Extending the Spectrum Idea: Child Personality,Parenting and Psychopathology

KARLA G. VAN LEEUWEN*, IVAN MERVIELDE, BARBARA J. DE CLERCQ andFILIP DE FRUYT

Department of Developmental, Personality and Social Psychology, Ghent University, Ghent,Belgium

Abstract

The spectrum hypothesis, postulating that differences between referred and non-referred

samples are confined to mean level differences, is elaborated by exploring whether the

covariation between child problem behaviour and its predictors—child personality and

parenting, rated by mothers—is similar in referred (N¼ 205) and non-referred (N¼ 596)

children and whether personality by parenting interactions can be generalized across

samples. Results showed significant mean level differences for all the variables. Both

personality and parenting explained problem behaviour, with some differences in strength

of the effects across samples. Parenting by personality interactions mainly predicted

externalizing behaviour, with benevolence and conscientiousness as the most prominent

moderators. Results confirmed that moderators of problem behaviour operate similarly in

the two samples, thus corroborating the spectrum hypothesis. Copyright # 2006 John

Wiley & Sons, Ltd.

Key words: parenting; child personality; spectrum hypothesis

INTRODUCTION

In research on psychopathology, researchers are still struggling with the question whether

differences between normal and abnormal or clinical samples can be conceived as mainly

qualitative or rather quantitative (Cole & Baker, 2004; Widiger & Samuel, 2005). This

issue is particularly pertinent for research on personality disorders (Livesley & Jang, 2005;

Widiger & Frances, 2002). One of the ways to conceptualize the relationships between

‘normal’ personality variation and psychopathology is referred to as the ‘spectrum

association’ hypothesis (Shiner & Caspi, 2003), which postulates that a disorder is not a

discrete taxon, but rather represents the extreme endpoints of a continuously-distributed

European Journal of Personality

Eur. J. Pers. 21: 63–89 (2007)

Published online 24 November 2006 in Wiley InterScience

(www.interscience.wiley.com). DOI: 10.1002/per.598

*Correspondence to: Karla G. Van Leeuwen, Department of Developmental, Personality and Social Psychology,Ghent University, H. Dunantlaan 2, B—9000 Ghent, Belgium. E-mail: karla.vanleeuwen@UGent.be

Contract/grant sponsor: Flemish Community; contract/grant number: bel96/32.

Copyright # 2006 John Wiley & Sons, Ltd.

Received 24 January 2006

Accepted 10 May 2006

personality dimension or cluster of dimensions (Widiger & Clark, 2000). Recent research

on the relationships between (normal, adaptive) personality dimensions and (abnormal,

maladaptive) personality disorders (Costa & Widiger, 2002) provides evidence for this

continuity or spectrum model. The concept of psychopathy in youth, for example, seems to

be best approached as a particular pattern of normal personality dimensions, rather than a

qualititatively distinct trait (Salekin & Frick, 2005). O’Connor (2002) showed that the

dimensional universes that capture the variance of popular measures of personality and

psychopathology are indeed very similar for clinical and non-clinical populations. Hence if

there are no structural or qualitative differences between clinical and non-clinical samples,

what differentiates clinical from non-clinical samples are mainly mean level differences.

Extending the spectrum hypothesis

The classic formulation of the spectrum hypothesis usually postulates that non-clinical and

clinical samples can be located on the same set of continuous variables as partially

overlapping distributions with a different mean (see Table 1, level 1). The spectrum

hypothesis is further elaborated, when the similarity of the dimensional structure and other

psychometric properties of measures is tested in clinical and non-clinical samples (see

Table 1, level 2). However, this line of reasoning can be extended from the

conceptualization of problem behaviour towards the formulation of theories about the

variables that are associated with problem behaviour. If one agrees that the structure of

problem behaviour in clinical and non-clinical samples can be described by the same set of

dimensions, the next question arising is whether the covariation between problem

behaviour and its predictors is similar in clinical and non-clinical samples (see Table 1,

level 3). This question extends the spectrum hypothesis to include the requirement of

similar covariation among independent and dependent variables and hence verifies whether

the same theoretical relationships apply to clinical and non-clinical samples. Differences

between clinical and non-clinical samples regarding the covariation between independent

variables and problem behaviour can be further differentiated in two types: differences in

strength of the relationship (quantitative differences) and differences in the nature of the

relationship (qualitative differences). Suppose that a theory specifies a positive relationship

between negative parenting behaviour and externalizing behaviour. The extended version

Table 1. Different levels for testing the spectrum hypothesis

Target Basic research question

Level 1 Means Differences in means between referredand non-referred samples?

Level 2 Structure, validity,and reliability

Differences in psychometric propertiesof measures between referred andnon-referred samples?

Level 3 Covariation Differences in (a) the nature, and (b) thestrength of the covariation amongindependent and dependent variablesbetween referred and non-referred samples?

Level 4 Moderation and Mediation Differences in (a) the nature, and (b) thestrength of moderating and mediatingrelationships between referred andnon-referred samples?

Copyright # 2006 John Wiley & Sons, Ltd. Eur. J. Pers. 21: 63–89 (2007)

64 K. G. Van Leeuwen et al.

of the spectrum hypothesis postulates that the relationship between parenting and

externalizing does not depend on the type of sample. In the case that a test shows that this

relationship depends on the sample, it can be stronger (or weaker) in a clinical than in a

non-clinical sample, hence reflecting a difference in strength. However, the parenting-

externalizing relationship could also be present (significant) in the clinical sample but not

in a non-clinical sample or even positive in a clinical sample and negative in a non-clinical

sample. In this last case the parenting-externalizing relationship is qualitatively different in

both samples.

Theories of problem behaviour do not only specify correlations among variables but

often include variables that mediate or moderate the relationship between independent and

dependent variables. The parenting-externalizing relationship can be moderated by (or

depend on) the personality of the child, or parenting can be conceived as a mediator of the

relationship between child personality and externalizing behaviour. Following the same

reasoning, tests of the spectrum hypothesis can also be extended to include tests of

moderator and mediator effects in clinically referred and non-referred samples (see Table 1,

level 4). Statistically, for moderating effects this boils down to a test of a three-way

interaction between child personality, parenting and sample (clinically referred vs. non-

referred). Hence a test of the generalizability of moderator effects across clinical and non-

clinical samples provides an even more stringent test of the spectrum hypothesis.

Rationale for the choice of predictor and outcome variables

Previous research investigating person-environment interactions primarily focused on the

child’s temperament or various specific personality characteristics, instead of relying on a

comprehensive personality taxonomy, such as the Five-FactorModel (FFM). Temperament

traits are believed to capture a broad range of individual differences in infancy, but those

differences constitute only a subset of personality differences in later childhood and

adulthood (Shiner & Caspi, 2003). Although from a theoretical point of view temperament

and personality can be distinguished, because temperament is presumed to be more

determined by biological or genetic factors, the empirical evidence for this distinction is at

best mixed. Several authors have argued and shown that the traditional dimensions of

temperament are closely related to the dimensions of the Five Factor Model (Mervielde &

Asendorpf, 2000; Shiner, 1998; Shiner & Caspi, 2003). For example, the temperamental

trait Surgency is related to Extraversion, Negative affectivity is connected with

Neuroticism, Effortful control can be linked to Conscientiousness (Rothbart & Putnam,

2002), and Withdrawal is related to the personality trait of Neuroticism (Nigg, 2006). As

Caspi, Roberts, and Shiner (2005, p. 454) note ‘temperament and personality traits

increasingly appear to be more alike than different’. Moreover, adopting a FFM personality

framework for the study of person-environment interactions extends classic temperament

based research, because there is growing evidence for developmental continuity between

the adult ‘Big Five’ dimensions and child personality structure, from preschool age through

adolescence (Caspi et al., 2005). For example, cross-cultural studies of parents’ free

descriptions of their own children’s personality revealed substantial support for the

relevance of the five factor structure as a cross-culturally valid model for describing

individual differences in childhood (Kohnstamm, Halverson, Mervielde, & Havill, 1998).

