

Mea

n sc

ale

scor

e

T1 T2

Non-gang

Leaving

Joining

Figure 1 Mean variety scale scores for total antisocial behaviour: Non-gang members,

and gang members joining and leaving between Times 1 and 2.




On average, leaving or joining a gang produced a relative change inviolent behaviour of 0.75 standard deviation units. For boys, the facilita-tion effect was even stronger – nearly one unit of standard deviation. Asignificant Time x Sex interaction effect was evident for leaving a gang atboth time periods (boys’ scores changed more than girls’). In sum, theseresults give strong support to hypothesis 4 and a facilitation effect.

Discussion

Main results

The main goal in the present study was to examine the contribution ofselection and facilitation processes to the frequently demonstrated associa-tions between gang membership and delinquent and violent behaviour.Effects of both processes were demonstrated, in somewhat varying degree,for the two dependent variables.

The cross-group analyses demonstrated that gang members weresignificantly more involved in general antisocial behaviour than were theirnon-gang peers in periods when they were not active gang members(before, between and after periods of gang membership). These resultssupport hypothesis 1 and the presence of a selection effect. The size of thisselection effect was moderate in the sample as a whole, and somewhatstronger for boys when analysed separately. Moreover, the longitudinalanalysis of gang members in active versus non-active periods demonstratedthat they were significantly more involved in antisocial behaviour when

16

14

12

10

8

6

0

Mea

n sc

ale

scor

e

T2 T3

Non-gang

Leaving

Joining

4

2

Figure 2 Mean variety scale scores for total violent behaviour: Non-gang members, and

gang members joining and leaving between Times 2 and 3.




they were active gang members compared with the passive periods. Thisresult is clearly in accordance with hypothesis 4, and gives strong supportto the view that active gang membership facilitates antisocial behaviour. Inline with this, the longitudinal analyses comparing gang members afterjoining or leaving the gang with the non-gang group demonstrated thatgeneral antisocial behaviour in gang members increased after joining a gangand decreased after leaving as compared with the non-gang group. Withthe exception of students joining a gang between T2 and T3, these effectswere strong. In demonstrating selection effects as well as strong socialfacilitation effects with respect to general antisocial behaviour, thus con-firming both hypotheses 1 and 4, these results appear to be most consistentwith the enhancement model.

With respect to involvement in violent behaviour, gang membersagain scored significantly higher than their non-gang peers in periods whenthey were not actively associating with the gang (before, between and afterperiods of gang membership). However, when boys were analysed sepa-rately, the effects at T1 and T3 were not significant, and the cross-groupcomparisons indicated only a small selection effect. The profile analyses, onthe other hand, demonstrated that entering and leaving a gang werefollowed by marked changes in violent behaviour, suggesting a strongfacilitation effect, especially for leaving between T2 and T3 and joiningbetween T1 and T2. Further, the results from analyses of boys separatelyindicated an even stronger facilitation effect for boys than for girls.

Unlike the results for the total scale of antisocial behaviour, thefacilitation effect for violent behaviour was marked also when joiningbetween T2 and T3. Since the total scale of antisocial behaviour includes alarger proportion of less serious types of offending than the violence scale,the absence of a facilitation effect for the former when joining in this periodmay reflect an ageing-out effect. The results may suggest that, for non-violent types of antisocial behaviour, subjects who joined a gang at Time 3(when they were 15 and 16 years old) to some extent were less subject toconformity pressures than were those who joined at younger ages. Hence,age seems to influence what types of antisocial behaviour are facilitated inperiods of active gang membership.

In conclusion, small but significant selection effects were demon-strated for the majority of the cross-group comparisons in violent behav-iour, and the results from the profile analyses strongly supported thepresence of facilitation processes. As in the case of general antisocialbehaviour, these results are most consistent with the enhancement model(hypotheses 1 and 4), although facilitation rather than selection makes thestrongest contribution to the enhanced level of violent behaviour.




