Do Early Difficult Temperament and Harsh Parenting ...

J Abnorm Child Psychol (2006) 34:685–695 DOI 10.1007/s10802-006-9055-6

ORIGINAL PAPER

Do Early Difficult Temperament and Harsh Parenting Differentially Predict Reactive and Proactive Aggression? Frank Vitaro · Edward Dylan Barker · Michel Boivin · Mara Brendgen · Richard E. Tremblay

Published online: 18 October 2006 C Springer Science+Business Media, LLC 2006

Abstract The goal of this study was to examine the links between difficult temperament (i.e., negative emotionality) and harsh parental discipline during toddlerhood, and reactive and proactive aggression in kindergarten. These links were assessed on a longitudinal population-based study of 1516 boys and girls followed longitudinally from the age of 17 months through the age of 72 months. Two possible models were tested to examine the interplay between negative emotionality and harsh parenting in predicting later reactive aggression compared to proactive aggression. The first was an additive model where both aspects make unique contributions in predicting later reactive aggression. The second model was an interactive model where harsh parenting exacerbates the link between negative emotionality and reactive aggression. Results showed a specific contribution of negative emotionality to reactive aggression. The results relative to harsh parenting are more mixed but nonetheless in line with developmental models stressing different pathways to reactive and proactive aggression. Keywords Reactive and proactive aggression . Temperament . Parenting . Longitudinal . Children F. Vitaro () · E. D. Barker · R. E. Tremblay GRIP University of Montreal, 3050 Edouard-Montpetit, Montreal (Quebec), Canada H3T 1J7 e-mail: [email protected] M. Boivin Laval University, Quebec, Canada M. Brendgen University of Quebec at Montreal, Montreal, Canada

Over the past two decades, researchers have emphasized the distinction between reactive and proactive aggression (e.g., Dodge & Coie, 1987) on the basis of their underlying function or motivation. Reactive aggression occurs in response to antecedent conditions of real or perceived provocation, frustration, or threat and is usually accompanied by the expression of anger. It has its roots in the frustration-anger theory of aggression (e.g., Berkowitz, 1962, 1993; Dollard, Doob, Miller, Mowrer, & Sears, 1939). The concept of proactive aggression is more in line with the social learning model of aggression (Bandura, 1973, 1983). According to this notion, proactive aggression is driven by the anticipation of rewards, and hence, is under the control of positive reinforcement, either directly or vicariously (i.e., through modeling). Reactive aggression is instead under the control of negative reinforcement, when successful in turning off the provocation or the threat that triggered it in the first place (Vitaro & Brendgen, 2005). Despite some notable opposition (Bushman & Anderson, 2001), the distinction between reactive and proactive aggression has received considerable support over the past decade. Exploratory and confirmatory factor analyses yielded two distinct factors in line with the reactive-proactive dichotomy, even if the two forms of aggressive behaviors are often manifested by the same individuals (Barker, Tremblay, Nagin, Lacourse, & Vitaro, 2006; Crick & Dodge, 1996; Day, Bream, & Paul, 1992; Little, Jones, Henrich, & Hawley, 2003; Pellegrini, Bartini, & Brooks, 1999; Poulin & Boivin, 2000; Salmivalli & Nieminen, 2002). In addition, distinct correlates and distinct consequences have been linked to reactive and proactive aggression (see Kempes, Matthys, de Vries, & van Engeland, 2005; and Vitaro & Brendgen, 2005, for reviews). One important aspect that has been less examined, however, concerns the possibly distinct etiological factors associated with each type of aggressive behavior. Springer

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Different etiological models The conceptual and methodological distinctiveness of proactive and reactive aggression would be especially highlighted by data showing that their etiology is different. Accordingly, Dodge (1991) has proposed that reactive and proactive aggression originate from different social experiences and develop independently. Specifically, he postulates that reactive aggression develops in reaction to a harsh, threatening and unpredictable environment or abusive and cold parenting, whereas proactive aggression thrives in supportive environments that foster the use of aggression as a mean to achieve one’s goals. In support of this model, reactively aggressive youth show retrospective histories of physical abuse and harsh parental discipline whereas proactively only and proactively-reactively aggressive individuals do not (Dodge, Lochman, Harnish, Bates, & Pettit, 1997). In contrast, proactive aggression seems to be preceded by exposure to aggressive role models in the family who value the use of aggression to resolve conflict or to advance personal interests (Connor, Steingard, Cunningham, Anderson, & Melloni, 2004; Dodge et al., 1997). Proactive aggression also appears to be more linked to positive parent-child interactions and less to controlling discipline than reactive aggression (Poulin & Dishion, 2000). Despite these apparently clear-cut differential links between different aspects of parenting and either reactive or proactive aggression, the small number of studies precludes any definite conclusion at the moment. For example, the possibility of a predictive link between harsh parenting and proactive aggression should not be overlooked because: (a) children who are victimized by their parents may nevertheless learn to use coercive strategies to dominate others (i.e., proactive aggression) through social learning processes, and (b) there is empirical evidence showing that harsh-coercive parenting predicts antisocial behavior, part of which may be proactively oriented (Patterson, DeBaryshe, & Ramsey, 1989). In addition, past studies did not rule out the possibility that the differential links between aspects of parenting and reactive/proactive aggression resulted from third variables such as the child’s difficult temperament. Indeed, specific temperamental dispositions could account for the differential links between parenting and reactive/proactive aggression. To illustrate, children with highly irritable parents may inherit a difficult temperament which (a) may elicit harsh parenting from their highly irritable parents and (b) forecast a propensity for reactive aggression. If this is the case, any subsequent link between harsh parenting and reactive aggression would be accounted for by a common third factor, i.e., difficult temperament. Results showing that infant temperament is highly heritable (Goldsmith, 1996), and that parenting may be a response from parents to the child’s temperament (Bell, 1968; Lytton, 1990) Springer