The five broad dimensions of the FFM are commonly labelled as: Neuroticism (the extent

to which the world is experienced as distressing or threatening), Extraversion (the extent to

which the person actively engages the world or avoids social experiences), Openness to

Copyright # 2006 John Wiley & Sons, Ltd. Eur. J. Pers. 21: 63–89 (2007)

Extending the spectrum hypothesis 65

experience (the quality and depth of a person’s mental and experiential life), Agreeableness

(a continuum ranging from warmth and compassion to antagonism) and Conscientiousness

(the extent and strength of impulse control) (Caspi et al., 2005). Several studies provide

evidence for relationships between child or adolescent problem behaviour and

temperament or personality dimensions. The temperamental disposition ‘lack of control’

has been associated with externalizing behaviour, such as hyperactivity and attention

problems, antisocial behaviour and conduct disorder (Caspi, Henry, McGee, Moffitt, &

Silva, 1995). Children with externalizing problems tend to score lower on both effortful

control and on involuntary control (Eisenberg et al., 2001). Agreeableness has been linked

to externalizing problems in non-clinical and clinical samples of children and adolescents

(John, Caspi, Robins, Moffitt, & Stouthamer-Loeber, 1994). Flat affect, passivity and

behavioural inhibition have been identified as contributing to internalizing problems

(Caspi et al., 1995). Neuroticism has been associated with both anxiety and depression

(Millikan, Wamboldt, & Bihun, 2002). A recent review of studies on personality-

psychopathology relationships in childhood and adolescence postulates the following

pattern of associations: low Agreeableness and Conscientiousness are related to CBCL

externalizing behaviour, whereas high Neuroticism and low Extraversion are typical

correlates of internalizing behaviour (Mervielde, De Clercq, De Fruyt, & Van Leeuwen,

2005).

Relatively few examples of interaction effects are reported in the empirical literature,

despite their theoretical importance (Rothbart & Putnam, 2002), and most studies include

temperament to characterize child individual differences. For example, a study of

Oldehinkel, Veenstra, Ormel, deWinter, and Verhulst (2006) showed that parental rejection

increases the relationship between fearfulness and depressive problems in girls, whereas

emotional warmth protects frustrated children from developing internalizing behaviour.

Few studies have examined child problem behaviour as depending jointly on a Five

Factor Model measure of child personality and parenting. O’Connor and Dvorak (2001)

found that specific combinations of personality characteristics and parenting variables

operate as protective or risk factors and hence that parental behaviours only matter for

some kinds of children but not for others. Prinzie et al. (2003) showed that children rated

high on benevolence are shielded from the negative effects of maternal or paternal

overreactivity (the tendency by parents to respond with irritation and/or anger to

problematic behaviour of their children). Children rated low on conscientiousness were

primarily at risk for externalizing problems when exposed to coercive parental behaviour.

Van Leeuwen, Mervielde, Braet, and Bosmans (2004) found evidence for significant

interactions between benevolence and parental negative control, and between

conscientiousness and parental negative control in the prediction of externalizing

behaviour. These interactions were replicable across judges (parental vs. child ratings of

parental behaviour) and across time (a 3-year interval). In addition, the interactions

measured at time one predicted time two externalizing behaviour.

Research linking parenting and child adjustment consistently refers to two primary

parenting dimensions comprising related parental behaviours: (a) Parental support (or

responsiveness) describing the affective nature of the parent-child relationship and

including parental behaviours like involvement, showing interest in the child; (b) Control

(or demandingness) referring to parental efforts to influence the child’s behaviour, by

setting rules and enforcing standards of behaviour (Gallagher, 2002; Maccoby & Martin,

1983). Most studies focus on the negative aspects of parenting, such as coerciveness or

restrictive control, as risk factors for maladaptive child behaviour. However, it is equally

Copyright # 2006 John Wiley & Sons, Ltd. Eur. J. Pers. 21: 63–89 (2007)

66 K. G. Van Leeuwen et al.

important to examine beneficial parenting skills, fostering child adjustment because they

may protect the developing child against emotional and behavioural problems. The present

study includes both a more supportive component of parenting and a restrictive control

dimension.

Whereas the literature regarding parenting by child characteristics interactions

predominantly focuses on externalizing behaviour as the dependent variable, the current

study includes both internalizing and externalizing behaviour as outcome variables.

Previous research suggests a differential pattern of associations between child personality

and parenting on the one hand, and internalizing and externalizing behaviour on the other

hand (Van Leeuwen et al., 2004). Moreover, one of the features of the spectrum model is

the focus on the higher-order structure of phenotypic psychopathology and on broadband

measures of antecedents. Internalizing and externalizing behaviour have been consistently

identified as two common broadband childhood psychopathology factors (Mervielde et al.,

2005).

The present research

In sum, the present study extends previous research through (a) the use of broad-band

personality dimensions to measure child characteristics, that is the Five-Factor Model,

(b) the inclusion of both a support and a restrictive control dimension of parenting, (c) the

choice of both externalizing and internalizing behaviour as the outcome variables, (d) the

assessment of the continuity of moderator effects across referred and non-referred samples

of children. Moreover, the present study assesses moderator effects with the samemeasures

(child personality, parenting and problem behaviour rated by mothers) in both a large

community sample and a sample with children referred to a clinical setting. This allows for

a more sensitive test of moderator effects because it extends the range of values and in

particular the frequency of extreme cases (McClelland & Judd, 1993). Finally, the present

study aims to investigate the spectrum hypothesis and the proposed extensions. First, we

examine mean level differences in parenting and child personality in the two samples.

Taking into account previous research results, we hypothesize that children in the referred

group will display lower levels of benevolence, conscientiousness, emotional stability,

extraversion and imagination. As regards parental behaviour, we expect mothers of

referred children to report more negative control and less positive parental behaviour.

Second, we investigate whether parenting and personality as predictors of internalizing and

externalizing behaviour differ in the two samples. This is accomplished by testing

personality by group and parenting by group interactions in hierarchical multiple

regression analysis, beyond what is predicted by the main effects of personality, parenting

and group. From previous research (Prinzie et al., 2003; Van Leeuwen et al., 2004) we

primarily expect parenting by personality interactions for externalizing behaviour, in

particular between maternal negative control and benevolence or conscientiousness. Each

of the five personality dimensions was included in the analyses because there are only a few

studies investigating interactions with the five personality dimensions of the FFM, that still

need to be replicated.

Third, we examine the role of personality by parenting interactions in the prediction of

problem behaviour and whether these interactions differ for the two groups. In line with the

spectrum hypothesis, it is hypothesized that personality by parenting interactions will not

differ significantly in the referred and non-referred group. If the child personality by

Copyright # 2006 John Wiley & Sons, Ltd. Eur. J. Pers. 21: 63–89 (2007)

Extending the spectrum hypothesis 67

parenting interaction does not depend on the sample, the differences between the two

samples can be conceived as quantitative.

METHOD

Participants

The clinically referred sample consists of 205 mothers and children, the latter were in

psychological or psychiatric treatment at the time they were enrolled as participants in the

study. Children in the sample are 118 boys and 87 girls, 5 to 14 years old (M¼ 9.9,

SD¼ 1.9). The major difference with the non-referred group is that the clinically referred

sample consists of children receiving professional help because of interference of

psychological problems with their own daily functioning or the functioning of people in

their environment (parents, teachers).

Based on the information provided during the intake interview, the children were

assigned to the following broad diagnostic categories: 24.9% manifested externalizing

behaviour, such as lying, aggression and temper tantrums, 21.0% showed anxiety/

depression symptoms, 15.6% suffered from adjustment problems due to major life

stressors, such as divorce or decease of a parent, 11.2% exhibited developmental disorders

such as attention deficit hyperactivity disorder, Tourette syndrome or autism, 9.3%

reported attention or concentration problems, 8.3% presented withdrawn behaviour or

deficits in social skills, 6.8% were referred for eating/sleeping/psychosomatic problems,

1% displayed obsessive/compulsive behaviour, and finally, 0.5% was referred for suicide

attempt or self-injurious behaviour. For 1.5% of the children there was no information

available about the specific reason for psychological counselling. The period of

psychological treatment ranged from 0 to 56 months, with a mean period of 10 months

(SD¼ 10.13).

An examination of educational level showed that 1.49% of the mothers and 2.56% of the

fathers only attended elementary school or special education, 53.23% of the mothers and

54.87% of the fathers completed secondary education, 37.81% of the mothers and 29.23 of

the fathers finished higher education, and 7.46% of the mothers and 13.33% of the fathers

obtained a university degree. This kind of information was not available for 4 mothers and

10 fathers.