Comparing the current results with previous studies

When comparing the results for the total scale of antisocial behaviour withthe results from earlier studies, it is important to bear in mind that thisscale covers mainly items on theft and vandalism. It differs somewhat fromThornberry and colleagues’ ‘general delinquency’ and ‘property offences’scales. The ‘general delinquency’ scale covers a broader range of actscompared with our total scale, and the ‘property offences’ scale is clearlymore restricted. The total scale also differs markedly from Esbensen andHuizinga’s ‘street offences’ and ‘serious offences’, which include moreserious acts. The measure that is most comparable to our total scale isperhaps Esbensen and Huizinga’s ‘minor offences’ and Gordon et al.’s‘property delinquency’.

The significant selection effects shown for the total scale of antisocialbehaviour in the present study run counter to the findings reported fromthe Rochester study. In the latter, a selection effect was found only for the‘general delinquency’ index, which in addition to property offences in-cluded both violence and drug selling. Besides, the selection effect wasweak and restricted to stable gang members. In the Denver study, sig-nificant selection effects were reported only for ‘street offences’ and ‘seriousoffences’ (both including violence), but the ‘minor offences’ index used inthe Denver study was not subject to separate analyses of selection effects.On the other hand, the Pittsburgh study reported selection effects for‘property delinquency’ quite similar to those found in our study.

In addition, the strong facilitation effects demonstrated for the totalscale of antisocial behaviour differ somewhat from the findings in theRochester study. In Thornberry et al.’s (1993) study, a strong facilitationeffect was found for all the included indices, with the exception of the‘property offences’ index, which did not show systematic variation withgang membership. The facilitation effect for the total scale of antisocialbehaviour found in our study seems to be more consistent with the resultsfrom the Denver study, where facilitation effects were found for all theoffending categories. Unfortunately, separate analyses of facilitation effectswere not performed on the ‘minor offences’ index in that study. Again, thefacilitation effects in our study are largely comparable to those reported inthe Pittsburgh study.

Turning to violent behaviour, both the small selection effects and themoderate to strong facilitation effects demonstrated in the present studyseem to be more consistent with the results from prior studies. The resultsfrom the Denver study (Esbensen and Huizinga 1993), the Montreal study(Lacourse et al. 2003) and the Seattle study (in Thornberry 1998) demon-strated that gang members were only marginally more involved in violent




behaviour in non-active periods compared with their non-gang peers. Asnoted above, a small selection effect was identified in the Rochester study(Thornberry et al. 1993) on the ‘general delinquency’ index for the stablegang members. Re-analyses of this panel study including data from year 4(Thornberry et al. 2003) also showed a small selection effect for violentdelinquency. Also, the results from the Pittsburgh study, as well as analysesof risk factors reported from the Rochester study and other studies (Hill etal. 1999; Lahey et al. 1999), suggest that some selection effect for violentbehaviour may be present in gang members.

The relatively large selection effect demonstrated for general anti-social behaviour in this study and in the Pittsburgh study compared withthe smaller effect reported from the Rochester study could reflect either (1)discrepancies in the content of the measures used, (2) differences in theapplied analytical techniques, or (3) differences in sample characteristics.As noted above, our total scale of antisocial behaviour differs some-what from Thornberry et al.’s (1993) ‘general delinquency’ and ‘propertyoffences’. It seems, however, that conceptual differences in the criterionvariables are not large enough to account for the different findings.

The prevalence of gang membership in this study was not lower thanin previous studies. Although the criterion for gang membership by andlarge was comparable across the studies, the addition of the term ‘group’ tothe gang questions in our study may have widened the meaning of thequestions slightly. Given the unique meaning of the word ‘gang’ forAmerican youth (Esbensen et al. 2001), this addition may have led to aslight over-inclusion of gang members and a more heterogeneous sample ofgang members. This could partly explain the low involvement in violenceby gang members in our study, but it is also likely that violence is lesscommon among Norwegian adolescents compared with North Americanyouth in general.

Turning to differences in analytical techniques, the earlier studiesmerely reported on levels of significance for relatively small samples in theircross-group analyses. In the present study (as well as in the PittsburghStudy), sub-groups of gang members with similar gang status were joinedto form larger units for analysis, reducing the probability of Type I errors.Analyses of a large number of sub-groups with small n’s, as in theRochester Study, not only affect the true alpha level but also clearly reducethe power of the analyses. Estimates of effect sizes, on the other hand,provide information on the strength of the effects. Not only are effect sizesindependent of group sizes, they also enable a more direct comparison ofeffects across studies.