J Abnorm Child Psychol (2006) 34:685–695

make this scenario plausible. Recently, we have shown that early hostile-reactive parenting is associated with the child’s genotype, and that this association is mediated by the child’s irritable temperament (Boivin et al., 2005; Forget-Dubois et al., submitted) On the other hand, temperamental differences might also be at the root of the distinct etiologies of reactive and proactive aggression. In support of this view, recent empirical evidence shows that reactive aggression, but not proactive aggression in adolescence is predicted by a difficult temperament in childhood (Carrasco Ortiz & del Barrio Gandara, 2006; Vitaro, Brendgen, & Tremblay, 2002). More specifically, reactively aggressive preadolescents were shown to respond with more negative emotionality (i.e., irritability, negative reactivity) to physical and social disturbances than proactively aggressive or nonaggressive peers (who did not differ from each other in that respect) according to mothers when they were 6 years old (Vitaro et al., 2002). Similarly, Carrasco Ortiz and del Barrio Gandara (2006) found a cross-sectional relationship between temperamental difficulties and anger (similar to reactive aggression), but not between temperamental difficulties and proactive oriented physical and verbal aggression,. However, because temperament was assessed at age 6 and at age 11 in these studies, it may have reflected socialization influences as well as personal dispositions. In addition, no interactions involving children’s gender were tested in either study. Consequently the specific roles played by difficult temperament and harsh parenting and their possible interactions with gender remain unknown. Even if harsh parenting does not contribute directly to the prediction of reactive aggression, if could still exacerbate the putative link between a difficult temperament and reactive aggression (i.e., play a moderating role) according to a person-environment interaction perspective, For example, Paterson and Sanson (1999) showed that temperamental inflexibility (a measure that included negative reactivity) and punitive parenting interacted in predicting externalizing behavior problems. Similarly, Hemphill and Sanson (2001) reported that highly irritable 2-year old children who experienced harsh parenting (i.e., low warmth, high punishment) manifested more externalized behavior problems than similarly irritable children who did not experience harsh parenting. However, the studies above did not distinguish between reactive and proactive aggression, nor did they test whether the results applied equally to males and females. Goals of the study The objectives of the present study were: 1) to test whether harsh parenting and temperamental irritability assessed during toddlerhood predict reactive, but not proactive aggression at school entry, and 2) to test whether these differential


predictions are additive or interactive. Temperament is a multi-dimensional construct as it covers self-regulatory capacities, rhythmicity-activity, as well as negative emotionality (Keily, Howe, Dodge, Bates, & Pettit, 2001; Rothbart & Bates, 1998; Sanson, Hemphill, & Smart, 2004). In the present study, only negative emotionality (i.e., irritability and high negative reactivity) was examined, and this, for two reasons. First, only negative emotionality was found to differentially predict reactive and proactive aggression (Vitaro et al., 2002). Second, negative emotionality typically represents a predisposition for anger and frustration (Frick & Morris, 2004; Ledingham, 1991), which should underlie reactive aggression according to the frustration-anger theory of aggression (Berkowitz, 1962, 1993). Gender differences in the roles of harsh parenting and negative emotionality were also expected (Sanson et al., 2004). Given boys’ higher proneness for aggression and their higher vulnerability to harsh parenting compared to girls (Chang, Schwartz, Dodge, & McBride-Chang, 2003), the contribution of harsh parenting to reactive aggression could be stronger for boys than for girls. This view is supported by data showing that hostile child rearing attitudes from mothers during the preschool period were predictive of adolescents’ self-rated hostility for boys but not for girls (Räikkönen, Katainen, Keskivaara, & KeltikangasJärvinen, 2000). In addition, the link between difficult temperament (i.e., negative emotionality) and reactive aggression might also be stronger for boys than for girls because girls may be more pressed by socialization agents to suppress the expression of their difficult temperament than boys. In addition to this study’s potential to contribute to the understanding of the etiology of reactive and proactive aggression, its also includes some novel methodological features. First, given the well established link between low SES and aggression and between low SES and poor parenting (Nagin & Tremblay, 2001), SES was included as a control variable throughout all analyses. Second, past research has usually assessed negative emotionality either too late (i.e., after age 2 years) or too early (i.e., before age 12 months when dimensions of temperament are not yet stable and reliable) (Sanson et al., 2004). In the present study, we collected ratings of negative emotionality from both mothers and fathers when the children were 17 months old. Third, to avoid reliance on only one rater, both mothers and fathers provided ratings on their parenting style. Finally, reactive and proactive aggression scores were based on teacher and mother ratings when the children were 6 years old (i.e., in kindergarten). Hence, in addition to the use of two raters for each construct, we also tried to avoid using entirely the same raters for the predictor and the outcome variables.