The non-referred sample of children is part of a longitudinal study investigating

parenting, personality characteristics and children’s problem behaviour. Subjects were

mothers (N¼ 596) and one of their children aged 7 to 15. The 276 boys and 320 girls, had a

mean age of 10.9 (SD¼ 1.9; range 7–15). Educational levels for both mothers and fathers

are representative for parents in the provinces East and West Flanders: the highest attained

level of education was elementary school or special education for 4.54% of the mothers and

3.93% of the fathers, 57.14% of the mothers and 53.37% of the fathers completed

secondary education, 29.58% of the mothers and 29.40% of the fathers finished higher

education, and 8.74% of the mothers and 13.30% of the fathers obtained a university

degree.

A comparison between referred and non-referred children showed significant

differences in gender and age. The non-referred group included 46.3% boys and the

clinical group 57.6% (x2 (1)¼ 7.73, p¼ 0.005). The mean age of the non-referred children

Copyright # 2006 John Wiley & Sons, Ltd. Eur. J. Pers. 21: 63–89 (2007)

68 K. G. Van Leeuwen et al.

was 10.96 whereas that of the referred group was 9.95, with F(1,799)¼ 47.25, p< 0.001.

Therefore, age and gender will be entered as control variables in further analyses. A

comparison of the curriculum in secondary school (vocational, technical and general

education) of the children in the referred and non-referred groups showed no significant

difference in educational level (x2 (2)¼ 2.51, p¼ 0.285).

Measures

Parental behaviour

Two parenting dimensions, that is positive parenting and negative control, were measured

with the Ghent Parental Behavior Scale (GPBS, Van Leeuwen & Vermulst, 2004). This

self-report measure is based on concepts from Social Learning Theory (Capaldi &

Patterson, 1989; Patterson, Reid, & Dishion, 1992), organizing parenting into well-defined

constructs derived from observable parental behaviour. Subjects rate the frequency of

behavioural items on a 5-point Likert scale ranging from ‘never’ to ‘always’. Validation of

a pilot version of the GPBS led to the conclusion that the five hypothesized constructs

(positive involvement, monitoring, problem solving, structure and positive reinforcement)

appeared to be too heterogeneous. Refinement of the constructs resulted in a new

questionnaire with nine scales: Autonomy, Discipline, Positive parental behaviour, Harsh

punishment, Monitoring, Rules, Ignoring unwanted behaviour, Material rewarding, and

Inconsistent discipline. Factor analyses with oblique rotation showed evidence for two

higher-order factors: ‘positive parenting’ (consisting of the scales positive parental

behaviour, teaching rules and autonomy), and ‘negative control’ (consisting of the scales

discipline, ignoring of unwanted behaviour and harsh punishment) (Van Leeuwen et al.,

2004; Van Leeuwen & Vermulst, 2004). Cronbach alpha’s in the present sample equaled

0.86 for positive parenting and 0.79 for negative control; the correlation between Positive

parenting and Negative control was �0.01 (n.s.) in the non-referred sample and 0.02 (n.s.)

in the referred sample.

Child personality

The Hierarchical Personality Inventory for Children (HiPIC; Mervielde & De Fruyt, 1999)

comprises items that describe the normal range of child personality related behaviour. Five

broad personality domains are measured, dispersed over 18 facets that are hierarchically

organized under the five domains, that is Extraversion (partitioned in the facets Shyness,

Optimism, Expressiveness, Energy), Benevolence (also known as Agreeableness; further

divided into Egocentrism, Irritability, Compliance, Dominance, Altruism), Conscientious-

ness (split into Achievement motivation, Concentration, Perseverance, Orderliness),

Emotional Stability (divided into Anxiety and Self-confidence) and Imagination (also

known as Openness to experience; partitioned into Creativity, Curiosity and Intellect).

Mothers rated the 144 items on 5-point Likert scales. The factor structure of the HiPIC

proves to be highly replicable across both childhood and adolescence (Mervielde & De

Fruyt, 2002). In the present study we obtained Cronbach alpha’s of 0.95 for Benevolence

(N of items¼ 40), 0.94 for Conscientiousness (N of items¼ 32), 0.89 for Emotional

Stability (N of items¼ 16), 0.91 for Extraversion (N of items¼ 32) and 0.91 for

Imagination (N of items¼ 24). The correlations between the personality variables are

modest in size, with a mean correlation of 0.21.

Copyright # 2006 John Wiley & Sons, Ltd. Eur. J. Pers. 21: 63–89 (2007)

Extending the spectrum hypothesis 69

Child problem behaviour

The Dutch version of the Achenbach Child Behavior Checklist (CBCL; Verhulst, Van der

Ende, & Koot, 1996) assesses behavioural and emotional problems in children. Mothers

rated the frequency of 113 problematic behaviours on a 3-point Likert scale. Two

broadband syndromes can be derived from CBCL scores: Internalizing, with items

referring to somatic complaints, social withdrawal, and anxiety/depression; and

Externalizing, including items indexing aggression, hyperactivity, and delinquency. For

Internalizing behaviour (N of items¼ 31) the value of Cronbach’s alpha was 0.89, for

Externalizing behaviour (N of items¼ 33) was 0.92.

Procedure

Third year psychology students were instructed to enlist clinically referred children with

emotional or behavioural problems as part of an assignment for the advanced course on

Personality Psychology at the Ghent University. The students randomly contacted a

psychologist or a psychiatrist, working in outpatient general Mental Health Centers,

Centers for School Counseling, Psycho-medical centers for children with developmental

and learning disorders, psychiatric clinics, private psychotherapy services, or pediatric

units of a hospital. These centres were geographically spread across the Dutch-speaking

region of Belgium. The psychologist or psychiatrist randomly selected one of their clients

to participate in the study. Another child was randomly selected when parents refused to

collaborate.

Exclusion criteria were the presence of a physical disability or a condition of chronic

disease. Written informed consent was given by the psychologist or psychiatrist as well as

by the parents of the children. Students visited the families at home and asked mothers to

complete the CBCL, the HiPIC and the GPBS.

Non-referred children were recruited via randomly selected elementary and secondary

schools. For elementary schools the sample was stratified by province, (East and West

Flanders), region (rural or urban), school type (public/private/catholic schools) and grade

(third, fourth, fifth and sixth year of elementary school). For secondary schools, sampling

was based on province (East and West Flanders), type of curriculum (vocational, technical

and general education) and grade (first and second year of secondary school). A letter

addressed to the parents informed them about the goal and the procedures of the research

project. A trained psychology student, who instructed the family members to

independently complete a series of questionnaires, visited families at home. Both parents

filled out the HiPIC, GPBS and CBCL. In the present study, we only focus on the ratings

provided by the mothers, to enable a joint analysis with the data supplied by the mothers of

the referred group of children.

Statistical analyses

Classic ANOVA’s were carried out in order to check for mean-level differences of group

(clinically referred vs. non-referred children) and gender, and group by gender interactions.

These analyses were primarily carried out to verify whether it would be necessary to

include interactions between gender and the other variables in the hierarchical multiple

regression analyses.

Hierarchical multiple regression analyses (HMRA) were conducted to test the main

hypotheses. Several ‘functional sets’, that is groups of independent variables grouped for

Copyright # 2006 John Wiley & Sons, Ltd. Eur. J. Pers. 21: 63–89 (2007)

70 K. G. Van Leeuwen et al.

logical reasons, are included in different steps of the HMRA (Cohen, Cohen, West, &

Aiken, 2003). Gender and age were consistently entered in Step 1 as control measures. In

Step 2, we entered ‘group’ as a variable, one of the five child personality domains

(Benevolence, Conscientiousness, Emotional Stability, Extraversion or Imagination), and

one of the two parenting dimensions (Negative control or Positive parenting). This step

enables us to investigate independent effects of group, personality and parenting variables.

In Step 3, we entered the interactions between the three predictor variables, that is,

personality by parenting, personality by group and parenting by group. The first interaction

tests whether the effects of parenting depend on child personality (or vice versa) in the

prediction of problem behaviour. The personality by group and parenting by group

interactions indicate to what extent the relationship between personality or parenting and

problem behaviour is different for the clinical and the non-referred group. In step 4, a 3-

way interaction term was entered, that is, personality by parenting by group. A significant

three-way interaction term indicates that the parenting by personality interaction is

different for the clinical and the non-referred groups. That is, it verifies whether the

parenting by child personality interaction depends on or can be generalized across

the referred and the non-referred samples. For testing and interpretation of interactions, we

followed the guidelines by Aiken and West (1991) and Cohen et al. (2003). We applied the

step-down procedure proposed by Aiken and West (1991, p. 105) and dropped non-

significant interactions because strong theoretical grounds for expecting an interaction

were lacking.