With respect to sample characteristics, the age groups were largelycomparable across the studies, all of which involved only adolescents in




their early- and mid-teens. However, in contrast to earlier studies, thepresent study (and to some extent the Pittsburgh study) was conducted ona largely representative sample of adolescents from a non-gang city.Becoming a gang member in a mid-sized city in Norway may be a moreextreme choice than becoming a gang member in a high-risk area. Hence,the observed differences in selection effects could reflect a higher thresholdfor joining a gang in this study.

Conceptual considerations and theoretical implications

Since self-reported gang membership and general antisocial and violentbehaviour are highly correlated phenomena, it may be argued that they aremerely different reflections of the same underlying dimension within aperson, and that joining or leaving a gang would not cause changes inantisocial behaviour. This claim is a logical consequence of Gottfredsonand Hirschi’s assertion that self-reported peers’ delinquency ‘may merely beanother measure of self-reported delinquency’ (1990: 157). We do notshare this concern for two reasons. First, gang membership as measured inour study is a state (an aspect of being), whereas antisocial behaviour is aset of actions (an aspect of doing). Although the two variables correlate,they are conceptually different. Second, and related to the first, theobserved overlap between gang membership and antisocial behaviour is farfrom perfect, and self-reported gang membership does not assume involve-ment in general antisocial or violent behaviour. In fact, a number ofstudents who were active gang members did not report any antisocialinvolvement. This was particularly true for violent behaviour, in which themajority of the gang members were not involved.

So far, the results are reviewed in the context of the three explanatorymodels – the selection model, the social facilitation model and the enhance-ment model – but the findings also have implications for traditionaltheories of criminal and analogous behaviour. Gottfredson and Hirschi’s(1990) General Theory of Crime and social learning theory (Akers 1985,1997) have offered different explanations of the strong gang–crime rela-tionship, and they differ markedly in their beliefs in the gang’s potentialto change its members’ level of antisocial behaviour. Gottfredson andHirschi’s theory does not anticipate an independent main effect for crimeopportunity beyond its interaction with low self-control. Consequently,they claim that the criminal influence of the gang generally is small, owingto the fact that the gang primarily attracts persons lacking self-control. Ourresults for general antisocial and violent behaviour give little support toGottfredson and Hirschi’s notion. Not only does the theory have difficultiesin explaining the relatively large behavioural changes following changes in




gang membership status, but the small selection effects on violent behav-iour also run counter to the theoretical predictions. Still, a more direct testof the theory’s assumptions would involve an examination of how self-control interacts with gang membership across time.

In contrast to control theories, social learning theory recognizes theantisocial peer group and the gang as major independent factors affectingthe onset, continuation and termination of the subject’s antisocial behav-iour. This theory does not exclude the possibility of social selection – bothselection and social facilitation processes may be operative – but it empha-sizes facilitation effects over selection effects in explaining the associationbetween gang membership and antisocial behaviour. Our findings areencouraging for social learning theory in demonstrating moderate tostrong facilitation effects, particularly in the case of violent behaviour. Theresults for antisocial behaviour clearly are compatible with combined orintegrated models.

Compared with either control or social learning theories, inter-actional theory (Thornberry 1987) claims to have a less static view on theprocesses linking gang membership to antisocial behaviour. Althoughthe interactive process cannot be studied directly in our longitudinal design,our results suggest that selection and facilitation processes work in areciprocal manner. At least some of the gang members seem to be ‘differentkinds’ of people, with a stronger orientation toward general antisocialbehaviour than their non-gang peers before they join a gang. According tothis theory, weakened social constraints against deviant behaviour increasethe risk of seeking out others with a similar orientation to form gangs orgroups. Once gangs are formed, the interaction with these peers furtherfacilitates and stimulates these behaviour tendencies.

