O. Introduction 
0.1. Background of the study 
The data of this handbook are part of the longitudinal study "Individual Development and Social 
Structure" (IDSS), that was taken up in 1976 (Edelstein, Keller & Schröder, 1990). 
The aim of the study was to analyze the developmental trajectories of Icelandic children in 
cognition (Schröder, 1989) and social cognition (Keller & Edelstein, 1991; Keller & Edelstein, 
1993) and to investigate personality dimensions and ego resources (Hofmann, 1991) against 
the background of socialstructural constraints in a society undergoing an accelerated 
modernization process (Björnsson, Edelstein & Kreppner, 1977). 
Figure A specifies the hypothetical relationships between the psychological and the sociological 
dimensions. 
Figure A Hypothetical model of developmental relationships 
Individual Development 
Social Structure 
School 
SSocial 
Cognition 
Cognition 
Sozialization 
+ 
— 
E 
 
Ego