The methodology of this study meets some important conditions to enhance the

probability of detecting person-environment interactions, which is difficult in population

samples, because they require substantial variation in both the person and environmental

variables (Rutter et al., 1997). First, in moderated multiple regression research, sample size

is one of the most important single factors affecting power (Aguinis, 1995). In order to

produce a power of 0.80 for detecting small interaction effects, a sample size in the range of

752 and 1056 is needed, with estimated reliabilities of 0.80 for the predictors,

interpredictor correlations between 0 and 0.50 and a squared multiple correlation between

0.20 and 0.50 for the main effects of the predictor variables (Aiken &West, 1991, p. 164).

A possible solution for this problem is to oversample extreme observations of the predictor

variables (Deater-Deckard &Dodge, 1997; McClelland & Judd, 1993), which was realized

in the present study by supplementing a randomly drawn sample (N¼ 600) with a clinically

referred sample (N¼ 205). Both the large number of cases and the inclusion of more cases

at the extremes of the joint distribution of the predictor variables will increase the power for

detecting interaction effects. Second, it is crucial to have measures with good psychometric

properties. The measures used in this study have a solid factor structure and good internal

consistency with Cronbach’s alphas ranging from 0.79 to 0.95.

RESULTS

Mean level group and gender differences

Table 2 shows means, standard deviations and GLM analyses of variance. Significant main

effects of group were observed for each variable. Referred children had significantly higher

mean scores on both internalizing and externalizing problem behaviour compared to non-

referred children. They also scored significantly lower on the personality domains

Copyright # 2006 John Wiley & Sons, Ltd. Eur. J. Pers. 21: 63–89 (2007)

Extending the spectrum hypothesis 71

Table

2.

Category

meansandresultsofGLM

withgroupandgender

Non-referred

Referred

Boys

Girls

Boys

Girls

Group

Gender

GroupX

Gender

M(SD)

M(SD)

M(SD)

M(SD)

Fh2

Fh2

Fh2

Externalizing

9.01(7.65)

6.43(6.05)

16.99(11.24)

12.51(10.67)

112.68a

0.12

28.50a

0.03

2.06

0.00

Internalizing

8.09(6.84)

7.03(5.90)

12.87(8.62)

16.23(9.51)

143.99a

0.15

3.88c

0.00

14.40a

0.02

Benevolence

�0.75(2.71)

0.14(2.42)

�3.55(3.00)

�2.60(3.18)

156.33a

0.17

17.39a

0.02

0.02

0.00

Conscientiousness

12.45(2.63)

13.37(2.65)

10.77(2.61)

12.13(2.71)

45.35a

0.05

27.65a

0.03

1.04

0.00

Emotional

stability

0.58(1.35)

0.40(1.28)

�0.63(1.30)

�1.14(1.49)

160.24a

0.17

9.94b

0.01

2.22

0.00

Extraversion

8.15(2.20)

8.33(2.13)

7.23(2.19)

6.59(2.66)

53.49a

0.06

1.58

0.00

5.01c

0.01

Imagination

11.10(1.68)

11.00(1.80)

10.19(1.86)

10.60(1.91)

20.21a

0.03

1.21

0.00

3.01

0.00

Negativecontrol

2.10(0.52)

2.02(0.53)

2.20(0.42)

2.12(0.47)

6.02c

0.01

3.40

0.00

0.01

0.00

Positiveparenting

4.26(0.40)

4.26(0.38)

4.03(0.48)

4.01(0.45)

50.98a

0.06

0.26

0.00

0.15

0.00

Note:N

non-referredboys¼276,N

non-referredgirls¼320,N

referred

boys¼118,N

referred

girls¼87

ap�0.001;

bp�0.010;

cp�0.050.

Copyright # 2006 John Wiley & Sons, Ltd. Eur. J. Pers. 21: 63–89 (2007)

72 K. G. Van Leeuwen et al.

benevolence, conscientiousness, emotional stability, extraversion and imagination than the

children in the general population sample. As regards the parenting variables, the mothers

of the clinically referred children reported significantly more negative control and less

positive parental behaviour than the mothers of the non-referred children.

Significant gender effects were found for externalizing behaviour, with higher average

scores for boys. Boys scored significantly lower than girls on the personality domains

benevolence and conscientiousness, whereas girls scored significantly lower than boys on

emotional stability. The effect sizes ranged from 0.01 to 0.17 for the effect of group, and

from 0.01 to 0.03 for the effect of gender.

Two significant group by gender interaction effects were present. For internalizing

behaviour, the difference between boys and girls was greater in the referred than in the non-

referred group. For the personality domain extraversion, the difference between boys and

girls was greater in the referred than in the non-referred group.

Correlations

Pearson correlations between age and the independent variables for the total sample were

not substantial: Benevolence: r¼ 0.11 (p< 0.01), Conscientiousness: r¼�0.03 (p¼ n.s.),

Emotional stability: r¼ 0.14 (p< 0.001), Extraversion: r¼�0.02 (p< 0.01), Positive

parenting: r¼ 0.01 (p¼ n.s.), Negative control: r¼�0.04 (p¼ n.s.).

The absolute values of the zero-order correlations between parenting and personality

variables ranged between 0.03 and 0.31, with 8 out of 10 correlations being significant.

Because the size of these correlations is small to moderate, it can be concluded that the

variance of parenting and child personality measures is only partly shared and thus there is

a substantial amount of independence between the two measures.

Covariation of personality and child problem behaviour in referred

and non-referred children

Independent effects of personality

Table 3 reports, as part of the HMRA involving either maternal negative control (top panel)

or positive parenting (bottom panel), the independent effects of the five broad personality

domains on internalizing and externalizing problem behaviour. The results are entirely

consistent across the two panels. Benevolence is significantly related to externalizing and

to a lesser extent to internalizing behaviour, confirming previous research (John, Caspi,

Robins, Moffitt, & Stouthamer-Loeber, 1994; Krueger et al., 1994; Laursen, Pulkkinen, &

Adams, 2002), indicating a negative relationship between this personality factor and

problem behaviour. A similar pattern emerges for conscientiousness. Children scoring high

on this personality factor tend to have far fewer externalizing problems and less

internalizing problems. Taking into account the prominent role of emotional stability in the

development of adult psychopathology, it is important to notice that also for children and

adolescents this personality factor is significantly related to internalizing behaviour and to

a lesser extent to externalizing behaviour. Children rated low on emotional stability show

more internalizing behaviour. Extraversion, as expected, is significantly related to

internalizing behaviour, with lower levels of extraversion associated with higher levels of

internalizing, but not to externalizing problem behaviour. Finally, smaller but significant

and negative relationships of imagination with both internalizing and externalizing

behaviour can be noticed. From these analyses a clear and consistent pattern for the

Copyright # 2006 John Wiley & Sons, Ltd. Eur. J. Pers. 21: 63–89 (2007)

Extending the spectrum hypothesis 73

Table 3. Moderators of Child Problem Behaviour (HMRA)

Child Externalizing behaviour Child Internalizing behaviour

DF B DF B

Panel 1:Maternal negative controlSex, Age 22.96a �0.14b, 0.00 2.57 0.09, 0.01Group, BE, CON 271.21a 0.13c, �0.52a, 0.14a 57.07a 0.79a, �0.22a, 0.09c

BE�CON, GR�BE,GR�CON

19.70a �0.11a, �0.20a, 0.11 3.21c �0.08c, 0.15, �0.11

BE�CON�GR 0.01 1.60

Sex, Age 22.96a �0.20a, �0.02 2.57 0.07, 0.01Group, CO, CON 113.95a 0.53a, �0.28a, 0.20a 53.20a 0.90a, �0.19a, 0.11b

CO�CON, GR�CO,GR�CON

13.30a �0.08b, �0.03, 0.34a 4.58b �0.11b, 0.23b, 0.04

CO�CON�GR 1.24 6.67b 0.20b

Sex, Age 22.96a �0.33a, 0.00 2.57 �0.08, 0.03Group, ES, CON 77.72a 0.58a, �0.10c, 0.23a 185.95a 0.23b, �0.48a, 0.10b

ES�CON, GR�ES,GR�CON

12.45a .00, �.04, .47a 8.89b �.04, �.30a, .10

ES�CON�GR 0.09 0.33

Sex, Age 22.96a �0.30a, 0.00 2.57 0.01, 0.00Group, EX, CON 77.42a 0.75a, 0.05, 0.23a 90.84a 0.63a, �0.28a, 0.14a