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Method Participants Participants were part of an ongoing longitudinal study, the Quebec Longitudinal Study of Children’s Development. The original representative sample of 2223 children (1085 girls and 1138 boys) was selected through a probabilistic sampling procedure using random selection within socio-economic and geographical strata of infants born in 1997–98 in the province of Québec, Canada (Jetté & Des Groseilliers, 2000). Approximately 70% of the original sample participated in the current study (N = 1516, 51% girls; see criterion for inclusion in this study). Of these, 91.5% were Whites, 3% were Blacks, 2.6% were Asiatics, and 2.9% were Native Indians or Inus. The majority (i.e., 79.2%) were living with their two biological parents at the beginning of the study, whereas the remainder were living in reconstructed families or with one parent only (typically with mothers). By age 72 months, when reactive and proactive aggression data were collected, 68.9% of children were still living with both their biological parents. The modal family revenue in Canadian dollars throughout the first 6 years of life was between 49,000 to 59,000 (see details later). Written parental permission was requested at each point of data collection according to the Ethics standards of the University of Montreal and the American Psychological Association (2002). The criterion for inclusion in this study was the presence of teacher and/or mother ratings of reactive and proactive aggression at age 72 months. To examine if missing data at age 72 months was systematically related to the variables employed in this study, we predicted missing and non missing status by the opposite rater and the other variables. For example, we predicted missing in teacher-rated proactive aggression by mother-ratings of proactive aggression, mother-ratings of reactive aggression, gender of the child, negative emotionality, harsh parenting, and family revenue. For both teacher-rated and mother-rated reactive and proactive aggression, the logistic regression models failed to reach significance, suggesting missingness was not related to any of the variables employed in this study. Instruments All instruments were administered either in French or in English. Each instrument that was originally written in English was translated in French using a back translation procedure (i.e., the translated French version was retranslated in English and the two English versions were checked for inconsistencies). The same procedure was applied to the PACOTIS (see later), which was originally developed in

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French, thus ensuring maximum equivalence between the translated and the original versions of each instrument. Temperament Negative emotionality was assessed through the use of six items from the Fussy/difficult scale of the Infant Characteristic Questionnaire (Bates, Freeland, & Lounsbury, 1979) rated by both parents (for 81.2% of the sample) or by mothers and another person who knows the child best (for 18.5% of the sample) when the children were aged 17 months. The six items that were used to create the negative emotionality scale include: 1) how easy to soothe, 2) how often per day fussy, 3) how much fuss/cry, 4) intensity of protest, 5) how easily upset, and 6) how changeable is baby’s mood. Three items from the original 9-item difficult temperament scale (‘dressing’, ‘general mood’, and ‘overall degree of difficulty’) were dropped in favor of a 6-item scale because the latter offered a better face validity to assess negative emotionality and resulted in acceptable Cronbach alphas in the present study (.71 for mothers and .66 for fathers). Each item was rated on a 7-point scale with 1 referring to low negative emotionality and 7 to high negative emotionality. Hence the total score could range between 0 and 42, with a higher score indicative of higher negative emotionality. The correlation between mother and father rating was moderately high, r(1516) = .47. To obtain a more reliable measure and avoid redundancy, we created an aggregate score by averaging mother and father ratings. Harsh parenting Mothers and fathers separately rated their parenting behaviors using the Parental Cognitions and Conduct Toward the Infant Scale (PACOTIS, Boivin et al., 2005) when the children were 17 months old. The PACOTIS is a 23-item scale assessing parents’ perceptions about their self-efficacy and their parental impact in regard to their child’s behavior as well as their tendency to act in a hostile-coercive or overprotective manner towards their child. Only the hostile-coercive (i.e., harsh) parenting scale was used in this study. The seven items of this scale are: “I have been angry with my baby when he/she was particularly fussy”; “When my baby cries, he/she gets on my nerves”; “I have raised my voice with or shouted at my baby when he/she was particularly fussy”; “I have spanked my baby when he/she was particularly fussy”; “I have lost my temper when my baby was particularly fussy”; “I have left my baby alone in his/her bedroom when he/she was particularly fussy”; “I have shaken my baby when he/she was particularly fussy”. Each item could be rated on an 11 point scale, with higher scores indicating more reactive hostility. Cronbach alphas were .70 and .80 for mother and father reports, respectively. There was a moderate correlaSpringer


