Center for
Developmental
Research
Örebro University, Sweden
Maarten van Zalk, Lauree Tilton-Weaver, Margaret
Kerr, Håkan Stattin, Nejra van Zalk
Overview
 Our main interests
 Current SIENA studies
 Main issues & many wishes
Personal interests
Interests
 Online vs. offline networks (Maarten)
 Personality: psychopathic traits, Big Five (Maarten,
Margaret)
 Externalizing: delinquency, bullying, aggression
(Margaret, Håkan, Lauree)
 Internalizing: depression, social anxiety (Maarten,
Nejra)
 Parents, peers, & externalizing (Lauree)
Data
 Seven Schools: up to 8 friends in the school (N =
2,500)
 Political Socialization Program: Up to 10 friends in
school (N = 4,500)
 10-to-18: large community, up to 23 friends, romantic
partners, and siblings in the community (N = 4,500)
 ONLINE vs.OFFLINE: small community & 89% of
all friends found exclusively online (N = 700)
 ALL data also have independent parental reports
Recent publications

Kerr, M, Van Zalk, M., Stattin, H. (in press). Psychopathic traits moderate
peer influence on delinquency. Journal of Child Psychology and Psychiatry.

Van Zalk, N., Van Zalk, M., Kerr, M. & Stattin, H. (in press). Socialization
of social anxiety in adolescent crowds: Punks, goths, and other eye-catching
peer crowds revisited. Journal of Abnormal Child Psychology.

Van Zalk, N., Van Zalk, M., Kerr, M. & Stattin, H. (2011). Social anxiety as
basis for friendship selection and socialization in a youth social network.
Journal of Personality, 29, 499-525.

Van Zalk, M., Kerr, M.. Branje, S., Stattin, Håkan, & Meeus, W. (2010). Peer
contagion and adolescent depression: The role of failure anticipation. Journal
of Clinical Child and Adolescent Psychology, 39, 837-848.

Van Zalk M., Branje, S. Kerr, M.,Stattin, H., & Meeus, M. (2010). It takes
three: Selection, influence, and de-selection processes of depression in
adolescent peer networks. Developmental Psychology, 46, 927-938.
Issues & Wishes
 Moderation / Interaction effects
 Mediation / Indirect effects
Plotting Simple Slopes
 Y' = b1(x1-x1^) + b2(x2-x2^) + b3((x1-x1^)(x2-x2^))
 b1 = IV (parenting-ego estimate)
b2 = Moderator (delinquency-alter estimate)
b3 = Interaction: parenting-ego×delinquency-alter
estimate
 For x1^ the average parenting score was used
 For x2^ the average delinquency score was used
Moderation

Approach to graphing: Plot simple slopes

Is there a user-friendly way to visualize and test differences between
groups?

Is this the best for two variables with a wide range of values?

Average scores or average for ego/alter?

If only for ego or alters, how do you get this information?

Are ego-alter tables the way to go?

Wish: Function in RSiena that can help visualize interaction effects,
visualize the slopes for the different effects
Mediation
 Processes / mechanisms underlying peer influence
effects
 Crucial for understanding how peer influence works
 Stages in influence
 Indirect effects
Mediation
 Do negative cognitions mediate peer influence on
depressive symptoms?
 Traditional conditions for mediation:
1) X on Y
2) X on Z
3) When X and Z together on Y, only X remains
Mediation
 Do negative cognitions mediate peer influence on
depressive symptoms?
 Recently:
 Indirect effects of X on Y VIA Z
Negative
cognitions
Friends depr
Targets’
depression
Mediation
Depressive symptoms
Cognitions
Behavioral evolution
(influence)
Parameter
s.e.
Parameter
s.e.
Rate period 1
10.1221***
1.79
8.1231***
1.43
Rate period 2
10.2134***
1.89
8.975***
1.31
Linear shape
1.21***
.24
1.45***
.23
Quadratic shape
1.12***
.23
1.81***
.33
Ego’s negative cognitions
.43***
.08
.74***
.12
Average alter
.12***
.74***
Average alt
.04
Negative
cognitions
.12***
.43***
Targets’
depression
Mediation
 Indirect effects of X on Y VIA Z

Can we use a Sobel’s test?

Boots-trapping?
.74***
Average alt
Negative
cognitions
.12***
.43***
Targets’
depression
Overview
 Our main interests
 Current SIENA studies
 Main issues & many wishes