EX�CON, GR�EX,GR�CON

11.03a �0.01, 0.06, 0.42a 2.10 �0.02, �0.17c, 0.01

EX�CON�GR 3.79 0.26

Sex, Age 22.96a �0.31a, �0.01 2.57 0.03, 0.00Group, IM, CON 78.68a 0.64a, �0.09c, 0.23a 55.18a 0.81a, �0.14a, 0.10b

IM�CON, GR� IM,GR�CON

11.87a �0.02, 0.07, 0.39a 1.42

IM�CON�GR 6.93b �0.19b 1.98

Panel 2: Maternal positive parentingSex, Age 22.82a �0.16b, 0.00 2.74 0.07, 0.01Group, BE, POS 246.01a 0.13, �0.58a, �0.04 55.67a 0.79a, �0.24a, �.09BE� POS, GR�BE,GR� POS

11.32a 0.08a, �0.23a, 0.11 2.52 0.04, .16c, 0.16c

BE� POS�GR 0.30 0.00

Sex, Age 22.82a �0.23a, �0.03 2.74 0.06, 0.00Group, CO, POS 80.25a 0.56a, �0.32a, �0.08c 50.66a 0.89a, �0.20a, �0.09c

CO� POS, GR�CO,GR� POS

3.38c 0.07c, �0.11, 0.09 4.90b 0.06, 0.25b, 0.14

CO� POS�GR 0.22 0.03

Sex, Age 22.82a �0.37a, �0.01 2.74 �0.10, 0.02Group, ES, POS 41.99a 0.70a, �0.11b, �0.15a 181.08a 0.25b, �0.51a, �0.15a

ES� POS, GR�ES,GR� POS

1.54 9.26a 0.11b, �0.27a, 0.16c

ES� POS�GR 0.00 4.82c �0.14c

Sex, Age 22.82a �0.35a, �0.01 2.74 0.00, �0.01Group, EX, POS 42.77a 0.85a, 0.07, �0.17a 84.25a 0.66a, �0.28a, �0.12b

EX� POS, GR�EX,GR� POS

2.31 0.03, 0.11, 0.16c 4.56b 0.06, �0.15c, 0.19b

EX� POS�GR 0.84 0.05

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74 K. G. Van Leeuwen et al.

relationships between personality and problem behaviour emerges. Benevolence and

conscientiousness are negatively related to externalizing behaviour and to a lesser extent to

internalizing behaviour. Emotional stability and extraversion are negatively related to

internalizing behaviour and emotional stability is to some extent related to externalizing

behaviour. Finally, children scoring high on imagination tend to present less internalizing

and externalizing problems although the size of this effect is small compared to the effects

of the four other broad-band personality factors.

Consistency of personality effects across referred and non-referred children

The HMR analyses reported in Table 3 show several significant group by personality

interactions, indicating differences in the strength of the relationship between personality

and problem behaviour in the referred and non-referred group (see Table 4). One group by

personality interaction is found with externalizing behaviour as the dependent variable,

that is for the personality domain benevolence. The slopes for the referred and non-referred

group are significant at p< 0.001, the shape of the slopes is similar, and the pattern (see

Figure 1, panel A) of the slopes is identical for analyses with negative control and positive

parenting included.

For four personality domains, an interaction with group is present in the prediction of

internalizing behaviour. The association between benevolence and internalizing behaviour

is significant in the non-referred group and not in the referred group, but only when positive

parenting is included in the analysis. For referred children it doesn’t seem to matter if they

are rated low or high on benevolence: in both cases they score high on internalizing

behaviour, whereas children in the non-referred group show more internalizing behaviour

when they are rated as less benevolent. A similar pattern is present for the

conscientiousness by group interaction: the T-value of the slope for referred children is

not significant (see Table 4). For the emotional stability by group and extraversion by group

interactions the slopes have identical shapes and are significant at p< 0.001. Children

scoring low on emotional stability or extraversion display more internalizing behaviour.

Strictly speaking the spectrum hypothesis postulates a continuum from normal to

abnormal personality and hence only mean level differences between clinical and non-

clinical samples are to be expected. When the slopes of the personality-problem behaviour

regression are significant in both referred and non-referred groups, similar relationships

Table 3. (Continued )

Child Externalizing behaviour Child Internalizing behaviour

DF B DF B

Sex, Age 22.82a �0.34a, �0.02 2.74 0.02, �0.01Group, IM, POS 43.89a 0.71a, �0.10b, �0.15a 52.04a 0.85a, �0.18a, �0.11b

IM� POS, GR� IM,GR� POS

2.70c 0.07c, �0.03, 0.15c 3.34c 0.06, 0.14, 0.16c

IM� POS�GR 0.90 1.44

Note. BE¼Benevolence; CO¼Conscientiousness; ES¼Emotional Stability, EX¼Extraversion; IM¼Imagination; POS¼Positive parenting; CON¼Negative control;ap� 0.0025;bp� 0.010;cp� 0.050.

Via a step-down procedure non-significant interactions were dropped, and therefore only steps with significant

coefficients are reported.

Copyright # 2006 John Wiley & Sons, Ltd. Eur. J. Pers. 21: 63–89 (2007)

Extending the spectrum hypothesis 75

emerge that tend to be somewhat stronger in one of the two groups, depending on the kind

of personality domain and the kind of parenting variable included. In some cases only the

slope for the non-referred children is significant, but it should be noted that in those

cases the interaction is only significant at the 0.05 or 0.01 significance level. From these

results it can be concluded that the majority of the group by personality interactions

indicate a personality-problem behaviour relationship that is similar in form but different in

strength.1

Covariation of parenting and child problem behaviour in referred

and non-referred children

Independent effects of parenting

Negative control as a dimension of parenting is strongly related to the degree of

externalizing behaviour and to a lesser extent to internalizing. As is evident from the

top panel of Table 3, more negative control is consistently related to higher levels of both

types of problem behaviour, irrespective of the effects of the personality variables. The

Table 4. Tests of significance of difference between simple slopes (T-values) for personality bygroup and parenting by group effects

T-values simple slopes

T-valuesInteractionReferred Non-referred

Dependent variable:Externalizing behavior

Third variable

Group�Benevolence with CON �14.55a �15.30a (�)3.34a

with POS �16.59a �16.39a (�)3.82a

Group�Negative control with CO �7.99a 6.16a (�)4.47a

with ES 9.81a 6.50a (�)5.84a

with EX 9.37a 6.69a (�)5.35a

with IM 9.38a 6.78a (�)5.35a

Group� Positive parenting with EX �0.11 �4.07a (�)2.19c

with IM �0.01 �3.59a (�)2.10c

Dependent variable: Internalizing behavior

Group�Benevolence with POS �1.26 �5.14a (�)1.96c

Group�Conscientiousness with CON 0.90 �4.61a (�)3.17b

with POS 0.75 �4.75a (�)3.17b

Group�Emotional stability with CON �13.88a �13.56a (�)4.60a

with POS �12.97a �13.83a (�)3.56a

Group�Extraversion with CON �7.62a �7.30a (�)2.36c

with POS �7.33a �7.13a (�)2.14c

Group� Positive parenting with BE 1.10 �2.04a (�)1.99c

with ES 1.52 �3.73a (�)3.17b

with EX 1.27 �2.92b (�)2.67b

with IM 0.85 �2.58b (�)2.20c

ap� 0.001.bp� 0.010.cp� 0.050.

1In order to check for suppression effects, we looked if parenting by personality interactions differed whenparenting by group interactions were tested separately from personality by group interactions. A few effects were(not) significant compared to the effects reported in Table 3 of the manuscript. Because these differences are verysmall, they are not indicative of suppression effects.

Copyright # 2006 John Wiley & Sons, Ltd. Eur. J. Pers. 21: 63–89 (2007)

76 K. G. Van Leeuwen et al.

bottom panel of Table 3 shows that higher levels of positive parenting are significantly

related to lower levels of internalizing and externalizing problems. However, the strength

of the effect depends on which personality domain is entered together with positive

parenting in the second step of the regression. For example, positive parenting does not

predict externalizing behaviour when it is entered together with benevolence or

conscientiousness. In the prediction of internalizing behaviour there is only a

considerable effect of positive parenting when it is entered together with emotional

stability. Overall the relationships of parenting with problem behaviour tend to be

weaker—indicated by the size of the regression coefficients in Table 3—than these of

personality variables reported in the previous section. Nevertheless the present results

confirm the expected positive relationship of negative control with child internalizing

and externalizing problems but in addition show the negative relationship between

supportive parenting and problem behaviour.