Limitations of this study

Although this sample is largely representative of Norwegian adolescents, itstill needs to be recognized that the ability to generalize from these findingsis limited to the lower age continuum of the adolescent period (ages13–16). Furthermore, and principally owing to the lower number of femalegang members in the study, separate analyses of girls were not performed.Still, the analyses indicate that gang membership is less facilitative ofviolent behaviour among girls than among boys. This result may reflect astatistical bias associated with the higher prevalence of boys’ violentbehaviour and, until future studies have addressed this issue covering largeenough cohorts of male and female gang members, this finding remainssuggestive. Furthermore, the Olweus Bullying Prevention Programme in-troduced between Time 1 and Time 2 in this study may have affected the




results somewhat. It has been demonstrated that the anti-bullying pro-gramme reduced the overall level of antisocial and violent behaviour onthe second and third measurement occasions. This may have reduced theproportion of students joining antisocial gangs as well as the magnitude ofthe behavioural changes associated with changes in gang membership.

Conclusion

The current study has shown the facilitative effects of active gang member-ship on antisocial as well as violent behaviour, and most of these effectswere quite strong. When young people joined a gang (except when this wasbetween T2 and T3), their levels of violent and antisocial behaviourincreased markedly; when they left a gang, this was followed by a markeddecrease. The marked facilitation effect demonstrated in the present studyfits well with previous studies in the case of violence, but less well in thecase of general antisocial behaviour.

The present findings suggest that the association between gang mem-bership and antisocial behaviour is considerably influenced by selectionprocesses, and in this respect they differ markedly from the findings ofearlier studies. Individuals with an antisocial orientation tend to seek thecompany of similar individuals in addition to being influenced by membersof the gang. These results are more in line with recent findings from thePittsburgh study and with the previous findings from studies of risk factorsfor joining antisocial gangs.

It was found that the students who joined gangs were more involvedin violent behaviour, too, than were their non-gang peers in periods prior toand after active gang membership. However, these selection effects in thecase of violent behaviour were markedly smaller than for antisocial behav-iour, and two of the comparisons were non-significant when the malesample was analysed separately. These results indicate that the magnitudeof selection effects is contingent upon the dependent variable in question.

Appendix

Total scale of antisocial behaviour (17 items)

Avoided paying for such things as movies, bus or train ride, or food?Scribbled on the school building, outside or inside, or on things belonging to yourschool?Stolen money or other things from members of your family?Cursed at a teacher?




Taken things worth less than NKr.200 from a store without paying?Skipped one or two lessons?Purposely destroyed or broken such things as windows, benches, telephone booths, ormailboxes?Without permission taken a bicycle or a moped that did not belong to you?Skipped school a whole day?Had a violent quarrel with a teacher?Signed someone else’s name to get money or other things you wanted?Purposely broken chairs, tables, desks, or other things in your school?Purposely destroyed seats in a bus, a movie theatre, or other places?Taken things worth more than NKr.200 from a store without paying?Broken into a shop, house, or apartment and taken something?Broken into a parking meter or the coin box of a pay phone?Stolen a wallet or purse while the owner wasn’t around?

Violence scale (5 items)

Got into a fight at a private party?Got into a fight in a public place (in the street, at a club or in a similar place)?Beaten someone up so badly they probably needed a doctor?Been noisy and rowdy in a public place (in the street, at a club or in a similar place)?Taken part in a fight with the police?

Acknowledgements

This research was supported by grants from the Norwegian Council for Research (NFR)to Mons Bendixen and Dan Olweus and grants to Dan Olweus from the NorwegianPublic Health Association, the Norwegian Ministry of Children and Family Affairs(BFD) and, in earlier phases, the Norwegian Ministry of Education – these grants aregratefully acknowledged. We would also like to thank Terrence P. Thornberry forcommenting on an earlier draft of this paper.

References

Akers, R. L. (1985). Deviant behavior: A social learning approach, 3rd edn.Belmont, CA: Wadsworth.

Akers, R. L. (1997). Criminological theories: Introduction and evaluation, 2nd edn.Los Angeles, CA: Roxbury Publishing Company.

Bendixen, M. and Olweus, D. (1999). Measurement of antisocial behaviour in earlyadolescence and adolescence: Psychometric properties and substantive find-ings. Criminal Behaviour and Mental Health 9, 323–54.