tion between mother and father ratings of harsh parenting, r(1516) = .27. An aggregate score was computed by averaging the two scores in order to capture both parents’ level of harsh parenting with a single score and hence keep a balance with aggregate scores for other variables. Reactive and proactive aggression Mother and teacher reports of reactive and proactive aggression were collected when the children were 72 months old (i.e., by the end of kindergarten), based on an adaptation of Dodge and Coie’s (1987) questionnaire. Mothers and teachers were asked, “In the past 12-months, how often would you say that your (for mothers)/this (for teachers) child has . . .”. The proactive items were: “Encouraged other children to pick on a particular child”; “Used physical force to dominate other children”; “Scared other children to get what he/she wanted?.” The reactive items were: “When somebody accidentally hurt him/her (such as by bumping into him/her) he/she reacted with anger and fighting”; “Reacted in an aggressive manner when contradicted”; “Reacted in an aggressive manner when teased or threatened”; “Reacted in an aggressive manner when something was taken away from him/her?”. Each item was rated on a 4 point scale, with 0 corresponding to a very low frequency and 3 to a very high frequency. The total score ranged from 0 to 9 for proactive aggression and from 0 to 12 for reactive aggression. Since the wording of the items for the current study was different from the original Dodge and Coie scale (1987), we performed a confirmatory factor analysis (CFA) on teacher and mother reports of reactive and proactive aggression with the Non-Normed Fit Index (NNFI), for which values at about .90 are generally deemed acceptable, and the Root Mean Square Error of Approximation (RMSEA), for which values of less than .08 are deemed acceptable (see Little et al., 2003). Because of non-normality of reactive and proactive aggression scores, Full Information Maximum Likelihood with Huber-White covariance adjustment was used. For teacher-ratings, the CFA showed sound goodness of fit χ 2 (13, N = 966) = 21.19; NNFI = .99; RMSEA = .03. The latent factors of teacher-rated reactive and proactive aggression were significantly correlated (r = .74). The CFA for mother-reports also showed acceptable goodness of fit, χ 2 (13, N = 1492) = 50.95; NNFI = .96; RMSEA = .04. The latent factors of mother-rated reactive and proactive aggression were also significantly correlated (r = .65). For both raters, a two factor model fit the data better than a one factor model (i.e., the Satorra-Bentler Scaled Chis-Square difference was χ 2 (1592, df = 1) = 3.44, p < .0001, for mother ratings, and χ 2 (966, df = 1) = 69.63, p < .0001, for teacher ratings). The correlations between teacher and mother ratings of reactive and proactive aggression, respectively, were .36 and


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.33. This made it possible to create composite scores of reactive and proactive aggression by combining mother and teacher reports for each type of aggression. The internal consistency of the resulting scale was acceptable, Cronbach’s alphas = .66 for proactive aggression and .83 for reactive aggression. Family revenue Family revenue averaged across both data points (i.e., 17 and 72 months) was included as a control variable (Cronbach alpha = .93 across both data points). Family revenue was assessed by asking parents to choose the bracket closest to their total annual family revenue. The range of family revenue was between 1 (less than $10,000), 2 (between $10,000 and $14,999), 3 (between $15,000 and $19,999), 4 (between $20,000 and $29,999), 5 (between $30,000 and $39,999), 6 (between $40,000 and $49,999), 7 (between $50,000 and $59,999), 8 (between $60,000 and $79,999), and 9 (more than $80,000). The median family revenue was between $40,000 and $49,999 (i.e., category 6) at 17months and between $50,000 and $59,999 (i.e., category 7) at 72 months. These values can be considered slightly above average with respect to the earnings of two-parent families in Canada during the data collection period (i.e., 1999–2004).