-1

-0,5

0

0,5

1

SD 1- mean SD 1+

Benevolence

gnizila

nretxE

referred

non-referred

-1,00

-0,50

0,00

0,50

1,00

SD 1- mean SD 1+

Emotional stability

gnizila

nretnI

referred

non-referred

Figure 1. Panel A: Interaction between Benevolence and Group predicting Externalizing behaviour. Interactionbetween Emotional Stability and Group predicting Internalizing behaviour.Note: The graphing of the interactions in Figure 1, Panel A is based on a HMRAwith Negative control included;the graphing of the interaction in Panel B is based on a HMRA with Positive parenting included.

Copyright # 2006 John Wiley & Sons, Ltd. Eur. J. Pers. 21: 63–89 (2007)

Extending the spectrum hypothesis 77

Consistency of parenting effects across referred and non-referred groups

The top panel of Table 3 illustrates that the strength of the relationship between negative

control and externalizing behaviour depends on the group. As shown in Table 4, negative

control is more strongly related to externalizing behaviour in the referred group than in

the non-referred group although the slopes for both groups are significant. The pattern of

the slopes is identical when conscientiousness, emotional stability, extraversion and

imagination are included in the analyses. Restrictive parenting generally predicts

externalizing behaviour for all children and adolescents but for referred children the

relationship is somewhat stronger. A group by positive parenting interaction in the

prediction of externalizing behaviour is present when extraversion and imagination are

included. Here the child’s externalizing behaviour in the referred group is high regardless

of the level of positive parenting displayed by the mother. In the non-referred group the

level of externalizing problems is higher for children receiving below mean positive

parenting.

In the prediction of internalizing behaviour, group by positive parenting interactions

are present, when benevolence, emotional stability, extraversion and imagination are

included in the analyses. Table 4 shows that positive parenting is related to internalizing

problems in the non-referred group, with more internalizing problems for children

receiving less positive parenting, whereas this relationship is virtually not present in

the referred group. The patterns of the slopes are identical in all analyses (see Figure 2,

panel B).

In general it can be concluded that the relationship between negative control and

externalizing behaviour is stronger in the referred group than in the non-referred group.

Positive parenting on the other hand is related to reduced internalizing and externalizing

behaviour for the non-referred children, but not for referred children.

Moderator effects of child personality in the relationship between parenting and

child problem behaviour

From Table 3 it can be seen that 8 out of 20 personality by parenting interactions are

significant.3 Benevolence and conscientiousness are the most prominent personality

variables interacting with parenting (6 significant interactions). Externalizing behaviour is

predicted by a benevolence� negative control interaction and a benevolence� positive

parenting interaction, whereas internalizing behaviour is predicted by a benevolen-

ce� negative control interaction. Figure 3 (Panel A) represents the benevolence by

negative control interaction predicting externalizing behaviour with significant slopes for

low (t¼ 6.17, p< 0.001) and mean (t¼ 5.08, p< 0.001) scores on benevolence and a non-

significant slope for high (t¼ 0.98, p< 0.328) scores on benevolence. Figure 3 (Panel B)

graphs the significant interaction of positive parenting with benevolence predicting

externalizing behaviour. Only the slope for low (t¼�2.79, p< 0.01) scorers on

benevolence is significant, not the slopes for mean (t¼�1.33, p< 0.183) and high

(t¼ 1.05, p< 0.292) scorers. The conscientiousness by negative control interaction

predicting externalizing behaviour has significant slopes for low (t¼ 6.25, p< 0.001),

mean (t¼ 6.16, p< 0.001) and high (t¼ 2.92, p< 0.01) scores on conscientiousness. For

the positive parenting interactions with conscientiousness predicting externalizing

behaviour, the slopes for low (t¼�3.00, p< 0.01) and mean (t¼�2.10, p< 0.05) scores

are significant, not for high (t¼�0.19, p¼ 0.847) scores.

Copyright # 2006 John Wiley & Sons, Ltd. Eur. J. Pers. 21: 63–89 (2007)

78 K. G. Van Leeuwen et al.

The interaction effect of negative control by benevolence predicting internalizing

behaviour has significant slopes for low (t¼ 4.40, p< 0.001) and mean (t¼ 3.28,

p< 0.001) scores on benevolence but not for high (t¼ 0.01, p¼ 0.988) scores on

benevolence. The conscientiousness by negative control interaction predicting internaliz-

ing behaviour, is of the same kind with significant slopes for low (t¼ 3.21, p< 0.001) and

mean (t¼ 2.76, p< 0.01) scores on conscientiousness but not for high (t¼ 0.85, p¼ 0.396)

scores on conscientiousness.

Apart from interactions including benevolence or conscientiousness, another two

personality variables were included in significant interactions with parenting. We found a

significant imagination by positive parenting interaction, predicting externalizing

behaviour, with significant slopes for children rated low (t¼�3.89, p< 0.001) or around

the mean (t¼�3.59, p< 0.001) on imagination, but not for children rated high (t¼�1.63,

p¼ 0.103) on imagination. Furthermore, there was an emotional stability by positive

parenting interaction, predicting internalizing behaviour, with significant slopes for low

(t¼�3.54, p< 0.001) and mean (t¼�3.73, p< 0.001) emotional stability, but not for

high scores on this domain (t¼�1.88, p¼ 0.060).

From the results it can be concluded that parenting by personality interactions are more

frequently predicting externalizing (five) than internalizing behaviour (three). Benevolence

is a prominent moderator variable, although it should be noted that only children rated low

or around the mean are at risk for problem behaviour, when also exposed to inadequate

parenting. Conscientiousness is also an important moderator of the effects of both

dimensions of parenting on externalizing behaviour. Children with high ratings on

benevolence, conscientiousness and imagination are protected against inadequate forms of

parenting.

Differences in parenting by personality interactions for referred

and non-referred children

Significant 3-way interactions indicate different parenting by personality interactions for

clinically referred and non-referred samples of children. Three significant 3-way

interactions on a total of 20 tested turned out to be significant. First, the imagination by

0,00

0,50

1,00

1,50

SD 1- mean SD 1+

Negative control

gnizila

nretxE

referred

non-referred

Figure 2. Interactions between Negative control and Group predicting Externalizing behaviour.Note: Figure 2 is based on a HMRA with Conscientiousness included.

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Extending the spectrum hypothesis 79

negative control interaction predicting externalizing behaviour is not significant for the

non-referred group, but only affects externalizing behaviour in the referred group of

children. Referred children scoring low on imagination are more at risk for externalizing

behaviour when they are also exposed to high levels of negative maternal control (t¼ 7.27,

p< 0.001), whereas referred children scoring high on imagination are protected against

externalizing behaviour, even when their mothers show high levels of negative control

(t¼ 2.81, p< 0.01). A significant conscientiousness by negative control interaction

predicting internalizing behaviour is only found in the non-referred group, with significant

slopes for low (t¼ 4.40, p< 0.001) and mean (t¼ 3.28, p< 0.001) levels, and not for high

levels of conscientiousness (t¼ 0.01, p¼ 0.988). A significant emotional stability by

positive parenting interaction predicting internalizing behaviour was only found in the non-

referred sample of children. Non-referred children scoring low (t¼�4.66, p< 0.001) or

around the mean (t¼�4.55, p< 0.001) on emotional stability are at risk for internalizing

behaviour when they are deprived from positive parenting. The slope for non-referred

children scoring high on emotional stability is not significant (t¼�1.02, p¼ 0.309).

-1,00

-0,50

0,00

0,50

1,00

1SD- Mean 1SD+

Negative control

gnizila

nretxE

1SD- BE

Mean BE

1SD+ BE

-1,00

-0,50

0,00

0,50

1,00

1SD- Mean 1SD+

Positive parenting

gnizila

nretxE

1SD- BE

Mean BE

1SD+ BE

Figure 3. Panel A: Negative control by Benevolence predicting Externalizing behavior. Panel B: Positiveparenting by Benevolence predicting Externalizing behavior.

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80 K. G. Van Leeuwen et al.