Bjerregaard, B. and Smith, C. (1993). Gender differences in gang participation,delinquency, and substance use. Journal of Quantitative Criminology 9,329–55.




Cohen, J. (1977). Statistical power analysis for the behavioral sciences, revised edn.New York: Academic Press.

Cortina, J. M. and Nouri, H. (2000). Effect size for ANOVA designs. SageUniversity Papers Series on Quantitative Applications in the Social Sciences,series no. 07–129. Thousand Oaks, CA: Sage.

Curry, G. D. and Decker, S. H. (1998). Confronting gangs. Los Angeles, CA:Roxbury Publishing Company.

Elliott, D. S. and Menard, S. (1996). Delinquent friends and delinquent behavior:Temporal and developmental patterns. In J. D. Hawkins (ed.) Delinquencyand crime: Current theories, 28–67. Cambridge: Cambridge UniversityPress.

Elliott, D. S., Huizinga, D. and Ageton, S. S. (1985). Explaining delinquency anddrug use. Beverly Hills, CA: Sage.

Esbensen, F.-A. and Huizinga, D. (1993). Gangs, drugs, and delinquency in a surveyof urban youth. Criminology 31, 565–89.

Esbensen, F.-A., Winfree, L. T., Jr, He, N. and Taylor, T. J. (2001). Youth gangs anddefinitional issues: When is a gang a gang, and why does it matter? Crime andDelinquency 47, 105–30.

Gordon, R. A., Lahey, B. B., Kawai, E., Loeber, R., Stouthamer-Loeber, M. andFarrington, D. P. (2004). Antisocial behavior and youth gang membership:selection and socialization. Criminology 42, 55–87.

Gottfredson, M. R. and Hirschi, T. (1990). A general theory of crime. Stanford, CA:Stanford University Press.

Henry, B., Moffitt, T. E., Caspi, A., Langley, J. and Silva, P. A. (1994). On the‘Remembrance of things past’: A longitudinal evaluation of the retrospectivemethod. Psychological Assessment 6, 92–101.

Hill, K. G., Howell, J. C., Hawkins, J. D. and Batting-Pearson, S. R. (1999).Childhood risk factors for adolescent gang membership: Results from theSeattle Social Development Project. Journal of Research in Crime andDelinquency 36, 300–22.

Hill, K. G., Hawkins, J. D., Catalano, R. F., Kosterman, R., Abbott, R. andEdwards, T. (1996). The longitudinal dynamics of gang membership andproblem behavior: A replication and extension of the Denver and Rochestergang studies in Seattle. Paper presented at the annual meeting of theAmerican Society of Criminology, Chicago.

Huang, B., Kosterman, R., Catalano, R. F., Hawkins, J. D. and Abbott, R. D.(2001). Modelling mediation in the etiology of violent behavior in adoles-cence: A test of the social developmental model. Criminology 39, 75–107.

Kandel, D. B. (1978). Similarity in real-life adolescent friendship pairs. Journal ofPersonality and Social Psychology 36, 306–12.

Klein, M. W. (1984). Offence specialization and versatility among juveniles. BritishJournal of Criminology 24, 185–94.

Klein, M. W. (1995). The American street gang: Its nature, prevalence, and control.New York: Oxford University Press.

Lacourse, E., Nagin, D., Tremblay, R. E., Vitaro, F. and Claes, M. (2003).Developmental trajectories of boys’ delinquent group membership and facili-tation of violent behaviours during adolescence. Development and Psychopa-thology 15, 183–97.

Lahey, B. B., Gordon, R. A., Loeber, R., Stouthamer-Loeber, M. and Farrington,




D. P. (1999). Boys who join gangs: A prospective study of predictors of firstgang entry. Journal of Abnormal Child Psychology 27, 261–76.

Olweus, D. (1991). Bully/victim problems among schoolchildren: Basic facts andeffects of a school based intervention program. In D. Pepler and K. H. Rubin(eds) The development and treatment of childhood aggression, 411–48.Hillsdale, NJ: Erlbaum.

Olweus, D. (1993a). Bullying at school: What we know and what we can do.Oxford: Blackwell Publishers.