Results Preliminary analyses Indices of central tendency (i.e., mean and standard deviation) for all the study variables are presented in Table 1, separately for boys and girls. A series of t tests revealed that boys were significantly higher than girls (p < .05) in reactive aggression, harsh parenting, and negative emotionality. Table 1 also includes indices of psychometric properties (i.e., skewness and kurtosis) for each measure. For most of the variables, the normality parameters were within an acceptable range. However, skewness and kurtosis approached Table 1 Summary statistics for girls and boys

non-normality for teacher-ratings of reactive and proactive aggression. Table 2 depicts the correlations of the aggregate subscales for the total sample and separately for girls and boys. In order to test whether the correlations were invariant across gender, we compared a saturated model, where correlations were freely estimated for girls and boys, to a restricted model, where correlations were constrained to be equal across girls and boys. Although the chi-square difference indicated significant gender differences in the correlations between the study variables, χ 2 (1516, DF = 16) = 420.65, p < .0001, inspection of the modification indices revealed that these differences primarily concerned the relation between reactive and proactive aggression, the relations between the independent variables (revenue, temperament, harsh parenting), and the relation between revenue and reactive aggression. The relations between these variables were not central to the research questions, and when the constraints on these particular correlations were relaxed, no other significant differences were found between girls and boys in regard to the correlations among the study variables, χ 2 (1516, DF = 7) = 10.88, p = .14. Analytical procedure Because of the important links between the two types of aggressive behavior we examined the relationship between negative emotionality, harsh parenting, the gender of the child, family revenue, and reactive and proactive aggression by using a joint residual regression model (see Fig. 1). This strategy is similar to that used by Little et al. (2003). In this analysis, we factored-out the common variation between reactive and proactive aggression, and predicted the unique variance associated to each type of aggression in simultaneous regression equations. To achieve the joint residual regression, we imposed the following restrictions: 1) we fixed the scale of the latent factors of reactive aggression, proactive aggression and their common variance to one, 2) we allowed the loadings of the observed reactive and proactive aggression scores on the common variance factor to vary freely, 3)

Gender

Variable

Mean

Std Dev

Skewness

Kurtosis

Girls (N = 773)

Proactive aggression Reactive aggression Harsh parenting Negative emotionality Family revenue Proactive aggression Reactive aggression Harsh parenting Negative emotionality Family revenue

1.08 1.90 3.29 2.62 6.49 1.15 2.67 3.53 2.80 6.44

1.30 1.81 1.90 1.29 2.04 1.46 2.15 2.00 1.40 1.98

1.47 1.09 0.36 0.77 −.56 1.44 0.89 0.31 0.61 −.56

2.45 1.24 −0.47 1.08 −.60 2.15 0.76 −0.46 0.31 −.62

Boys (N = 743)

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J Abnorm Child Psychol (2006) 34:685–695 Table 2

Bivariate correlations between study variables

Number Total Sample (N = 1516) 1 2 3 4 5 Girls (N = 773) 1 2 3 4 5 Boys (N = 743) 1 2 3 4 5 ∗

Variable

1

Proactive aggression Reactive aggression Harsh parenting Negative emotionality Family revenue

1


1


1

2

3

4

.48∗∗∗ 1

.09∗∗ .12∗∗

.09∗∗ .13∗∗ .27∗∗∗ 1

−.09∗ −.16∗∗ −.05 −.03 1

.08∗ .13∗∗

.06 .10∗ .29∗∗∗ 1

−.08∗ −.19∗∗∗ −.07 −.01 1

.09∗ .10∗

.06 .16∗∗ .25∗∗∗ 1

−.11∗ −.14∗∗ −.04 −.04 1

1

.46∗∗∗ 1 1

.51∗∗∗ 1

5

1

p < .05; ∗∗ p < .01; ∗∗∗ p < .001.

we constrained the loadings of the mean scores of reactive and proactive to be equal, and 4) we fixed the error variance of the mean reactive and proactive scores to zero. We first examined an interaction model, and then a marginal effects model. The interactions included: 1) harsh parenting by negative emotionality, 2) gender by harsh par-

Fig. 1 Joint residual regression. C: common variance of reactive and proactive; R: mean teacher and mother reactive aggression; P: mean teacher and mother proactive aggression; ∗ : freely estimated parameter; 1.0: scales of latent factors fixed; a: parameters constrained to be equal; 0: residuals fixed to zero

enting, and 3) gender by negative emotionality. This analysis was implemented in Mplus version 4.0 (Muthén & Muthén, 2006). To accommodate non-normal distributions and to allow inclusion of cases with missing data, Full Information Maximum Likelihood with Huber-White covariance adjustment was used (Muthén & Muthén, 2006).