The finding that only three out of 20 possible three-way interactions are significant,

suggests that in general, there are few differences between referred and non-referred

groups of children in the way personality and parenting interact. Moreover the three cases

show inconsistent interaction patterns, one showing a personality by parenting interaction

for the referred group and the two others a significant interaction for the non-referred

group.2

DISCUSSION

In this study we elaborated and investigated the ‘spectrum association’ (Shiner & Caspi,

2003) postulating that differences between normal and abnormal or clinical samples are

restricted to quantitative or mean level differences on the relevant domains of functioning

(Costa & Widiger, 2002; Widiger & Clark, 2000). We explored in a general population

sample supplemented with a sample of clinically referred children to what extent

(a) differences between referred and non-referred children are confined to mean level

differences, (b) the covariation between child problem behaviour and its predictors—child

personality and parenting—is similar for referred and non-referred children and

(c) personality-parenting interactions can be generalized across both samples. Results

demonstrated (a) mean differences between the referred and non-referred group, indicating

that the mothers of the referred children rated their children lower on the Five Factor Model

personality dimensions, whereas on the other hand they reported higher negative control

and lower positive parental behaviour; (b) that personality and parenting predict child

problem behaviour, showing some differences in the strength of the relationships for

referred and non-referred groups, but not in the kind of relationship; (c) that similar

personality-parenting interactions are associated with problem behaviour in both the

referred and non-referred group. In brief, these results corroborate the spectrum hypothesis

implying that differences between the two types of samples can be conceived as

quantitative rather than qualitative.

Evidence for the spectrum hypothesis

Our data support the classic formulation of the spectrum hypothesis, referring to the fact

that non-clinical and clinical samples can be located on the same set of continuous

variables as partially overlapping distributions with a different mean. This was shown by

the significant mean level differences for problem behaviour, child personality and

parenting between the referred and non-referred samples.

To a certain extent we found evidence for our extended version of the spectrum

hypothesis, stating that the covariation between personality, parenting and problem

2In order to prevent chance capitalization in finding moderator effects, a Bonferroni correction can be applied.This implies that the alpha level for each individual test needs to be lowered to 0.0025 in order to adjust the overallalpha level to 0.05. For the consistency of parenting effects across referred and non-referred groups, theinteractions reported in the bottom part of Table 3 are not significant. However, this correction does not takeinto account the number of significant interactions (four out of five interactions predict internalizing behaviour,and two out of five predict externalizing behaviour). For the moderator effects of child personality, only twointeractions remain significant, i.e. the benevolence by negative control interaction and the benevolence bypositive parenting interaction, both predicting externalizing behaviour. For the three 3-way interactions the p-values do not meet the standard of 0.0025 to adjust the overall alpha level to 0.05 and therefore they can beconsidered as negligible.On the other hand, one could argue against the Bonferroni correction, because it is tooconservative.

Copyright # 2006 John Wiley & Sons, Ltd. Eur. J. Pers. 21: 63–89 (2007)

Extending the spectrum hypothesis 81

behaviour is invariant across referred and non-referred samples. Our analyses demonstrate

that personality is a strong predictor of child problem behaviour in both the referred and

non-referred, with differential effects of the five domains on internalizing and externalizing

behaviour. Some differences are found in the relationships between personality and

psychopathology across referred and non-referred samples. However, these differences

pertain to the strength and not to the kind of relationship: the shapes of the regression lines

are largely similar for the referred and non-referred sample. If one postulates a weaker

version of the spectrum hypothesis allowing for mean differences and differences in

strength but not for qualitative differences in the relationship between personality and

problem behaviour, then this weaker form of the spectrum hypothesis is supported. Hence

the difference between referred and non-referred groups is quantitative rather then

qualitative. If one wants to build a model for personality-problem behaviour relationships

for referred and non-referred groups, the model would include the same variables, the

path coefficients would indicate the same direction but some of the path coefficients would

turn out to be slightly higher for referred than for the non-referred groups. Although

strictly speaking this is a deviation from the spectrum hypothesis, it is a minor deviation that is

a far cry from the often claimed qualitative differences between referred and non-referred

groups.

As regards parenting as an independent variable, the association between negative

control and problem behaviour was found in both the referred and non-referred group of

children, but the effect was somewhat stronger in the referred group. This result shows that

different statistical analyses can provide different perspectives on the same data set (West,

2003). Analysing exclusively differences in means with GLMwould lead to the conclusion

that negative control is of minor importance in considering differences between referred

and non-referred groups. Although the mean level difference is small for negative control,

this variable was identified as a strong predictor of externalizing behaviour, confirming the

results of previous studies (Barber, 1996; Barber, Olsen, & Shagle, 1994; Deater-Deckard

& Dodge, 1997; Stormshak, Bierman, McMahon, & Lengua, 2000; Weiss, Dodge, Bates,

& Pettit, 1992) and documenting the negative relationship between restrictive parenting

and problem behaviour.

For positive parenting a different pattern emerged. The first-order effects of positive

parenting are weaker than those of negative control and depend on the personality variable

entered in the HMRA. Furthermore the results indicate that lack of positive parenting is

more strongly related to problem behaviour for children in the non-referred group.

Although the levels of significance are small, this effect is present in 6 out of 10 analyses.

This lack of continuity of effects of positive parenting across referred and non-referred

groups might be a challenge for the spectrum hypothesis. However, the results reported

here are preliminary and should be replicated in an independent sample.

Finally, the validity of the spectrum model was tested by assessing whether the

interaction effects of child personality and parenting were sample dependent. In line with

the spectrum hypothesis we did not expect differences in moderator effects across referred

and non-referred samples of children. The results showed a few minor three-way

interactions (3 out of 20), indicating different interactions for the referred and non-referred

children. However when a Bonferroni correction was applied, none of the interactions

remained significant. In sum we can conclude that the documented personality by

parenting effects are largely replicable in both the referred and non-referred group of

children and thus corroborate the spectrum hypothesis implying that similar processes

regulate problem behaviour in both groups.

Copyright # 2006 John Wiley & Sons, Ltd. Eur. J. Pers. 21: 63–89 (2007)

82 K. G. Van Leeuwen et al.

Is testing relations in a clinical versus a non-clinical sample

the optimal test for continuities versus discontinuities in pathology?

Our methodology is in line with the study of O’Connor (2002) who examined structural

differences between personality and psychopathologymeasures in clinical and non-clinical

samples for 37 inventories. Samples were classified as clinical if all respondents received

psychological counseling (inpatients or outpatients), whereas samples were classified as

non-clinical when the data were sampled from the general community or from student

populations. O’Connor discusses the possible inclusion of individuals with psychopathol-

ogy in the non-clinical samples and the presence of normal individuals in the clinical

samples. He concludes that ‘the best available evidence suggests that approximately 15%

of participants in normal volunteer samples meet the diagnostic criteria for psychological

disorders’ (O’Connor, 2002, p. 975). On the other hand, it is to be expected that not all

clinical inpatients or outpatients are prototypically abnormal in terms of DSM-diagnoses. It

is acknowledged that this is a limitation of the present study because it presumably makes

referred and non-referred samples more similar. Nevertheless the documented significant

mean-level differences for internalizing and externalizing behaviour (Table 2) clearly

indicate that the children in the referred group are really more impaired than those in the

non-referred sample.

An alternative test for continuities versus discontinuities in pathology is to divide the

total sample in groups of ‘pure’ internalizers and externalizers based on a cut-off score or

compare groups of children assigned a specific DSM-diagnosis with children without this

specific diagnosis. However, this method poses a statistical problem: identification of

children with a specific diagnosis generates small groups, which reduces the power for

detecting significant interaction effects (Aiken & West, 1991; Cohen, 1988; Irwin &

McClelland, 2003). An even stronger argument against this method is that comparing

groups of children with or without specific diagnoses is not compatible with the spectrum

hypothesis. One of the features of the spectrum model is the focus on the broader, higher-

order structure of phenotypic psychopathology and general broadband conceptualizations of

antecedents. Instead of linking specific disorders with specific antecedents, the main purpose

is to search for the ‘common core’ of psychopathological processes. As Krueger, Caspi,

Moffit, and Silva (1998, p. 216) note, ‘‘mental disorders co-occur at greater than chance rates,

calling into question the meaning of research performed on ‘pure’ cases of disordered

participants. Because of high rates of comorbidity, such pure cases are not only rare, they may

also be unrepresentative of the entire spectrum of persons suffering from the target disorder’’.