Olweus, D. (1993b). Victimization by peers: Antecedents and long-term outcomes.In K. H. Rubin and J. B. Asendorpf (eds) Social withdrawal, inhibition, andshyness in childhood, 315–41. Hillsdale, NJ: Erlbaum.

Olweus, D. (1994). Annotation: Bullying at school: Basic facts and effects of aschool based intervention program. Journal of Child Psychology and Psy-chiatry and Allied Disciplines 35, 1171–90.

Olweus, D. (2005). A useful evaluation design, and effects of the Olweus BullyingPrevention Program. Psychology, Crime and Law 11, 389–402.

Olweus, D. and Alsaker, F. D. (1991). Assessing change in a cohort longitudinalstudy with hierarchical data. In D. Magnusson, L. Bergman, G. Rudinger andB. Torestad (eds) Problems and methods in longitudinal research, 107–32.New York: Cambridge University Press.

Rowe, D. C., Woulbroun, E. J. and Gulley, B. L. (1994). Peers and friends asnonshared environmental influences. In E. M. Hetherington, D. Reiss andR. Plomin (eds) Separate social worlds of siblings: The impact of nonsharedenvironment on development, 159–73. Hillsdale, NJ: Erlbaum.

Spergel, I. A. (1990). Youth gangs: Continuity and change. In M. Tonry andN. Morris (eds) Crime and justice: A review of research, vol. 12, 171–275.Chicago: University of Chicago Press.

Sutherland, E. H. and Cressey, D. R. (1978). Criminology, 10th edn. Philadelphia,PA: Lippincott.

Thornberry, T. P. (1987). Toward an interactional theory of delinquency. Criminol-ogy 25, 863–91.

Thornberry, T. P. (1998). Membership in youth gangs and involvement in seriousand violent offending. In R. Loeber and D. P. Farrington (eds) Serious &violent juvenile offenders: Risk factors and successful interventions, 147–66.London: Sage.

Thornberry, T. P. and Krohn, M. D. (1997). Peers, drug use, and delinquency. InD. M. Stoff, J. Breiling and J. D. Maser (eds) Handbook of antisocialbehavior, 218–33. New York: Wiley.

Thornberry, T. P. and Krohn, M. D. (2001). The development of delinquency: Aninteractional perspective. In S. O. White (ed.) Handbook of youth and justice,289–305. New York: Plenum.

Thornberry, T. P., Krohn, M. D., Lizotte, A. J. and Chard-Wierschem, D. (1993).The role of juvenile gangs in facilitating delinquent behavior. Journal ofResearch in Crime and Delinquency 30, 55–87.

Thornberry, T. P., Krohn, M. D., Lizotte, A. J., Smith, C. A. and Tobin, K. (2003).Gangs and delinquency in developmental perspective. Cambridge: CambridgeUniversity Press.




Thornberry, T. P., Lizotte, A. J., Krohn, M. D., Farnworth, M. and Jang, S. J.(1994). Delinquent peers, beliefs, and delinquent behavior: A longitudinaltest of interactional theory. Criminology 32, 47–83.

Tonry, M., Ohlin, L. E. and Farrington, D. P. (1991). Human development andcriminal behavior: New ways of advancing knowledge. New York: Springer-Verlag.

Mons Bendixen

Mons Bendixen is a PhD student in the Faculty of Psychology, University ofBergen. His current position is associate professor in the Departmentof Psychology, Norwegian University of Science and Technology. His mainresearch interests are the measurement and development of antisocialbehaviour in adolescence and aggressive behaviour in intimate [email protected]

Inger M. Endresen

Inger M. Endresen has a doctoral degree in psychology from the Universityof Bergen. She is employed as a senior researcher at the Research Center forHealth Promotion (HEMIL-senteret), University of Bergen. Her researchinterests are the development of empathic responsiveness and [email protected]

Dan Olweus

Dan Olweus has a doctoral degree in psychology from the University ofUmea, Sweden, and is a research professor of psychology affiliated with theResearch Center for Health Promotion, University of Bergen. A major focusof his research has been on the development and reduction/prevention ofbully/victim problems and antisocial behaviour in school. He also has astrong interest in social science research [email protected]




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Mons Bendixen, Inger M. Endresen, and Dan - Sage Publications