17-months 72-months 1.0 Negative Emotion. C

* Harsh Parenting

*

*

1.0 1.0

* R

P

*

Controls a

*

* a

* Gender

* *

Measured R

MP Measured P

Revenue

0 Springer

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J Abnorm Child Psychol (2006) 34:685–695 Table 3

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Joint residual regression

Dependent

Predictors

B

SE

95% CI: Lower

95% CI: Upper

b

t

R2 .22

Reactive Harsh parenting Negative emotionality Family revenue Gender

.075 .150 −.137 .647

.025 .037 .024 .091

.027 .077 −.184 .468

.124 .223 −.090 .826

.13∗∗ .17∗∗∗ −.24∗∗∗ .29∗∗∗

3.04 4.01 −5.68 7.09

Harsh parenting Negative emotionality Family revenue Gender

.036 .042 −.05 .032

.016 .024 .016 .062

.004 −.006 −.077 −.090

.068 .089 −.015 .154

.07∗ .05 −.09∗∗ .02

2.22 1.73 −2.94 .52

.02

Proactive

Note. Sample size = 1516. ∗

p < .05; ∗∗ p < .01; ∗∗∗ p < .001.

The interactions were not significant. The results of the marginal effects joint residual regression are presented in Table 3. Twenty-three boys and girls with Mahalanobis Distance scores at a p < .001 were excluded from the analyses, resulting in a sample of 1493 participants (51% girls). First, it is important to note that the correlation between reactive and proactive aggression (r = .48) decreased to r = .06, once the common variance was factored out of the two types of aggression. Second, harsh parenting was significantly and positively associated with both reactive and proactive aggression (bs = .13 and .07, respectively). Negative emotionality, however, was significantly and positively associated only with reactive aggression (b = .17), but not with proactive aggression (b = .05). Child gender was also associated with reactive aggression (b = .29), but not with proactive aggression (b = .02). More specifically, boys manifested higher rates of reactive aggression than girls. Finally, family revenue was inversely related to each type of aggression. To examine if the regression coefficients for the four predictors were significantly higher for reactive aggression than for proactive aggression, we examined the confidence intervals of the unstandardized regression coefficients (see Table 3) and, where appropriate, estimated Wald tests. For child gender and family revenue, the 95% CIs did not overlap, suggesting a clear difference between the associated regression coefficients predicting to reactive aggression and their counterparts predicting to proactive aggression. Harsh parenting, however, equally predicted reactive aggression and proactive aggression (Wald = 2.81, p = .09). In contrast, for negative emotionality, the Wald test indicated a significant difference between the size of the respective regression coefficients predicting to reactive aggression and to proactive aggression (Wald = 9.49, p = .002). In this context, it is also worth mentioning that the R2 —i.e., the proportion of variance explained in each type of aggression by the independent variables—was 22% for reactive aggression but only 2% for proactive aggression. In other words,

the same predictors accounted for 11 times the variance in reactive aggression compared to proactive aggression. To ascertain if the majority of the variance in reactive aggression was attributable to the gender of the child and family revenue, we excluded these two predictors and re-ran the joint residual regression with harsh parenting and negative emotionality as the predictors. The R2 was .09 (41% of .22) for reactive aggression compared to .01 (50% of .02) for proactive aggression. Hence, after accounting for variance attributable to gender of the child and family revenue, negative emotionality and harsh parenting still accounted for 9 times the variance in reactive aggression compared to proactive aggression.

Discussion The objectives of the present study were: 1) to test whether harsh parenting and temperamental irritability (i.e., negative emotionality), assessed during toddlerhood, predict reactive but not proactive aggression at school entry, and 2) to test whether these differential contributions combine additively or nonlinearly (i.e., interactively). With respect to harsh parenting, the results only partially supported our hypothesis, as harsh parenting predicted both types of aggressive behavior. In contrast, the results for negative emotionality were in line with our prediction, as it specifically predicted reactive aggression. There was no interaction between harsh parenting and negative emotionality, thus supporting an additive model in the prediction of reactive and, to a lesser degree, proactive aggression. Harsh parenting As suggested by Dodge (1991), harsh parenting was linked to reactive aggression. However, it was also linked to proactive aggression. In both cases, the contribution of harsh