Internalizing versus externalizing behaviour

The present study reveals differential relationships between personality and parenting on

the one hand and internalizing and externalizing behaviour on the other hand. It was shown

that benevolence and conscientiousness are negatively related to externalizing problem

behaviour, whereas internalizing behaviour was mainly predicted by low emotional

stability and low extraversion. These results are compatible with the pattern emerging from

studies adopting a person-centered approach (De Fruyt, Mervielde, & Van Leeuwen, 2002;

Van Leeuwen, De Fruyt, & Mervielde, 2004). They demonstrate that resilient children

(scoring above average on all personality domains) display the least amount of

internalizing and externalizing behaviour. Undercontrolled children (scoring low on

benevolence/agreeableness and conscientiousness) tend to show externalizing problems

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Extending the spectrum hypothesis 83

whereas overcontrollers (scoring low on emotional stability and extraversion) mainly show

internalizing problem behaviour.

The relationships between the two parenting dimensions and child problem behaviour

also reveal a differential pattern. Negative maternal control is significantly related to

externalizing behaviour, with high levels of negative control associated with high levels of

externalizing behaviour. There is also a relationship with internalizing behaviour, but the

regression coefficients are smaller, indicating weaker effects. Positive parental behaviour

on the other hand predicts both internalizing and externalizing behaviour but to a lesser

extent than maternal negative control. Overall, negative maternal control is the better

predictor of externalizing behaviour whereas positive parenting is a weaker predictor of

both internalizing and externalizing behaviour. Because both types of parenting have a

different relationship with problem behaviour, these analyses confirm post hoc the

discriminant validity of the parenting dimensions.

The results of this study support the differential susceptibility hypothesis of Belsky

(1997), which assumes that children with different personality profiles also vary in their

sensitivity to parental influences. In particular, children rated high on conscientiousness

and benevolence do not show problem behaviour when exposed to high maternal negative

control and low positive parental behaviour. Being rated low or around the mean on

benevolence or conscientiousness is consistently associated with more problem behaviour,

in particular when children are exposed to inadequate parenting. These findings

corroborate the results of Prinzie et al. (2003), O’Connor and Dvorak (2001) and Van

Leeuwen et al. (2004).

Clinical implications

Although a categorical model, such as the DSM-IV, has the advantage of facilitating

communication between clinicians, a dimensional model may be more appropriate to deal

with co-morbidity and illusive boundaries between diagnostic categories (Widiger &

Samuel, 2005). By focussing only on the most appropriate categorical diagnosis, clinicians

ignore important ‘conditions’ for psychopathology or the ‘broader perspective’ (Mervielde

et al., 2005). This study shows evidence for multiple variables that covary in explaining

psychopathology, that is variables describing characteristics of the person, and parenting as

an environmental influence. This suggests that both parenting and personality variables

should be taken into account in the assessment and for the selection of an appropriate

treatment for children’s externalizing and internalizing behaviour. This implies the need

for standards in order to be able to identify ‘extreme variations’ of the dimensions.

The prospects for treatment of children presenting a similar clinical level of

externalizing may depend on their personality profile. Clinical levels of externalizing

together with low benevolence (and low emotional stability) may be much more difficult to

treat because of the stability (and the presumed genetic basis) of the maladaptive

personality profile. Clinical levels of externalizing without evidence for maladaptive

personality but with evidence for negative parenting suggest an intervention not only with

the child but also with the family system. Assessment of the personality profile of child in

addition to problem behaviour could also be helpful to tailor treatment to the basic

tendencies of the child. A child scoring high on imagination or openness may be more

responsive to changes in parental behaviour or to novel treatments whereas a highly

introverted child may benefit more from personal interaction with a skilled psychotherapist

than from group therapy.

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84 K. G. Van Leeuwen et al.

Limitations of this study and future research

Because this study is the first to compare mean level, covariation and moderator effects of

parenting and personality in referred and non-referred children, replication of this study in

independent samples is warranted to establish the robustness of the effects. These samples

should be large enough to guarantee adequate power to detect 2- or 3-way interactions.

Moreover, the inclusion of longitudinal data would provide the opportunity to compare

effects over time, and hence permit stronger conclusions regarding the direction of the

effects and the causal status of the antecedents of child psychopathology.

Further, it should be noted that item-content overlap between measures of child

personality (HiPIC) and problem behaviour (CBCL) represents a potential problem of

validity. In our study, the instrument used to assess child personality (HiPIC) is conceived

as a multidimensional measure of adaptive or normal individual differences in children that

contains items describing the normal range of child personality related behaviour. On the

other hand, the Child Behaviour Checklist primarily contains items that describe

behavioural and emotional problems. Fortunately some recent studies have addressed the

impact of item-overlap across measures of child temperament and child behaviour problem

(Lemery, Essex, & Smider, 2002; Lengua, West, & Sandler, 1998). These studies showed

that when confounded items were eliminated from both measures, either based on

empirical evaluation of overlap (via exploratory or confirmatory factor analysis) or based

on content evaluation of overlap (via expert ratings of meaning overlap), this did not

seriously affect correlations between child personality and child problem behaviour. A

study by Prinzie, Onghena en Hellinckx (2005) discusses the problem of item overlap

between child personality as measured with the HiPIC and child exernalizing behaviour,

measured with the CBCL. It shows that the link between benevolence and externalizing

behaviour is not due to item overlap, because dropping overlapping items, did not affect the

results.

The results are based on measures completed by the same informant (the mother) and as

such introduce the problem of confounded method-variance.3 Relying on a single reporter

can exaggerate the true relations between parenting and child adjustment (Galambos,

Barker, & Almeida, 2003), and therefore it would be worthwhile to obtain ratings from

more than one informant. Future research should address this issue by collecting data from

fathers in referred samples and or by aggregating scores over parents. Also, attention could

be given to possible differential effects of maternal and paternal parenting on child

psychopathology, and possible gender differences, because previous research has shown

that boys and girls respond differently to parenting practices (e.g. Oldehinkel et al., 2006).

In a strict sense, the design of the present study does not allow to draw conclusions about

recurrent reciprocal interchanges over time between child and parent, as specified by the

transactional effects model explaining child development (Lytton, 1990). Our measures do

not assess child behaviour at time 1, eliciting a certain parental response, which influences

the child at time 2, and so on. This transactional interaction sequence is suggested in

Patterson’s coercion theory (Patterson, 1982; Patterson, Reid, & Dishion, 1992), stating

that a child learns through negative reinforcement that his or her aversive behaviour is an

3In the study we also obtained child ratings of mother’s parenting. The HMRA including child ratings of maternalbehaviour, and mother ratings of child personality and problem behaviour showed replicability of the strongesteffects in Table 3, namely the main effect of negative control in the prediction of externalizing behaviour, thenegative control by group interaction predicting externalizing behaviour, and the benevolence by negative controlinteraction predicting externalizing behaviour.

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Extending the spectrum hypothesis 85

effective strategy to control the behaviour of others and to escape from undesirable

situations. This theory tends to focus on the parental response to the child (Stoolmiller,

2001), and in particular on the fact that some parents are not able to manage their child’s

behaviour. By including child individual characteristics in the present study and

investigating the statistical interaction between parenting and child personality, we have

shown that the effects of parental behaviour on child problem behaviour depend on

certain child characteristics or vice versa. Low benevolence and low conscientiousness

in particular, are related to child unmanageability, a concept that is highly relevant to

coercion theory (Stoolmiller, 2001). Therefore it can be hypothesized that children rated

low on benevolence and conscientiousness evoke increasing levels of negative control from

their mothers, enhancing in return the risk for developing problem behaviour.

CONCLUSION

To our knowledge this study is the first to examine and elaborate the spectrum or continuity

hypothesis by assessing and comparing covariation and moderator effects in referred and

non-referred samples. This innovative way of studying clinical and non-clinical samples

can be applied to other dependent and independent variables. The fact that the present study

generally supports the spectrum hypothesis, contending continuity for the personality-

parenting-problem behaviour relationships across referred and non-referred samples,

obviates the need to invest resources in the development of sample specific models for

understanding and treatment of children’s problem behaviour.

ACKNOWLEDGEMENTS

This study was partly supported by grants from the Flemish Community (No. bel96/32).

The sample of non-referred children in this study was used in Van Leeuwen, Mervielde,

Braet, & Bosmans (2004). This sample was extended with a sample of referred children,

and the present study addresses different and additional research questions than the

abovementioned study.

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