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parenting was independent of the child’s negative emotionality, despite a bivariate link between harsh parenting and the child’s negative emotionality. Hence, the present longitudinal findings add to the scarce empirical evidence showing that more hostile/abusive family environment contributes to the development or the maintenance of reactive aggressive behaviors. However, they also suggest that a hostile/abusive family environment may contribute to the development or maintenance of proactive aggression. Which mechanisms could account for these links? There is empirical evidence showing that harsh and hostile discipline is related to a biased social information-processing pattern marked by a tendency to selectively focus on cues for threats and to attribute hostile intentions to ambiguous acts (Dodge, Pettit, Bates, & Valente, 1995; Pettit, Dodge, & Brown, 1988). Hence, children exposed to harsh and possibly less predictable parenting may become hypervigilent to cues for threats and readily interpret the intention of the authors of these threats as hostile. These affective and cognitive processes may lower the threshold to react aggressively in order to avoid or escape the punishment that usually follows these cues for threats. This pattern of social cognitive functioning is typical of reactively aggressive children (Crick & Dodge, 1996; Dodge et al., 1997; Orobio de Castro, Veerman, Koops, Bosch, & Monshouwer, 2002) and can be subsumed under the frustration-aggression and the attachment models (Berkowitz, 1993; Crittendon & Ainsworth, 1989). The link between harsh parenting and proactive aggression may also result from social learning processes whereby the child learns to use coercive behaviors to dominate others. Results showing that children who have been abused by their parents tend to have positive outcome expectations for aggression are in line with this interpretation and suggest that positive outcome expectations for aggression acquired from a victim’s perspective can serve as a mediator in this process (Dodge et al., 1995). In other words, the socio-emotional and socio-cognitive mediators through which harsh parenting could be predictively linked to either reactive or proactive aggression could be different although the parenting experience that might trigger them is the same. As such, even if the finding that harsh parenting predicts both types of aggressive behaviors is confirmed in future studies, this does not necessarily contradict the distinctiveness of reactive and proactive aggression with respect to their etiological pathways if, indeed, the underlying mechanisms linking harsh parenting to reactive and proactive aggression are found to be different. As already mentioned, harsh parenting is not the only parenting variable that could be differentially related to reactive and proactive aggression. This is particularly true with respect to proactive aggression, which was only weakly predicted by harsh parenting. Based on Dodge’s model, dimensions of parenting such as unconditional acceptance of Springer


the child’s behavior, unrestrictive parenting, or encouragement/modeling of proactive aggression should play a specific role with respect to proactive aggression. Other aspects linked to parents’ characteristics (i.e., antisocial personality, criminal behavior) may also be more predictive of proactive than reactive aggression because of their potential to influence the child’s attitudes towards the use of violence for self-serving purposes. Unfortunately, these aspects were not assessed in the present study. Showing in the future that these additional predictors are more strongly related to proactive than to reactive aggression would be an important complement to the present study, which focused mostly on factors that were theoretically relevant for reactive aggression. Negative emotionality In line with our expectations, negative emotionality predicted reactive but not proactive aggression. This link may simply reflect the homotypic continuity between negative emotionality and reactive aggression. Specifically, both negative emotionality and reactive aggression involve reactivity to discomfort or perceived threats. They also involve irritability or anger. One could go one step further and suggest that both constructs reflect a general tendency to react to disturbing stimuli, or, alternatively, a low tolerance to frustration, as argued by Vitaro et al. (2002). In any case, this study adds to the scarce evidence linking aspects of a difficult temperament such as negative emotionality, irritability, or low tolerance to frustration specifically to reactive aggression (Carrasco Ortiz & del Barrio Gandara, 2006; Merk, 2005; Vitaro et al., 2002). Since negative emotionality is partly heritable, the (probably direct) link between negative emotionality and reactive aggression suggests that reactive aggression may also be partly under genetic influence (Goldsmith, Buss, & Lemery, 1997; Oniszczenko et al., 2003). This does not preclude, however, that proactive aggression is not also partially under genetic influence but the genes, or the endophenotype at the temperamental level, might be different from those involved in reactive aggression. Recent findings based on teacher-rated proactive and reactive aggression in 6 year-old twin pairs are indeed in line with this tentative conclusion (Brendgen, Vitaro, Boivin, Dionne, & Pérusse, in press). Specifically, in addition to a general genetic disposition to aggression and a general environmental effect that, together, accounted for the overlap between reactive and proactive aggression, the findings from that study also revealed a specific genetic contribution and a specific environmental contribution to both reactive and proactive aggression. Contrary to the results from previous research using global measures of externalizing problems (Hemphill & Sanson, 2001; Leve, Kim, & Pears, 2005; Paterson & Sanson, 1999), no interaction between harsh parenting and negative


emotionality was found in the present study. Methodological differences between the present study and past research could explain why only additive effects of harsh parenting and negative emotionality were found in the present study. First, no other study distinguished reactive from proactive aggression at the outcome level. Second, no studies assessed negative emotionality and harsh parenting at such a young age (i.e., 17 months). In consequence, it is possible that multiplicative effects between both dimensions unfold during childhood whereas additive effects may be operating during toddlerhood. Gender Boys were more reactively aggressive than girls. Given that three out of four reactive items were worded in a way to avoid referring explicitly to physical or verbal/relational aggression, it is unlikely that the difference between boys and girls with respect to reactive aggression resulted from the type of aggressive act reflected in the wording of the reactive items. The observed gender difference may thus be a sign of either biological dispositions or differential socialization experiences. At the biological level, males may be more prone than females to react aggressively when threatened or provoked because they are more impulsive and less refrained by the possible consequences of their reactively aggressive acts (Campbell, 2006). Alternatively, males may be more reactively aggressive than females because their reactive aggressive acts may be more readily tolerated or possibly even reinforced by socializing agents such as parents, teachers, and peers. It is also possible that boys were higher than girls on reactive aggression simply because the former showed higher levels than the latter on the two variables that predicted reactive aggression, i.e., harsh parenting and negative emotionality. In contrast to reactive aggression, girls and boys did not differ with respect to proactive aggression. Given that one out of the three proactive items referred to relational aggression (generally higher in girls) whereas another referred to physical aggression (generally higher in boys) (Crick, Casas, & Mosher, 1997), it is possible that these items cancelled each other out with respect to a difference between boys and girls. A similar lack of difference between boys and girls has been found in other research where proactive aggression items were well balanced with respect to the form of aggressive acts they refer to (e.g., Little, 2002). On the other hand, the lack of consistency in regard to gender differences in reactive and proactive aggression across different studies warrants extreme caution when interpreting these results (Vitaro & Brendgen, 2005). Contrary to our expectations, gender did not interact with either negative emotionality or harsh parenting in predicting reactive aggression. Hence, the present results are not in line with studies that reported differences in males and females

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with respect to the links between negative emotionality and later reactive-like aggressiveness from early childhood to adolescence (e.g., Räikkönen et al., 2000). The present results also contradict previous research showing that schoolaged boys are more vulnerable than girls to harsh parenting (Chang et al., 2003). However, our findings are in line with results reported by Dodge et al. (1997) who found no moderating effect of gender with respect to the link between parental abuse during the preschool years and later reactive, or proactive, aggression. Nevertheless, given that boys were higher than girls on harsh parenting and negative emotionality, the apparent similarity of boys and girls with respect to their vulnerability to these two risk factors may have resulted from their unequal exposure to them. Limitations and strengths The present study has some limitations, which need to be considered while interpreting the findings. First, the number of dimensions assessed in regard to temperament (i.e., negative emotionality) and parenting (i.e., harsh parenting) was limited. Additional measures regarding the child’s disposition towards impulsivity or callousness and regarding parents’ tendency to be lax with respect to discipline or accepting of the use of aggression for accessing resources would allow testing whether these aspects have a specific contribution to proactive aggression. It is not clear, however, whether the assessment of such measures is possible with children as young as the participants of the present study. Second, only one data point was used to assess reactive and proactive aggression. In contrast to temperament and parenting, which are relatively stable during the first 2 or 3 years of life (Grossman, Grossman, & Waters, 2005), aggressive behaviors tend to decline from age 3 onward for most children (Tremblay & Nagin, 2005). This decline is not captured in the one data point collected when the children were age 6 years. Third, the mechanisms through which negative emotionality and harsh parenting during the second year of life are connected to later reactive compared to proactive aggression remain unknown. Finally, although simple and valid, creating composite scores by averaging informants’ ratings may not have been the optimal method to combine ratings from different sources (Piacentini, Cohen, & Cohen, 1992). The above limitations may help explain the modest relationships found in this study between negative emotionality and harsh parenting during toddlerhood and reactive and proactive aggression during early childhood. Indeed, the effect size for the two main predictors (i.e., harsh parenting and negative emotionality) can be considered modest in light of current standards (Cohen, 1977). Nevertheless, together they explained 9% of the variance of reactive aggression, which is rather remarkable considering the use of different raters. In a related vein, the use of a limited number of items to Springer

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assess reactive and proactive aggression can be seen as partially responsible for these modest results and considered as an additional limitation of the present study, although our items correspond in number and content to the widely used Dodge and Coie (1987) items. However, it is important to acknowledge that the six Dodge and Coie (1987) items are not without limitations, which might also apply to the items used in this study. For example, some items describe correlates of reactive/proactive aggression instead of the aggressive behavior and its function. In addition, the proactive aggression scale has a relatively low internal consistency despite an acceptable factor structure. These limitations notwithstanding, our study is the first to show that both negative emotionality and harsh parenting by the second year of life are predictive of later reactive but not proactive aggression. The use of two raters for each measure that are at least partially different with respect to the predictor and the outcome variables adds credibility to the results with respect to the distinction between reactive and proactive aggression. Acknowledgments This research has been made possible through grants from the Quebec Ministry of Heath and Social Services, the Quebec Ministry of Education, the Fonds Québecois pour la Recherche sur la Société et la Culture, and by the Fondation Lucie et André Chagnon. We would like to thank the Institut de la Statistique du Québec as well as the parents and teachers for their participation in this study.

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